xref: /linux-master/kernel/events/core.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Performance events core code:
 *
 *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
 *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
 *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
 *  Copyright  ��  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
 */

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/idr.h>
#include <linux/file.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/hash.h>
#include <linux/tick.h>
#include <linux/sysfs.h>
#include <linux/dcache.h>
#include <linux/percpu.h>
#include <linux/ptrace.h>
#include <linux/reboot.h>
#include <linux/vmstat.h>
#include <linux/device.h>
#include <linux/export.h>
#include <linux/vmalloc.h>
#include <linux/hardirq.h>
#include <linux/hugetlb.h>
#include <linux/rculist.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/anon_inodes.h>
#include <linux/kernel_stat.h>
#include <linux/cgroup.h>
#include <linux/perf_event.h>
#include <linux/trace_events.h>
#include <linux/hw_breakpoint.h>
#include <linux/mm_types.h>
#include <linux/module.h>
#include <linux/mman.h>
#include <linux/compat.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/namei.h>
#include <linux/parser.h>
#include <linux/sched/clock.h>
#include <linux/sched/mm.h>
#include <linux/proc_ns.h>
#include <linux/mount.h>
#include <linux/min_heap.h>
#include <linux/highmem.h>
#include <linux/pgtable.h>
#include <linux/buildid.h>
#include <linux/task_work.h>

#include "internal.h"

#include <asm/irq_regs.h>

typedef int (*remote_function_f)(void *);

struct remote_function_call {
	struct task_struct	*p;
	remote_function_f	func;
	void			*info;
	int			ret;
};

static void remote_function(void *data)
{
	struct remote_function_call *tfc = data;
	struct task_struct *p = tfc->p;

	if (p) {
		/* -EAGAIN */
		if (task_cpu(p) != smp_processor_id())
			return;

		/*
		 * Now that we're on right CPU with IRQs disabled, we can test
		 * if we hit the right task without races.
		 */

		tfc->ret = -ESRCH; /* No such (running) process */
		if (p != current)
			return;
	}

	tfc->ret = tfc->func(tfc->info);
}

/**
 * task_function_call - call a function on the cpu on which a task runs
 * @p:		the task to evaluate
 * @func:	the function to be called
 * @info:	the function call argument
 *
 * Calls the function @func when the task is currently running. This might
 * be on the current CPU, which just calls the function directly.  This will
 * retry due to any failures in smp_call_function_single(), such as if the
 * task_cpu() goes offline concurrently.
 *
 * returns @func return value or -ESRCH or -ENXIO when the process isn't running
 */
static int
task_function_call(struct task_struct *p, remote_function_f func, void *info)
{
	struct remote_function_call data = {
		.p	= p,
		.func	= func,
		.info	= info,
		.ret	= -EAGAIN,
	};
	int ret;

	for (;;) {
		ret = smp_call_function_single(task_cpu(p), remote_function,
					       &data, 1);
		if (!ret)
			ret = data.ret;

		if (ret != -EAGAIN)
			break;

		cond_resched();
	}

	return ret;
}

/**
 * cpu_function_call - call a function on the cpu
 * @cpu:	target cpu to queue this function
 * @func:	the function to be called
 * @info:	the function call argument
 *
 * Calls the function @func on the remote cpu.
 *
 * returns: @func return value or -ENXIO when the cpu is offline
 */
static int cpu_function_call(int cpu, remote_function_f func, void *info)
{
	struct remote_function_call data = {
		.p	= NULL,
		.func	= func,
		.info	= info,
		.ret	= -ENXIO, /* No such CPU */
	};

	smp_call_function_single(cpu, remote_function, &data, 1);

	return data.ret;
}

static void perf_ctx_lock(struct perf_cpu_context *cpuctx,
			  struct perf_event_context *ctx)
{
	raw_spin_lock(&cpuctx->ctx.lock);
	if (ctx)
		raw_spin_lock(&ctx->lock);
}

static void perf_ctx_unlock(struct perf_cpu_context *cpuctx,
			    struct perf_event_context *ctx)
{
	if (ctx)
		raw_spin_unlock(&ctx->lock);
	raw_spin_unlock(&cpuctx->ctx.lock);
}

#define TASK_TOMBSTONE ((void *)-1L)

static bool is_kernel_event(struct perf_event *event)
{
	return READ_ONCE(event->owner) == TASK_TOMBSTONE;
}

static DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);

struct perf_event_context *perf_cpu_task_ctx(void)
{
	lockdep_assert_irqs_disabled();
	return this_cpu_ptr(&perf_cpu_context)->task_ctx;
}

/*
 * On task ctx scheduling...
 *
 * When !ctx->nr_events a task context will not be scheduled. This means
 * we can disable the scheduler hooks (for performance) without leaving
 * pending task ctx state.
 *
 * This however results in two special cases:
 *
 *  - removing the last event from a task ctx; this is relatively straight
 *    forward and is done in __perf_remove_from_context.
 *
 *  - adding the first event to a task ctx; this is tricky because we cannot
 *    rely on ctx->is_active and therefore cannot use event_function_call().
 *    See perf_install_in_context().
 *
 * If ctx->nr_events, then ctx->is_active and cpuctx->task_ctx are set.
 */

typedef void (*event_f)(struct perf_event *, struct perf_cpu_context *,
			struct perf_event_context *, void *);

struct event_function_struct {
	struct perf_event *event;
	event_f func;
	void *data;
};

static int event_function(void *info)
{
	struct event_function_struct *efs = info;
	struct perf_event *event = efs->event;
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_context *task_ctx = cpuctx->task_ctx;
	int ret = 0;

	lockdep_assert_irqs_disabled();

	perf_ctx_lock(cpuctx, task_ctx);
	/*
	 * Since we do the IPI call without holding ctx->lock things can have
	 * changed, double check we hit the task we set out to hit.
	 */
	if (ctx->task) {
		if (ctx->task != current) {
			ret = -ESRCH;
			goto unlock;
		}

		/*
		 * We only use event_function_call() on established contexts,
		 * and event_function() is only ever called when active (or
		 * rather, we'll have bailed in task_function_call() or the
		 * above ctx->task != current test), therefore we must have
		 * ctx->is_active here.
		 */
		WARN_ON_ONCE(!ctx->is_active);
		/*
		 * And since we have ctx->is_active, cpuctx->task_ctx must
		 * match.
		 */
		WARN_ON_ONCE(task_ctx != ctx);
	} else {
		WARN_ON_ONCE(&cpuctx->ctx != ctx);
	}

	efs->func(event, cpuctx, ctx, efs->data);
unlock:
	perf_ctx_unlock(cpuctx, task_ctx);

	return ret;
}

static void event_function_call(struct perf_event *event, event_f func, void *data)
{
	struct perf_event_context *ctx = event->ctx;
	struct task_struct *task = READ_ONCE(ctx->task); /* verified in event_function */
	struct event_function_struct efs = {
		.event = event,
		.func = func,
		.data = data,
	};

	if (!event->parent) {
		/*
		 * If this is a !child event, we must hold ctx::mutex to
		 * stabilize the event->ctx relation. See
		 * perf_event_ctx_lock().
		 */
		lockdep_assert_held(&ctx->mutex);
	}

	if (!task) {
		cpu_function_call(event->cpu, event_function, &efs);
		return;
	}

	if (task == TASK_TOMBSTONE)
		return;

again:
	if (!task_function_call(task, event_function, &efs))
		return;

	raw_spin_lock_irq(&ctx->lock);
	/*
	 * Reload the task pointer, it might have been changed by
	 * a concurrent perf_event_context_sched_out().
	 */
	task = ctx->task;
	if (task == TASK_TOMBSTONE) {
		raw_spin_unlock_irq(&ctx->lock);
		return;
	}
	if (ctx->is_active) {
		raw_spin_unlock_irq(&ctx->lock);
		goto again;
	}
	func(event, NULL, ctx, data);
	raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Similar to event_function_call() + event_function(), but hard assumes IRQs
 * are already disabled and we're on the right CPU.
 */
static void event_function_local(struct perf_event *event, event_f func, void *data)
{
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct task_struct *task = READ_ONCE(ctx->task);
	struct perf_event_context *task_ctx = NULL;

	lockdep_assert_irqs_disabled();

	if (task) {
		if (task == TASK_TOMBSTONE)
			return;

		task_ctx = ctx;
	}

	perf_ctx_lock(cpuctx, task_ctx);

	task = ctx->task;
	if (task == TASK_TOMBSTONE)
		goto unlock;

	if (task) {
		/*
		 * We must be either inactive or active and the right task,
		 * otherwise we're screwed, since we cannot IPI to somewhere
		 * else.
		 */
		if (ctx->is_active) {
			if (WARN_ON_ONCE(task != current))
				goto unlock;

			if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))
				goto unlock;
		}
	} else {
		WARN_ON_ONCE(&cpuctx->ctx != ctx);
	}

	func(event, cpuctx, ctx, data);
unlock:
	perf_ctx_unlock(cpuctx, task_ctx);
}

#define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
		       PERF_FLAG_FD_OUTPUT  |\
		       PERF_FLAG_PID_CGROUP |\
		       PERF_FLAG_FD_CLOEXEC)

/*
 * branch priv levels that need permission checks
 */
#define PERF_SAMPLE_BRANCH_PERM_PLM \
	(PERF_SAMPLE_BRANCH_KERNEL |\
	 PERF_SAMPLE_BRANCH_HV)

enum event_type_t {
	EVENT_FLEXIBLE = 0x1,
	EVENT_PINNED = 0x2,
	EVENT_TIME = 0x4,
	/* see ctx_resched() for details */
	EVENT_CPU = 0x8,
	EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
};

/*
 * perf_sched_events : >0 events exist
 */

static void perf_sched_delayed(struct work_struct *work);
DEFINE_STATIC_KEY_FALSE(perf_sched_events);
static DECLARE_DELAYED_WORK(perf_sched_work, perf_sched_delayed);
static DEFINE_MUTEX(perf_sched_mutex);
static atomic_t perf_sched_count;

static DEFINE_PER_CPU(struct pmu_event_list, pmu_sb_events);

static atomic_t nr_mmap_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
static atomic_t nr_namespaces_events __read_mostly;
static atomic_t nr_task_events __read_mostly;
static atomic_t nr_freq_events __read_mostly;
static atomic_t nr_switch_events __read_mostly;
static atomic_t nr_ksymbol_events __read_mostly;
static atomic_t nr_bpf_events __read_mostly;
static atomic_t nr_cgroup_events __read_mostly;
static atomic_t nr_text_poke_events __read_mostly;
static atomic_t nr_build_id_events __read_mostly;

static LIST_HEAD(pmus);
static DEFINE_MUTEX(pmus_lock);
static struct srcu_struct pmus_srcu;
static cpumask_var_t perf_online_mask;
static struct kmem_cache *perf_event_cache;

/*
 * perf event paranoia level:
 *  -1 - not paranoid at all
 *   0 - disallow raw tracepoint access for unpriv
 *   1 - disallow cpu events for unpriv
 *   2 - disallow kernel profiling for unpriv
 */
int sysctl_perf_event_paranoid __read_mostly = 2;

/* Minimum for 512 kiB + 1 user control page */
int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */

/*
 * max perf event sample rate
 */
#define DEFAULT_MAX_SAMPLE_RATE		100000
#define DEFAULT_SAMPLE_PERIOD_NS	(NSEC_PER_SEC / DEFAULT_MAX_SAMPLE_RATE)
#define DEFAULT_CPU_TIME_MAX_PERCENT	25

int sysctl_perf_event_sample_rate __read_mostly	= DEFAULT_MAX_SAMPLE_RATE;

static int max_samples_per_tick __read_mostly	= DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
static int perf_sample_period_ns __read_mostly	= DEFAULT_SAMPLE_PERIOD_NS;

static int perf_sample_allowed_ns __read_mostly =
	DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;

static void update_perf_cpu_limits(void)
{
	u64 tmp = perf_sample_period_ns;

	tmp *= sysctl_perf_cpu_time_max_percent;
	tmp = div_u64(tmp, 100);
	if (!tmp)
		tmp = 1;

	WRITE_ONCE(perf_sample_allowed_ns, tmp);
}

static bool perf_rotate_context(struct perf_cpu_pmu_context *cpc);

int perf_proc_update_handler(struct ctl_table *table, int write,
		void *buffer, size_t *lenp, loff_t *ppos)
{
	int ret;
	int perf_cpu = sysctl_perf_cpu_time_max_percent;
	/*
	 * If throttling is disabled don't allow the write:
	 */
	if (write && (perf_cpu == 100 || perf_cpu == 0))
		return -EINVAL;

	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	if (ret || !write)
		return ret;

	max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);
	perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
	update_perf_cpu_limits();

	return 0;
}

int sysctl_perf_cpu_time_max_percent __read_mostly = DEFAULT_CPU_TIME_MAX_PERCENT;

int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
		void *buffer, size_t *lenp, loff_t *ppos)
{
	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);

	if (ret || !write)
		return ret;

	if (sysctl_perf_cpu_time_max_percent == 100 ||
	    sysctl_perf_cpu_time_max_percent == 0) {
		printk(KERN_WARNING
		       "perf: Dynamic interrupt throttling disabled, can hang your system!\n");
		WRITE_ONCE(perf_sample_allowed_ns, 0);
	} else {
		update_perf_cpu_limits();
	}

	return 0;
}

/*
 * perf samples are done in some very critical code paths (NMIs).
 * If they take too much CPU time, the system can lock up and not
 * get any real work done.  This will drop the sample rate when
 * we detect that events are taking too long.
 */
#define NR_ACCUMULATED_SAMPLES 128
static DEFINE_PER_CPU(u64, running_sample_length);

static u64 __report_avg;
static u64 __report_allowed;

static void perf_duration_warn(struct irq_work *w)
{
	printk_ratelimited(KERN_INFO
		"perf: interrupt took too long (%lld > %lld), lowering "
		"kernel.perf_event_max_sample_rate to %d\n",
		__report_avg, __report_allowed,
		sysctl_perf_event_sample_rate);
}

static DEFINE_IRQ_WORK(perf_duration_work, perf_duration_warn);

void perf_sample_event_took(u64 sample_len_ns)
{
	u64 max_len = READ_ONCE(perf_sample_allowed_ns);
	u64 running_len;
	u64 avg_len;
	u32 max;

	if (max_len == 0)
		return;

	/* Decay the counter by 1 average sample. */
	running_len = __this_cpu_read(running_sample_length);
	running_len -= running_len/NR_ACCUMULATED_SAMPLES;
	running_len += sample_len_ns;
	__this_cpu_write(running_sample_length, running_len);

	/*
	 * Note: this will be biased artifically low until we have
	 * seen NR_ACCUMULATED_SAMPLES. Doing it this way keeps us
	 * from having to maintain a count.
	 */
	avg_len = running_len/NR_ACCUMULATED_SAMPLES;
	if (avg_len <= max_len)
		return;

	__report_avg = avg_len;
	__report_allowed = max_len;

	/*
	 * Compute a throttle threshold 25% below the current duration.
	 */
	avg_len += avg_len / 4;
	max = (TICK_NSEC / 100) * sysctl_perf_cpu_time_max_percent;
	if (avg_len < max)
		max /= (u32)avg_len;
	else
		max = 1;

	WRITE_ONCE(perf_sample_allowed_ns, avg_len);
	WRITE_ONCE(max_samples_per_tick, max);

	sysctl_perf_event_sample_rate = max * HZ;
	perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;

	if (!irq_work_queue(&perf_duration_work)) {
		early_printk("perf: interrupt took too long (%lld > %lld), lowering "
			     "kernel.perf_event_max_sample_rate to %d\n",
			     __report_avg, __report_allowed,
			     sysctl_perf_event_sample_rate);
	}
}

static atomic64_t perf_event_id;

static void update_context_time(struct perf_event_context *ctx);
static u64 perf_event_time(struct perf_event *event);

void __weak perf_event_print_debug(void)	{ }

static inline u64 perf_clock(void)
{
	return local_clock();
}

static inline u64 perf_event_clock(struct perf_event *event)
{
	return event->clock();
}

/*
 * State based event timekeeping...
 *
 * The basic idea is to use event->state to determine which (if any) time
 * fields to increment with the current delta. This means we only need to
 * update timestamps when we change state or when they are explicitly requested
 * (read).
 *
 * Event groups make things a little more complicated, but not terribly so. The
 * rules for a group are that if the group leader is OFF the entire group is
 * OFF, irrespecive of what the group member states are. This results in
 * __perf_effective_state().
 *
 * A futher ramification is that when a group leader flips between OFF and
 * !OFF, we need to update all group member times.
 *
 *
 * NOTE: perf_event_time() is based on the (cgroup) context time, and thus we
 * need to make sure the relevant context time is updated before we try and
 * update our timestamps.
 */

static __always_inline enum perf_event_state
__perf_effective_state(struct perf_event *event)
{
	struct perf_event *leader = event->group_leader;

	if (leader->state <= PERF_EVENT_STATE_OFF)
		return leader->state;

	return event->state;
}

static __always_inline void
__perf_update_times(struct perf_event *event, u64 now, u64 *enabled, u64 *running)
{
	enum perf_event_state state = __perf_effective_state(event);
	u64 delta = now - event->tstamp;

	*enabled = event->total_time_enabled;
	if (state >= PERF_EVENT_STATE_INACTIVE)
		*enabled += delta;

	*running = event->total_time_running;
	if (state >= PERF_EVENT_STATE_ACTIVE)
		*running += delta;
}

static void perf_event_update_time(struct perf_event *event)
{
	u64 now = perf_event_time(event);

	__perf_update_times(event, now, &event->total_time_enabled,
					&event->total_time_running);
	event->tstamp = now;
}

static void perf_event_update_sibling_time(struct perf_event *leader)
{
	struct perf_event *sibling;

	for_each_sibling_event(sibling, leader)
		perf_event_update_time(sibling);
}

static void
perf_event_set_state(struct perf_event *event, enum perf_event_state state)
{
	if (event->state == state)
		return;

	perf_event_update_time(event);
	/*
	 * If a group leader gets enabled/disabled all its siblings
	 * are affected too.
	 */
	if ((event->state < 0) ^ (state < 0))
		perf_event_update_sibling_time(event);

	WRITE_ONCE(event->state, state);
}

/*
 * UP store-release, load-acquire
 */

#define __store_release(ptr, val)					\
do {									\
	barrier();							\
	WRITE_ONCE(*(ptr), (val));					\
} while (0)

#define __load_acquire(ptr)						\
({									\
	__unqual_scalar_typeof(*(ptr)) ___p = READ_ONCE(*(ptr));	\
	barrier();							\
	___p;								\
})

static void perf_ctx_disable(struct perf_event_context *ctx)
{
	struct perf_event_pmu_context *pmu_ctx;

	list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry)
		perf_pmu_disable(pmu_ctx->pmu);
}

static void perf_ctx_enable(struct perf_event_context *ctx)
{
	struct perf_event_pmu_context *pmu_ctx;

	list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry)
		perf_pmu_enable(pmu_ctx->pmu);
}

static void ctx_sched_out(struct perf_event_context *ctx, enum event_type_t event_type);
static void ctx_sched_in(struct perf_event_context *ctx, enum event_type_t event_type);

#ifdef CONFIG_CGROUP_PERF

static inline bool
perf_cgroup_match(struct perf_event *event)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);

	/* @event doesn't care about cgroup */
	if (!event->cgrp)
		return true;

	/* wants specific cgroup scope but @cpuctx isn't associated with any */
	if (!cpuctx->cgrp)
		return false;

	/*
	 * Cgroup scoping is recursive.  An event enabled for a cgroup is
	 * also enabled for all its descendant cgroups.  If @cpuctx's
	 * cgroup is a descendant of @event's (the test covers identity
	 * case), it's a match.
	 */
	return cgroup_is_descendant(cpuctx->cgrp->css.cgroup,
				    event->cgrp->css.cgroup);
}

static inline void perf_detach_cgroup(struct perf_event *event)
{
	css_put(&event->cgrp->css);
	event->cgrp = NULL;
}

static inline int is_cgroup_event(struct perf_event *event)
{
	return event->cgrp != NULL;
}

static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
	struct perf_cgroup_info *t;

	t = per_cpu_ptr(event->cgrp->info, event->cpu);
	return t->time;
}

static inline u64 perf_cgroup_event_time_now(struct perf_event *event, u64 now)
{
	struct perf_cgroup_info *t;

	t = per_cpu_ptr(event->cgrp->info, event->cpu);
	if (!__load_acquire(&t->active))
		return t->time;
	now += READ_ONCE(t->timeoffset);
	return now;
}

static inline void __update_cgrp_time(struct perf_cgroup_info *info, u64 now, bool adv)
{
	if (adv)
		info->time += now - info->timestamp;
	info->timestamp = now;
	/*
	 * see update_context_time()
	 */
	WRITE_ONCE(info->timeoffset, info->time - info->timestamp);
}

static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx, bool final)
{
	struct perf_cgroup *cgrp = cpuctx->cgrp;
	struct cgroup_subsys_state *css;
	struct perf_cgroup_info *info;

	if (cgrp) {
		u64 now = perf_clock();

		for (css = &cgrp->css; css; css = css->parent) {
			cgrp = container_of(css, struct perf_cgroup, css);
			info = this_cpu_ptr(cgrp->info);

			__update_cgrp_time(info, now, true);
			if (final)
				__store_release(&info->active, 0);
		}
	}
}

static inline void update_cgrp_time_from_event(struct perf_event *event)
{
	struct perf_cgroup_info *info;

	/*
	 * ensure we access cgroup data only when needed and
	 * when we know the cgroup is pinned (css_get)
	 */
	if (!is_cgroup_event(event))
		return;

	info = this_cpu_ptr(event->cgrp->info);
	/*
	 * Do not update time when cgroup is not active
	 */
	if (info->active)
		__update_cgrp_time(info, perf_clock(), true);
}

static inline void
perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx)
{
	struct perf_event_context *ctx = &cpuctx->ctx;
	struct perf_cgroup *cgrp = cpuctx->cgrp;
	struct perf_cgroup_info *info;
	struct cgroup_subsys_state *css;

	/*
	 * ctx->lock held by caller
	 * ensure we do not access cgroup data
	 * unless we have the cgroup pinned (css_get)
	 */
	if (!cgrp)
		return;

	WARN_ON_ONCE(!ctx->nr_cgroups);

	for (css = &cgrp->css; css; css = css->parent) {
		cgrp = container_of(css, struct perf_cgroup, css);
		info = this_cpu_ptr(cgrp->info);
		__update_cgrp_time(info, ctx->timestamp, false);
		__store_release(&info->active, 1);
	}
}

/*
 * reschedule events based on the cgroup constraint of task.
 */
static void perf_cgroup_switch(struct task_struct *task)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_cgroup *cgrp;

	/*
	 * cpuctx->cgrp is set when the first cgroup event enabled,
	 * and is cleared when the last cgroup event disabled.
	 */
	if (READ_ONCE(cpuctx->cgrp) == NULL)
		return;

	WARN_ON_ONCE(cpuctx->ctx.nr_cgroups == 0);

	cgrp = perf_cgroup_from_task(task, NULL);
	if (READ_ONCE(cpuctx->cgrp) == cgrp)
		return;

	perf_ctx_lock(cpuctx, cpuctx->task_ctx);
	perf_ctx_disable(&cpuctx->ctx);

	ctx_sched_out(&cpuctx->ctx, EVENT_ALL);
	/*
	 * must not be done before ctxswout due
	 * to update_cgrp_time_from_cpuctx() in
	 * ctx_sched_out()
	 */
	cpuctx->cgrp = cgrp;
	/*
	 * set cgrp before ctxsw in to allow
	 * perf_cgroup_set_timestamp() in ctx_sched_in()
	 * to not have to pass task around
	 */
	ctx_sched_in(&cpuctx->ctx, EVENT_ALL);

	perf_ctx_enable(&cpuctx->ctx);
	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
}

static int perf_cgroup_ensure_storage(struct perf_event *event,
				struct cgroup_subsys_state *css)
{
	struct perf_cpu_context *cpuctx;
	struct perf_event **storage;
	int cpu, heap_size, ret = 0;

	/*
	 * Allow storage to have sufficent space for an iterator for each
	 * possibly nested cgroup plus an iterator for events with no cgroup.
	 */
	for (heap_size = 1; css; css = css->parent)
		heap_size++;

	for_each_possible_cpu(cpu) {
		cpuctx = per_cpu_ptr(&perf_cpu_context, cpu);
		if (heap_size <= cpuctx->heap_size)
			continue;

		storage = kmalloc_node(heap_size * sizeof(struct perf_event *),
				       GFP_KERNEL, cpu_to_node(cpu));
		if (!storage) {
			ret = -ENOMEM;
			break;
		}

		raw_spin_lock_irq(&cpuctx->ctx.lock);
		if (cpuctx->heap_size < heap_size) {
			swap(cpuctx->heap, storage);
			if (storage == cpuctx->heap_default)
				storage = NULL;
			cpuctx->heap_size = heap_size;
		}
		raw_spin_unlock_irq(&cpuctx->ctx.lock);

		kfree(storage);
	}

	return ret;
}

static inline int perf_cgroup_connect(int fd, struct perf_event *event,
				      struct perf_event_attr *attr,
				      struct perf_event *group_leader)
{
	struct perf_cgroup *cgrp;
	struct cgroup_subsys_state *css;
	struct fd f = fdget(fd);
	int ret = 0;

	if (!f.file)
		return -EBADF;

	css = css_tryget_online_from_dir(f.file->f_path.dentry,
					 &perf_event_cgrp_subsys);
	if (IS_ERR(css)) {
		ret = PTR_ERR(css);
		goto out;
	}

	ret = perf_cgroup_ensure_storage(event, css);
	if (ret)
		goto out;

	cgrp = container_of(css, struct perf_cgroup, css);
	event->cgrp = cgrp;

	/*
	 * all events in a group must monitor
	 * the same cgroup because a task belongs
	 * to only one perf cgroup at a time
	 */
	if (group_leader && group_leader->cgrp != cgrp) {
		perf_detach_cgroup(event);
		ret = -EINVAL;
	}
out:
	fdput(f);
	return ret;
}

static inline void
perf_cgroup_event_enable(struct perf_event *event, struct perf_event_context *ctx)
{
	struct perf_cpu_context *cpuctx;

	if (!is_cgroup_event(event))
		return;

	/*
	 * Because cgroup events are always per-cpu events,
	 * @ctx == &cpuctx->ctx.
	 */
	cpuctx = container_of(ctx, struct perf_cpu_context, ctx);

	if (ctx->nr_cgroups++)
		return;

	cpuctx->cgrp = perf_cgroup_from_task(current, ctx);
}

static inline void
perf_cgroup_event_disable(struct perf_event *event, struct perf_event_context *ctx)
{
	struct perf_cpu_context *cpuctx;

	if (!is_cgroup_event(event))
		return;

	/*
	 * Because cgroup events are always per-cpu events,
	 * @ctx == &cpuctx->ctx.
	 */
	cpuctx = container_of(ctx, struct perf_cpu_context, ctx);

	if (--ctx->nr_cgroups)
		return;

	cpuctx->cgrp = NULL;
}

#else /* !CONFIG_CGROUP_PERF */

static inline bool
perf_cgroup_match(struct perf_event *event)
{
	return true;
}

static inline void perf_detach_cgroup(struct perf_event *event)
{}

static inline int is_cgroup_event(struct perf_event *event)
{
	return 0;
}

static inline void update_cgrp_time_from_event(struct perf_event *event)
{
}

static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx,
						bool final)
{
}

static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event,
				      struct perf_event_attr *attr,
				      struct perf_event *group_leader)
{
	return -EINVAL;
}

static inline void
perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx)
{
}

static inline u64 perf_cgroup_event_time(struct perf_event *event)
{
	return 0;
}

static inline u64 perf_cgroup_event_time_now(struct perf_event *event, u64 now)
{
	return 0;
}

static inline void
perf_cgroup_event_enable(struct perf_event *event, struct perf_event_context *ctx)
{
}

static inline void
perf_cgroup_event_disable(struct perf_event *event, struct perf_event_context *ctx)
{
}

static void perf_cgroup_switch(struct task_struct *task)
{
}
#endif

/*
 * set default to be dependent on timer tick just
 * like original code
 */
#define PERF_CPU_HRTIMER (1000 / HZ)
/*
 * function must be called with interrupts disabled
 */
static enum hrtimer_restart perf_mux_hrtimer_handler(struct hrtimer *hr)
{
	struct perf_cpu_pmu_context *cpc;
	bool rotations;

	lockdep_assert_irqs_disabled();

	cpc = container_of(hr, struct perf_cpu_pmu_context, hrtimer);
	rotations = perf_rotate_context(cpc);

	raw_spin_lock(&cpc->hrtimer_lock);
	if (rotations)
		hrtimer_forward_now(hr, cpc->hrtimer_interval);
	else
		cpc->hrtimer_active = 0;
	raw_spin_unlock(&cpc->hrtimer_lock);

	return rotations ? HRTIMER_RESTART : HRTIMER_NORESTART;
}

static void __perf_mux_hrtimer_init(struct perf_cpu_pmu_context *cpc, int cpu)
{
	struct hrtimer *timer = &cpc->hrtimer;
	struct pmu *pmu = cpc->epc.pmu;
	u64 interval;

	/*
	 * check default is sane, if not set then force to
	 * default interval (1/tick)
	 */
	interval = pmu->hrtimer_interval_ms;
	if (interval < 1)
		interval = pmu->hrtimer_interval_ms = PERF_CPU_HRTIMER;

	cpc->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * interval);

	raw_spin_lock_init(&cpc->hrtimer_lock);
	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
	timer->function = perf_mux_hrtimer_handler;
}

static int perf_mux_hrtimer_restart(struct perf_cpu_pmu_context *cpc)
{
	struct hrtimer *timer = &cpc->hrtimer;
	unsigned long flags;

	raw_spin_lock_irqsave(&cpc->hrtimer_lock, flags);
	if (!cpc->hrtimer_active) {
		cpc->hrtimer_active = 1;
		hrtimer_forward_now(timer, cpc->hrtimer_interval);
		hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED_HARD);
	}
	raw_spin_unlock_irqrestore(&cpc->hrtimer_lock, flags);

	return 0;
}

static int perf_mux_hrtimer_restart_ipi(void *arg)
{
	return perf_mux_hrtimer_restart(arg);
}

void perf_pmu_disable(struct pmu *pmu)
{
	int *count = this_cpu_ptr(pmu->pmu_disable_count);
	if (!(*count)++)
		pmu->pmu_disable(pmu);
}

void perf_pmu_enable(struct pmu *pmu)
{
	int *count = this_cpu_ptr(pmu->pmu_disable_count);
	if (!--(*count))
		pmu->pmu_enable(pmu);
}

static void perf_assert_pmu_disabled(struct pmu *pmu)
{
	WARN_ON_ONCE(*this_cpu_ptr(pmu->pmu_disable_count) == 0);
}

static void get_ctx(struct perf_event_context *ctx)
{
	refcount_inc(&ctx->refcount);
}

static void *alloc_task_ctx_data(struct pmu *pmu)
{
	if (pmu->task_ctx_cache)
		return kmem_cache_zalloc(pmu->task_ctx_cache, GFP_KERNEL);

	return NULL;
}

static void free_task_ctx_data(struct pmu *pmu, void *task_ctx_data)
{
	if (pmu->task_ctx_cache && task_ctx_data)
		kmem_cache_free(pmu->task_ctx_cache, task_ctx_data);
}

static void free_ctx(struct rcu_head *head)
{
	struct perf_event_context *ctx;

	ctx = container_of(head, struct perf_event_context, rcu_head);
	kfree(ctx);
}

static void put_ctx(struct perf_event_context *ctx)
{
	if (refcount_dec_and_test(&ctx->refcount)) {
		if (ctx->parent_ctx)
			put_ctx(ctx->parent_ctx);
		if (ctx->task && ctx->task != TASK_TOMBSTONE)
			put_task_struct(ctx->task);
		call_rcu(&ctx->rcu_head, free_ctx);
	}
}

/*
 * Because of perf_event::ctx migration in sys_perf_event_open::move_group and
 * perf_pmu_migrate_context() we need some magic.
 *
 * Those places that change perf_event::ctx will hold both
 * perf_event_ctx::mutex of the 'old' and 'new' ctx value.
 *
 * Lock ordering is by mutex address. There are two other sites where
 * perf_event_context::mutex nests and those are:
 *
 *  - perf_event_exit_task_context()	[ child , 0 ]
 *      perf_event_exit_event()
 *        put_event()			[ parent, 1 ]
 *
 *  - perf_event_init_context()		[ parent, 0 ]
 *      inherit_task_group()
 *        inherit_group()
 *          inherit_event()
 *            perf_event_alloc()
 *              perf_init_event()
 *                perf_try_init_event()	[ child , 1 ]
 *
 * While it appears there is an obvious deadlock here -- the parent and child
 * nesting levels are inverted between the two. This is in fact safe because
 * life-time rules separate them. That is an exiting task cannot fork, and a
 * spawning task cannot (yet) exit.
 *
 * But remember that these are parent<->child context relations, and
 * migration does not affect children, therefore these two orderings should not
 * interact.
 *
 * The change in perf_event::ctx does not affect children (as claimed above)
 * because the sys_perf_event_open() case will install a new event and break
 * the ctx parent<->child relation, and perf_pmu_migrate_context() is only
 * concerned with cpuctx and that doesn't have children.
 *
 * The places that change perf_event::ctx will issue:
 *
 *   perf_remove_from_context();
 *   synchronize_rcu();
 *   perf_install_in_context();
 *
 * to affect the change. The remove_from_context() + synchronize_rcu() should
 * quiesce the event, after which we can install it in the new location. This
 * means that only external vectors (perf_fops, prctl) can perturb the event
 * while in transit. Therefore all such accessors should also acquire
 * perf_event_context::mutex to serialize against this.
 *
 * However; because event->ctx can change while we're waiting to acquire
 * ctx->mutex we must be careful and use the below perf_event_ctx_lock()
 * function.
 *
 * Lock order:
 *    exec_update_lock
 *	task_struct::perf_event_mutex
 *	  perf_event_context::mutex
 *	    perf_event::child_mutex;
 *	      perf_event_context::lock
 *	    perf_event::mmap_mutex
 *	    mmap_lock
 *	      perf_addr_filters_head::lock
 *
 *    cpu_hotplug_lock
 *      pmus_lock
 *	  cpuctx->mutex / perf_event_context::mutex
 */
static struct perf_event_context *
perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
{
	struct perf_event_context *ctx;

again:
	rcu_read_lock();
	ctx = READ_ONCE(event->ctx);
	if (!refcount_inc_not_zero(&ctx->refcount)) {
		rcu_read_unlock();
		goto again;
	}
	rcu_read_unlock();

	mutex_lock_nested(&ctx->mutex, nesting);
	if (event->ctx != ctx) {
		mutex_unlock(&ctx->mutex);
		put_ctx(ctx);
		goto again;
	}

	return ctx;
}

static inline struct perf_event_context *
perf_event_ctx_lock(struct perf_event *event)
{
	return perf_event_ctx_lock_nested(event, 0);
}

static void perf_event_ctx_unlock(struct perf_event *event,
				  struct perf_event_context *ctx)
{
	mutex_unlock(&ctx->mutex);
	put_ctx(ctx);
}

/*
 * This must be done under the ctx->lock, such as to serialize against
 * context_equiv(), therefore we cannot call put_ctx() since that might end up
 * calling scheduler related locks and ctx->lock nests inside those.
 */
static __must_check struct perf_event_context *
unclone_ctx(struct perf_event_context *ctx)
{
	struct perf_event_context *parent_ctx = ctx->parent_ctx;

	lockdep_assert_held(&ctx->lock);

	if (parent_ctx)
		ctx->parent_ctx = NULL;
	ctx->generation++;

	return parent_ctx;
}

static u32 perf_event_pid_type(struct perf_event *event, struct task_struct *p,
				enum pid_type type)
{
	u32 nr;
	/*
	 * only top level events have the pid namespace they were created in
	 */
	if (event->parent)
		event = event->parent;

	nr = __task_pid_nr_ns(p, type, event->ns);
	/* avoid -1 if it is idle thread or runs in another ns */
	if (!nr && !pid_alive(p))
		nr = -1;
	return nr;
}

static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
{
	return perf_event_pid_type(event, p, PIDTYPE_TGID);
}

static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
{
	return perf_event_pid_type(event, p, PIDTYPE_PID);
}

/*
 * If we inherit events we want to return the parent event id
 * to userspace.
 */
static u64 primary_event_id(struct perf_event *event)
{
	u64 id = event->id;

	if (event->parent)
		id = event->parent->id;

	return id;
}

/*
 * Get the perf_event_context for a task and lock it.
 *
 * This has to cope with the fact that until it is locked,
 * the context could get moved to another task.
 */
static struct perf_event_context *
perf_lock_task_context(struct task_struct *task, unsigned long *flags)
{
	struct perf_event_context *ctx;

retry:
	/*
	 * One of the few rules of preemptible RCU is that one cannot do
	 * rcu_read_unlock() while holding a scheduler (or nested) lock when
	 * part of the read side critical section was irqs-enabled -- see
	 * rcu_read_unlock_special().
	 *
	 * Since ctx->lock nests under rq->lock we must ensure the entire read
	 * side critical section has interrupts disabled.
	 */
	local_irq_save(*flags);
	rcu_read_lock();
	ctx = rcu_dereference(task->perf_event_ctxp);
	if (ctx) {
		/*
		 * If this context is a clone of another, it might
		 * get swapped for another underneath us by
		 * perf_event_task_sched_out, though the
		 * rcu_read_lock() protects us from any context
		 * getting freed.  Lock the context and check if it
		 * got swapped before we could get the lock, and retry
		 * if so.  If we locked the right context, then it
		 * can't get swapped on us any more.
		 */
		raw_spin_lock(&ctx->lock);
		if (ctx != rcu_dereference(task->perf_event_ctxp)) {
			raw_spin_unlock(&ctx->lock);
			rcu_read_unlock();
			local_irq_restore(*flags);
			goto retry;
		}

		if (ctx->task == TASK_TOMBSTONE ||
		    !refcount_inc_not_zero(&ctx->refcount)) {
			raw_spin_unlock(&ctx->lock);
			ctx = NULL;
		} else {
			WARN_ON_ONCE(ctx->task != task);
		}
	}
	rcu_read_unlock();
	if (!ctx)
		local_irq_restore(*flags);
	return ctx;
}

/*
 * Get the context for a task and increment its pin_count so it
 * can't get swapped to another task.  This also increments its
 * reference count so that the context can't get freed.
 */
static struct perf_event_context *
perf_pin_task_context(struct task_struct *task)
{
	struct perf_event_context *ctx;
	unsigned long flags;

	ctx = perf_lock_task_context(task, &flags);
	if (ctx) {
		++ctx->pin_count;
		raw_spin_unlock_irqrestore(&ctx->lock, flags);
	}
	return ctx;
}

static void perf_unpin_context(struct perf_event_context *ctx)
{
	unsigned long flags;

	raw_spin_lock_irqsave(&ctx->lock, flags);
	--ctx->pin_count;
	raw_spin_unlock_irqrestore(&ctx->lock, flags);
}

/*
 * Update the record of the current time in a context.
 */
static void __update_context_time(struct perf_event_context *ctx, bool adv)
{
	u64 now = perf_clock();

	lockdep_assert_held(&ctx->lock);

	if (adv)
		ctx->time += now - ctx->timestamp;
	ctx->timestamp = now;

	/*
	 * The above: time' = time + (now - timestamp), can be re-arranged
	 * into: time` = now + (time - timestamp), which gives a single value
	 * offset to compute future time without locks on.
	 *
	 * See perf_event_time_now(), which can be used from NMI context where
	 * it's (obviously) not possible to acquire ctx->lock in order to read
	 * both the above values in a consistent manner.
	 */
	WRITE_ONCE(ctx->timeoffset, ctx->time - ctx->timestamp);
}

static void update_context_time(struct perf_event_context *ctx)
{
	__update_context_time(ctx, true);
}

static u64 perf_event_time(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;

	if (unlikely(!ctx))
		return 0;

	if (is_cgroup_event(event))
		return perf_cgroup_event_time(event);

	return ctx->time;
}

static u64 perf_event_time_now(struct perf_event *event, u64 now)
{
	struct perf_event_context *ctx = event->ctx;

	if (unlikely(!ctx))
		return 0;

	if (is_cgroup_event(event))
		return perf_cgroup_event_time_now(event, now);

	if (!(__load_acquire(&ctx->is_active) & EVENT_TIME))
		return ctx->time;

	now += READ_ONCE(ctx->timeoffset);
	return now;
}

static enum event_type_t get_event_type(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;
	enum event_type_t event_type;

	lockdep_assert_held(&ctx->lock);

	/*
	 * It's 'group type', really, because if our group leader is
	 * pinned, so are we.
	 */
	if (event->group_leader != event)
		event = event->group_leader;

	event_type = event->attr.pinned ? EVENT_PINNED : EVENT_FLEXIBLE;
	if (!ctx->task)
		event_type |= EVENT_CPU;

	return event_type;
}

/*
 * Helper function to initialize event group nodes.
 */
static void init_event_group(struct perf_event *event)
{
	RB_CLEAR_NODE(&event->group_node);
	event->group_index = 0;
}

/*
 * Extract pinned or flexible groups from the context
 * based on event attrs bits.
 */
static struct perf_event_groups *
get_event_groups(struct perf_event *event, struct perf_event_context *ctx)
{
	if (event->attr.pinned)
		return &ctx->pinned_groups;
	else
		return &ctx->flexible_groups;
}

/*
 * Helper function to initializes perf_event_group trees.
 */
static void perf_event_groups_init(struct perf_event_groups *groups)
{
	groups->tree = RB_ROOT;
	groups->index = 0;
}

static inline struct cgroup *event_cgroup(const struct perf_event *event)
{
	struct cgroup *cgroup = NULL;

#ifdef CONFIG_CGROUP_PERF
	if (event->cgrp)
		cgroup = event->cgrp->css.cgroup;
#endif

	return cgroup;
}

/*
 * Compare function for event groups;
 *
 * Implements complex key that first sorts by CPU and then by virtual index
 * which provides ordering when rotating groups for the same CPU.
 */
static __always_inline int
perf_event_groups_cmp(const int left_cpu, const struct pmu *left_pmu,
		      const struct cgroup *left_cgroup, const u64 left_group_index,
		      const struct perf_event *right)
{
	if (left_cpu < right->cpu)
		return -1;
	if (left_cpu > right->cpu)
		return 1;

	if (left_pmu) {
		if (left_pmu < right->pmu_ctx->pmu)
			return -1;
		if (left_pmu > right->pmu_ctx->pmu)
			return 1;
	}

#ifdef CONFIG_CGROUP_PERF
	{
		const struct cgroup *right_cgroup = event_cgroup(right);

		if (left_cgroup != right_cgroup) {
			if (!left_cgroup) {
				/*
				 * Left has no cgroup but right does, no
				 * cgroups come first.
				 */
				return -1;
			}
			if (!right_cgroup) {
				/*
				 * Right has no cgroup but left does, no
				 * cgroups come first.
				 */
				return 1;
			}
			/* Two dissimilar cgroups, order by id. */
			if (cgroup_id(left_cgroup) < cgroup_id(right_cgroup))
				return -1;

			return 1;
		}
	}
#endif

	if (left_group_index < right->group_index)
		return -1;
	if (left_group_index > right->group_index)
		return 1;

	return 0;
}

#define __node_2_pe(node) \
	rb_entry((node), struct perf_event, group_node)

static inline bool __group_less(struct rb_node *a, const struct rb_node *b)
{
	struct perf_event *e = __node_2_pe(a);
	return perf_event_groups_cmp(e->cpu, e->pmu_ctx->pmu, event_cgroup(e),
				     e->group_index, __node_2_pe(b)) < 0;
}

struct __group_key {
	int cpu;
	struct pmu *pmu;
	struct cgroup *cgroup;
};

static inline int __group_cmp(const void *key, const struct rb_node *node)
{
	const struct __group_key *a = key;
	const struct perf_event *b = __node_2_pe(node);

	/* partial/subtree match: @cpu, @pmu, @cgroup; ignore: @group_index */
	return perf_event_groups_cmp(a->cpu, a->pmu, a->cgroup, b->group_index, b);
}

static inline int
__group_cmp_ignore_cgroup(const void *key, const struct rb_node *node)
{
	const struct __group_key *a = key;
	const struct perf_event *b = __node_2_pe(node);

	/* partial/subtree match: @cpu, @pmu, ignore: @cgroup, @group_index */
	return perf_event_groups_cmp(a->cpu, a->pmu, event_cgroup(b),
				     b->group_index, b);
}

/*
 * Insert @event into @groups' tree; using
 *   {@event->cpu, @event->pmu_ctx->pmu, event_cgroup(@event), ++@groups->index}
 * as key. This places it last inside the {cpu,pmu,cgroup} subtree.
 */
static void
perf_event_groups_insert(struct perf_event_groups *groups,
			 struct perf_event *event)
{
	event->group_index = ++groups->index;

	rb_add(&event->group_node, &groups->tree, __group_less);
}

/*
 * Helper function to insert event into the pinned or flexible groups.
 */
static void
add_event_to_groups(struct perf_event *event, struct perf_event_context *ctx)
{
	struct perf_event_groups *groups;

	groups = get_event_groups(event, ctx);
	perf_event_groups_insert(groups, event);
}

/*
 * Delete a group from a tree.
 */
static void
perf_event_groups_delete(struct perf_event_groups *groups,
			 struct perf_event *event)
{
	WARN_ON_ONCE(RB_EMPTY_NODE(&event->group_node) ||
		     RB_EMPTY_ROOT(&groups->tree));

	rb_erase(&event->group_node, &groups->tree);
	init_event_group(event);
}

/*
 * Helper function to delete event from its groups.
 */
static void
del_event_from_groups(struct perf_event *event, struct perf_event_context *ctx)
{
	struct perf_event_groups *groups;

	groups = get_event_groups(event, ctx);
	perf_event_groups_delete(groups, event);
}

/*
 * Get the leftmost event in the {cpu,pmu,cgroup} subtree.
 */
static struct perf_event *
perf_event_groups_first(struct perf_event_groups *groups, int cpu,
			struct pmu *pmu, struct cgroup *cgrp)
{
	struct __group_key key = {
		.cpu = cpu,
		.pmu = pmu,
		.cgroup = cgrp,
	};
	struct rb_node *node;

	node = rb_find_first(&key, &groups->tree, __group_cmp);
	if (node)
		return __node_2_pe(node);

	return NULL;
}

static struct perf_event *
perf_event_groups_next(struct perf_event *event, struct pmu *pmu)
{
	struct __group_key key = {
		.cpu = event->cpu,
		.pmu = pmu,
		.cgroup = event_cgroup(event),
	};
	struct rb_node *next;

	next = rb_next_match(&key, &event->group_node, __group_cmp);
	if (next)
		return __node_2_pe(next);

	return NULL;
}

#define perf_event_groups_for_cpu_pmu(event, groups, cpu, pmu)		\
	for (event = perf_event_groups_first(groups, cpu, pmu, NULL);	\
	     event; event = perf_event_groups_next(event, pmu))

/*
 * Iterate through the whole groups tree.
 */
#define perf_event_groups_for_each(event, groups)			\
	for (event = rb_entry_safe(rb_first(&((groups)->tree)),		\
				typeof(*event), group_node); event;	\
		event = rb_entry_safe(rb_next(&event->group_node),	\
				typeof(*event), group_node))

/*
 * Add an event from the lists for its context.
 * Must be called with ctx->mutex and ctx->lock held.
 */
static void
list_add_event(struct perf_event *event, struct perf_event_context *ctx)
{
	lockdep_assert_held(&ctx->lock);

	WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
	event->attach_state |= PERF_ATTACH_CONTEXT;

	event->tstamp = perf_event_time(event);

	/*
	 * If we're a stand alone event or group leader, we go to the context
	 * list, group events are kept attached to the group so that
	 * perf_group_detach can, at all times, locate all siblings.
	 */
	if (event->group_leader == event) {
		event->group_caps = event->event_caps;
		add_event_to_groups(event, ctx);
	}

	list_add_rcu(&event->event_entry, &ctx->event_list);
	ctx->nr_events++;
	if (event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT)
		ctx->nr_user++;
	if (event->attr.inherit_stat)
		ctx->nr_stat++;

	if (event->state > PERF_EVENT_STATE_OFF)
		perf_cgroup_event_enable(event, ctx);

	ctx->generation++;
	event->pmu_ctx->nr_events++;
}

/*
 * Initialize event state based on the perf_event_attr::disabled.
 */
static inline void perf_event__state_init(struct perf_event *event)
{
	event->state = event->attr.disabled ? PERF_EVENT_STATE_OFF :
					      PERF_EVENT_STATE_INACTIVE;
}

static void __perf_event_read_size(struct perf_event *event, int nr_siblings)
{
	int entry = sizeof(u64); /* value */
	int size = 0;
	int nr = 1;

	if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
		size += sizeof(u64);

	if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
		size += sizeof(u64);

	if (event->attr.read_format & PERF_FORMAT_ID)
		entry += sizeof(u64);

	if (event->attr.read_format & PERF_FORMAT_LOST)
		entry += sizeof(u64);

	if (event->attr.read_format & PERF_FORMAT_GROUP) {
		nr += nr_siblings;
		size += sizeof(u64);
	}

	size += entry * nr;
	event->read_size = size;
}

static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
{
	struct perf_sample_data *data;
	u16 size = 0;

	if (sample_type & PERF_SAMPLE_IP)
		size += sizeof(data->ip);

	if (sample_type & PERF_SAMPLE_ADDR)
		size += sizeof(data->addr);

	if (sample_type & PERF_SAMPLE_PERIOD)
		size += sizeof(data->period);

	if (sample_type & PERF_SAMPLE_WEIGHT_TYPE)
		size += sizeof(data->weight.full);

	if (sample_type & PERF_SAMPLE_READ)
		size += event->read_size;

	if (sample_type & PERF_SAMPLE_DATA_SRC)
		size += sizeof(data->data_src.val);

	if (sample_type & PERF_SAMPLE_TRANSACTION)
		size += sizeof(data->txn);

	if (sample_type & PERF_SAMPLE_PHYS_ADDR)
		size += sizeof(data->phys_addr);

	if (sample_type & PERF_SAMPLE_CGROUP)
		size += sizeof(data->cgroup);

	if (sample_type & PERF_SAMPLE_DATA_PAGE_SIZE)
		size += sizeof(data->data_page_size);

	if (sample_type & PERF_SAMPLE_CODE_PAGE_SIZE)
		size += sizeof(data->code_page_size);

	event->header_size = size;
}

/*
 * Called at perf_event creation and when events are attached/detached from a
 * group.
 */
static void perf_event__header_size(struct perf_event *event)
{
	__perf_event_read_size(event,
			       event->group_leader->nr_siblings);
	__perf_event_header_size(event, event->attr.sample_type);
}

static void perf_event__id_header_size(struct perf_event *event)
{
	struct perf_sample_data *data;
	u64 sample_type = event->attr.sample_type;
	u16 size = 0;

	if (sample_type & PERF_SAMPLE_TID)
		size += sizeof(data->tid_entry);

	if (sample_type & PERF_SAMPLE_TIME)
		size += sizeof(data->time);

	if (sample_type & PERF_SAMPLE_IDENTIFIER)
		size += sizeof(data->id);

	if (sample_type & PERF_SAMPLE_ID)
		size += sizeof(data->id);

	if (sample_type & PERF_SAMPLE_STREAM_ID)
		size += sizeof(data->stream_id);

	if (sample_type & PERF_SAMPLE_CPU)
		size += sizeof(data->cpu_entry);

	event->id_header_size = size;
}

static bool perf_event_validate_size(struct perf_event *event)
{
	/*
	 * The values computed here will be over-written when we actually
	 * attach the event.
	 */
	__perf_event_read_size(event, event->group_leader->nr_siblings + 1);
	__perf_event_header_size(event, event->attr.sample_type & ~PERF_SAMPLE_READ);
	perf_event__id_header_size(event);

	/*
	 * Sum the lot; should not exceed the 64k limit we have on records.
	 * Conservative limit to allow for callchains and other variable fields.
	 */
	if (event->read_size + event->header_size +
	    event->id_header_size + sizeof(struct perf_event_header) >= 16*1024)
		return false;

	return true;
}

static void perf_group_attach(struct perf_event *event)
{
	struct perf_event *group_leader = event->group_leader, *pos;

	lockdep_assert_held(&event->ctx->lock);

	/*
	 * We can have double attach due to group movement (move_group) in
	 * perf_event_open().
	 */
	if (event->attach_state & PERF_ATTACH_GROUP)
		return;

	event->attach_state |= PERF_ATTACH_GROUP;

	if (group_leader == event)
		return;

	WARN_ON_ONCE(group_leader->ctx != event->ctx);

	group_leader->group_caps &= event->event_caps;

	list_add_tail(&event->sibling_list, &group_leader->sibling_list);
	group_leader->nr_siblings++;

	perf_event__header_size(group_leader);

	for_each_sibling_event(pos, group_leader)
		perf_event__header_size(pos);
}

/*
 * Remove an event from the lists for its context.
 * Must be called with ctx->mutex and ctx->lock held.
 */
static void
list_del_event(struct perf_event *event, struct perf_event_context *ctx)
{
	WARN_ON_ONCE(event->ctx != ctx);
	lockdep_assert_held(&ctx->lock);

	/*
	 * We can have double detach due to exit/hot-unplug + close.
	 */
	if (!(event->attach_state & PERF_ATTACH_CONTEXT))
		return;

	event->attach_state &= ~PERF_ATTACH_CONTEXT;

	ctx->nr_events--;
	if (event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT)
		ctx->nr_user--;
	if (event->attr.inherit_stat)
		ctx->nr_stat--;

	list_del_rcu(&event->event_entry);

	if (event->group_leader == event)
		del_event_from_groups(event, ctx);

	/*
	 * If event was in error state, then keep it
	 * that way, otherwise bogus counts will be
	 * returned on read(). The only way to get out
	 * of error state is by explicit re-enabling
	 * of the event
	 */
	if (event->state > PERF_EVENT_STATE_OFF) {
		perf_cgroup_event_disable(event, ctx);
		perf_event_set_state(event, PERF_EVENT_STATE_OFF);
	}

	ctx->generation++;
	event->pmu_ctx->nr_events--;
}

static int
perf_aux_output_match(struct perf_event *event, struct perf_event *aux_event)
{
	if (!has_aux(aux_event))
		return 0;

	if (!event->pmu->aux_output_match)
		return 0;

	return event->pmu->aux_output_match(aux_event);
}

static void put_event(struct perf_event *event);
static void event_sched_out(struct perf_event *event,
			    struct perf_event_context *ctx);

static void perf_put_aux_event(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;
	struct perf_event *iter;

	/*
	 * If event uses aux_event tear down the link
	 */
	if (event->aux_event) {
		iter = event->aux_event;
		event->aux_event = NULL;
		put_event(iter);
		return;
	}

	/*
	 * If the event is an aux_event, tear down all links to
	 * it from other events.
	 */
	for_each_sibling_event(iter, event->group_leader) {
		if (iter->aux_event != event)
			continue;

		iter->aux_event = NULL;
		put_event(event);

		/*
		 * If it's ACTIVE, schedule it out and put it into ERROR
		 * state so that we don't try to schedule it again. Note
		 * that perf_event_enable() will clear the ERROR status.
		 */
		event_sched_out(iter, ctx);
		perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
	}
}

static bool perf_need_aux_event(struct perf_event *event)
{
	return !!event->attr.aux_output || !!event->attr.aux_sample_size;
}

static int perf_get_aux_event(struct perf_event *event,
			      struct perf_event *group_leader)
{
	/*
	 * Our group leader must be an aux event if we want to be
	 * an aux_output. This way, the aux event will precede its
	 * aux_output events in the group, and therefore will always
	 * schedule first.
	 */
	if (!group_leader)
		return 0;

	/*
	 * aux_output and aux_sample_size are mutually exclusive.
	 */
	if (event->attr.aux_output && event->attr.aux_sample_size)
		return 0;

	if (event->attr.aux_output &&
	    !perf_aux_output_match(event, group_leader))
		return 0;

	if (event->attr.aux_sample_size && !group_leader->pmu->snapshot_aux)
		return 0;

	if (!atomic_long_inc_not_zero(&group_leader->refcount))
		return 0;

	/*
	 * Link aux_outputs to their aux event; this is undone in
	 * perf_group_detach() by perf_put_aux_event(). When the
	 * group in torn down, the aux_output events loose their
	 * link to the aux_event and can't schedule any more.
	 */
	event->aux_event = group_leader;

	return 1;
}

static inline struct list_head *get_event_list(struct perf_event *event)
{
	return event->attr.pinned ? &event->pmu_ctx->pinned_active :
				    &event->pmu_ctx->flexible_active;
}

/*
 * Events that have PERF_EV_CAP_SIBLING require being part of a group and
 * cannot exist on their own, schedule them out and move them into the ERROR
 * state. Also see _perf_event_enable(), it will not be able to recover
 * this ERROR state.
 */
static inline void perf_remove_sibling_event(struct perf_event *event)
{
	event_sched_out(event, event->ctx);
	perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
}

static void perf_group_detach(struct perf_event *event)
{
	struct perf_event *leader = event->group_leader;
	struct perf_event *sibling, *tmp;
	struct perf_event_context *ctx = event->ctx;

	lockdep_assert_held(&ctx->lock);

	/*
	 * We can have double detach due to exit/hot-unplug + close.
	 */
	if (!(event->attach_state & PERF_ATTACH_GROUP))
		return;

	event->attach_state &= ~PERF_ATTACH_GROUP;

	perf_put_aux_event(event);

	/*
	 * If this is a sibling, remove it from its group.
	 */
	if (leader != event) {
		list_del_init(&event->sibling_list);
		event->group_leader->nr_siblings--;
		goto out;
	}

	/*
	 * If this was a group event with sibling events then
	 * upgrade the siblings to singleton events by adding them
	 * to whatever list we are on.
	 */
	list_for_each_entry_safe(sibling, tmp, &event->sibling_list, sibling_list) {

		if (sibling->event_caps & PERF_EV_CAP_SIBLING)
			perf_remove_sibling_event(sibling);

		sibling->group_leader = sibling;
		list_del_init(&sibling->sibling_list);

		/* Inherit group flags from the previous leader */
		sibling->group_caps = event->group_caps;

		if (sibling->attach_state & PERF_ATTACH_CONTEXT) {
			add_event_to_groups(sibling, event->ctx);

			if (sibling->state == PERF_EVENT_STATE_ACTIVE)
				list_add_tail(&sibling->active_list, get_event_list(sibling));
		}

		WARN_ON_ONCE(sibling->ctx != event->ctx);
	}

out:
	for_each_sibling_event(tmp, leader)
		perf_event__header_size(tmp);

	perf_event__header_size(leader);
}

static void sync_child_event(struct perf_event *child_event);

static void perf_child_detach(struct perf_event *event)
{
	struct perf_event *parent_event = event->parent;

	if (!(event->attach_state & PERF_ATTACH_CHILD))
		return;

	event->attach_state &= ~PERF_ATTACH_CHILD;

	if (WARN_ON_ONCE(!parent_event))
		return;

	lockdep_assert_held(&parent_event->child_mutex);

	sync_child_event(event);
	list_del_init(&event->child_list);
}

static bool is_orphaned_event(struct perf_event *event)
{
	return event->state == PERF_EVENT_STATE_DEAD;
}

static inline int
event_filter_match(struct perf_event *event)
{
	return (event->cpu == -1 || event->cpu == smp_processor_id()) &&
	       perf_cgroup_match(event);
}

static void
event_sched_out(struct perf_event *event, struct perf_event_context *ctx)
{
	struct perf_event_pmu_context *epc = event->pmu_ctx;
	struct perf_cpu_pmu_context *cpc = this_cpu_ptr(epc->pmu->cpu_pmu_context);
	enum perf_event_state state = PERF_EVENT_STATE_INACTIVE;

	// XXX cpc serialization, probably per-cpu IRQ disabled

	WARN_ON_ONCE(event->ctx != ctx);
	lockdep_assert_held(&ctx->lock);

	if (event->state != PERF_EVENT_STATE_ACTIVE)
		return;

	/*
	 * Asymmetry; we only schedule events _IN_ through ctx_sched_in(), but
	 * we can schedule events _OUT_ individually through things like
	 * __perf_remove_from_context().
	 */
	list_del_init(&event->active_list);

	perf_pmu_disable(event->pmu);

	event->pmu->del(event, 0);
	event->oncpu = -1;

	if (event->pending_disable) {
		event->pending_disable = 0;
		perf_cgroup_event_disable(event, ctx);
		state = PERF_EVENT_STATE_OFF;
	}

	if (event->pending_sigtrap) {
		bool dec = true;

		event->pending_sigtrap = 0;
		if (state != PERF_EVENT_STATE_OFF &&
		    !event->pending_work) {
			event->pending_work = 1;
			dec = false;
			WARN_ON_ONCE(!atomic_long_inc_not_zero(&event->refcount));
			task_work_add(current, &event->pending_task, TWA_RESUME);
		}
		if (dec)
			local_dec(&event->ctx->nr_pending);
	}

	perf_event_set_state(event, state);

	if (!is_software_event(event))
		cpc->active_oncpu--;
	if (event->attr.freq && event->attr.sample_freq)
		ctx->nr_freq--;
	if (event->attr.exclusive || !cpc->active_oncpu)
		cpc->exclusive = 0;

	perf_pmu_enable(event->pmu);
}

static void
group_sched_out(struct perf_event *group_event, struct perf_event_context *ctx)
{
	struct perf_event *event;

	if (group_event->state != PERF_EVENT_STATE_ACTIVE)
		return;

	perf_assert_pmu_disabled(group_event->pmu_ctx->pmu);

	event_sched_out(group_event, ctx);

	/*
	 * Schedule out siblings (if any):
	 */
	for_each_sibling_event(event, group_event)
		event_sched_out(event, ctx);
}

#define DETACH_GROUP	0x01UL
#define DETACH_CHILD	0x02UL
#define DETACH_DEAD	0x04UL

/*
 * Cross CPU call to remove a performance event
 *
 * We disable the event on the hardware level first. After that we
 * remove it from the context list.
 */
static void
__perf_remove_from_context(struct perf_event *event,
			   struct perf_cpu_context *cpuctx,
			   struct perf_event_context *ctx,
			   void *info)
{
	struct perf_event_pmu_context *pmu_ctx = event->pmu_ctx;
	unsigned long flags = (unsigned long)info;

	if (ctx->is_active & EVENT_TIME) {
		update_context_time(ctx);
		update_cgrp_time_from_cpuctx(cpuctx, false);
	}

	/*
	 * Ensure event_sched_out() switches to OFF, at the very least
	 * this avoids raising perf_pending_task() at this time.
	 */
	if (flags & DETACH_DEAD)
		event->pending_disable = 1;
	event_sched_out(event, ctx);
	if (flags & DETACH_GROUP)
		perf_group_detach(event);
	if (flags & DETACH_CHILD)
		perf_child_detach(event);
	list_del_event(event, ctx);
	if (flags & DETACH_DEAD)
		event->state = PERF_EVENT_STATE_DEAD;

	if (!pmu_ctx->nr_events) {
		pmu_ctx->rotate_necessary = 0;

		if (ctx->task && ctx->is_active) {
			struct perf_cpu_pmu_context *cpc;

			cpc = this_cpu_ptr(pmu_ctx->pmu->cpu_pmu_context);
			WARN_ON_ONCE(cpc->task_epc && cpc->task_epc != pmu_ctx);
			cpc->task_epc = NULL;
		}
	}

	if (!ctx->nr_events && ctx->is_active) {
		if (ctx == &cpuctx->ctx)
			update_cgrp_time_from_cpuctx(cpuctx, true);

		ctx->is_active = 0;
		if (ctx->task) {
			WARN_ON_ONCE(cpuctx->task_ctx != ctx);
			cpuctx->task_ctx = NULL;
		}
	}
}

/*
 * Remove the event from a task's (or a CPU's) list of events.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This is OK when called from perf_release since
 * that only calls us on the top-level context, which can't be a clone.
 * When called from perf_event_exit_task, it's OK because the
 * context has been detached from its task.
 */
static void perf_remove_from_context(struct perf_event *event, unsigned long flags)
{
	struct perf_event_context *ctx = event->ctx;

	lockdep_assert_held(&ctx->mutex);

	/*
	 * Because of perf_event_exit_task(), perf_remove_from_context() ought
	 * to work in the face of TASK_TOMBSTONE, unlike every other
	 * event_function_call() user.
	 */
	raw_spin_lock_irq(&ctx->lock);
	if (!ctx->is_active) {
		__perf_remove_from_context(event, this_cpu_ptr(&perf_cpu_context),
					   ctx, (void *)flags);
		raw_spin_unlock_irq(&ctx->lock);
		return;
	}
	raw_spin_unlock_irq(&ctx->lock);

	event_function_call(event, __perf_remove_from_context, (void *)flags);
}

/*
 * Cross CPU call to disable a performance event
 */
static void __perf_event_disable(struct perf_event *event,
				 struct perf_cpu_context *cpuctx,
				 struct perf_event_context *ctx,
				 void *info)
{
	if (event->state < PERF_EVENT_STATE_INACTIVE)
		return;

	if (ctx->is_active & EVENT_TIME) {
		update_context_time(ctx);
		update_cgrp_time_from_event(event);
	}

	perf_pmu_disable(event->pmu_ctx->pmu);

	if (event == event->group_leader)
		group_sched_out(event, ctx);
	else
		event_sched_out(event, ctx);

	perf_event_set_state(event, PERF_EVENT_STATE_OFF);
	perf_cgroup_event_disable(event, ctx);

	perf_pmu_enable(event->pmu_ctx->pmu);
}

/*
 * Disable an event.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This condition is satisfied when called through
 * perf_event_for_each_child or perf_event_for_each because they
 * hold the top-level event's child_mutex, so any descendant that
 * goes to exit will block in perf_event_exit_event().
 *
 * When called from perf_pending_irq it's OK because event->ctx
 * is the current context on this CPU and preemption is disabled,
 * hence we can't get into perf_event_task_sched_out for this context.
 */
static void _perf_event_disable(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;

	raw_spin_lock_irq(&ctx->lock);
	if (event->state <= PERF_EVENT_STATE_OFF) {
		raw_spin_unlock_irq(&ctx->lock);
		return;
	}
	raw_spin_unlock_irq(&ctx->lock);

	event_function_call(event, __perf_event_disable, NULL);
}

void perf_event_disable_local(struct perf_event *event)
{
	event_function_local(event, __perf_event_disable, NULL);
}

/*
 * Strictly speaking kernel users cannot create groups and therefore this
 * interface does not need the perf_event_ctx_lock() magic.
 */
void perf_event_disable(struct perf_event *event)
{
	struct perf_event_context *ctx;

	ctx = perf_event_ctx_lock(event);
	_perf_event_disable(event);
	perf_event_ctx_unlock(event, ctx);
}
EXPORT_SYMBOL_GPL(perf_event_disable);

void perf_event_disable_inatomic(struct perf_event *event)
{
	event->pending_disable = 1;
	irq_work_queue(&event->pending_irq);
}

#define MAX_INTERRUPTS (~0ULL)

static void perf_log_throttle(struct perf_event *event, int enable);
static void perf_log_itrace_start(struct perf_event *event);

static int
event_sched_in(struct perf_event *event, struct perf_event_context *ctx)
{
	struct perf_event_pmu_context *epc = event->pmu_ctx;
	struct perf_cpu_pmu_context *cpc = this_cpu_ptr(epc->pmu->cpu_pmu_context);
	int ret = 0;

	WARN_ON_ONCE(event->ctx != ctx);

	lockdep_assert_held(&ctx->lock);

	if (event->state <= PERF_EVENT_STATE_OFF)
		return 0;

	WRITE_ONCE(event->oncpu, smp_processor_id());
	/*
	 * Order event::oncpu write to happen before the ACTIVE state is
	 * visible. This allows perf_event_{stop,read}() to observe the correct
	 * ->oncpu if it sees ACTIVE.
	 */
	smp_wmb();
	perf_event_set_state(event, PERF_EVENT_STATE_ACTIVE);

	/*
	 * Unthrottle events, since we scheduled we might have missed several
	 * ticks already, also for a heavily scheduling task there is little
	 * guarantee it'll get a tick in a timely manner.
	 */
	if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
		perf_log_throttle(event, 1);
		event->hw.interrupts = 0;
	}

	perf_pmu_disable(event->pmu);

	perf_log_itrace_start(event);

	if (event->pmu->add(event, PERF_EF_START)) {
		perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);
		event->oncpu = -1;
		ret = -EAGAIN;
		goto out;
	}

	if (!is_software_event(event))
		cpc->active_oncpu++;
	if (event->attr.freq && event->attr.sample_freq)
		ctx->nr_freq++;

	if (event->attr.exclusive)
		cpc->exclusive = 1;

out:
	perf_pmu_enable(event->pmu);

	return ret;
}

static int
group_sched_in(struct perf_event *group_event, struct perf_event_context *ctx)
{
	struct perf_event *event, *partial_group = NULL;
	struct pmu *pmu = group_event->pmu_ctx->pmu;

	if (group_event->state == PERF_EVENT_STATE_OFF)
		return 0;

	pmu->start_txn(pmu, PERF_PMU_TXN_ADD);

	if (event_sched_in(group_event, ctx))
		goto error;

	/*
	 * Schedule in siblings as one group (if any):
	 */
	for_each_sibling_event(event, group_event) {
		if (event_sched_in(event, ctx)) {
			partial_group = event;
			goto group_error;
		}
	}

	if (!pmu->commit_txn(pmu))
		return 0;

group_error:
	/*
	 * Groups can be scheduled in as one unit only, so undo any
	 * partial group before returning:
	 * The events up to the failed event are scheduled out normally.
	 */
	for_each_sibling_event(event, group_event) {
		if (event == partial_group)
			break;

		event_sched_out(event, ctx);
	}
	event_sched_out(group_event, ctx);

error:
	pmu->cancel_txn(pmu);
	return -EAGAIN;
}

/*
 * Work out whether we can put this event group on the CPU now.
 */
static int group_can_go_on(struct perf_event *event, int can_add_hw)
{
	struct perf_event_pmu_context *epc = event->pmu_ctx;
	struct perf_cpu_pmu_context *cpc = this_cpu_ptr(epc->pmu->cpu_pmu_context);

	/*
	 * Groups consisting entirely of software events can always go on.
	 */
	if (event->group_caps & PERF_EV_CAP_SOFTWARE)
		return 1;
	/*
	 * If an exclusive group is already on, no other hardware
	 * events can go on.
	 */
	if (cpc->exclusive)
		return 0;
	/*
	 * If this group is exclusive and there are already
	 * events on the CPU, it can't go on.
	 */
	if (event->attr.exclusive && !list_empty(get_event_list(event)))
		return 0;
	/*
	 * Otherwise, try to add it if all previous groups were able
	 * to go on.
	 */
	return can_add_hw;
}

static void add_event_to_ctx(struct perf_event *event,
			       struct perf_event_context *ctx)
{
	list_add_event(event, ctx);
	perf_group_attach(event);
}

static void task_ctx_sched_out(struct perf_event_context *ctx,
				enum event_type_t event_type)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);

	if (!cpuctx->task_ctx)
		return;

	if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
		return;

	ctx_sched_out(ctx, event_type);
}

static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
				struct perf_event_context *ctx)
{
	ctx_sched_in(&cpuctx->ctx, EVENT_PINNED);
	if (ctx)
		 ctx_sched_in(ctx, EVENT_PINNED);
	ctx_sched_in(&cpuctx->ctx, EVENT_FLEXIBLE);
	if (ctx)
		 ctx_sched_in(ctx, EVENT_FLEXIBLE);
}

/*
 * We want to maintain the following priority of scheduling:
 *  - CPU pinned (EVENT_CPU | EVENT_PINNED)
 *  - task pinned (EVENT_PINNED)
 *  - CPU flexible (EVENT_CPU | EVENT_FLEXIBLE)
 *  - task flexible (EVENT_FLEXIBLE).
 *
 * In order to avoid unscheduling and scheduling back in everything every
 * time an event is added, only do it for the groups of equal priority and
 * below.
 *
 * This can be called after a batch operation on task events, in which case
 * event_type is a bit mask of the types of events involved. For CPU events,
 * event_type is only either EVENT_PINNED or EVENT_FLEXIBLE.
 */
/*
 * XXX: ctx_resched() reschedule entire perf_event_context while adding new
 * event to the context or enabling existing event in the context. We can
 * probably optimize it by rescheduling only affected pmu_ctx.
 */
static void ctx_resched(struct perf_cpu_context *cpuctx,
			struct perf_event_context *task_ctx,
			enum event_type_t event_type)
{
	bool cpu_event = !!(event_type & EVENT_CPU);

	/*
	 * If pinned groups are involved, flexible groups also need to be
	 * scheduled out.
	 */
	if (event_type & EVENT_PINNED)
		event_type |= EVENT_FLEXIBLE;

	event_type &= EVENT_ALL;

	perf_ctx_disable(&cpuctx->ctx);
	if (task_ctx) {
		perf_ctx_disable(task_ctx);
		task_ctx_sched_out(task_ctx, event_type);
	}

	/*
	 * Decide which cpu ctx groups to schedule out based on the types
	 * of events that caused rescheduling:
	 *  - EVENT_CPU: schedule out corresponding groups;
	 *  - EVENT_PINNED task events: schedule out EVENT_FLEXIBLE groups;
	 *  - otherwise, do nothing more.
	 */
	if (cpu_event)
		ctx_sched_out(&cpuctx->ctx, event_type);
	else if (event_type & EVENT_PINNED)
		ctx_sched_out(&cpuctx->ctx, EVENT_FLEXIBLE);

	perf_event_sched_in(cpuctx, task_ctx);

	perf_ctx_enable(&cpuctx->ctx);
	if (task_ctx)
		perf_ctx_enable(task_ctx);
}

void perf_pmu_resched(struct pmu *pmu)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_context *task_ctx = cpuctx->task_ctx;

	perf_ctx_lock(cpuctx, task_ctx);
	ctx_resched(cpuctx, task_ctx, EVENT_ALL|EVENT_CPU);
	perf_ctx_unlock(cpuctx, task_ctx);
}

/*
 * Cross CPU call to install and enable a performance event
 *
 * Very similar to remote_function() + event_function() but cannot assume that
 * things like ctx->is_active and cpuctx->task_ctx are set.
 */
static int  __perf_install_in_context(void *info)
{
	struct perf_event *event = info;
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_context *task_ctx = cpuctx->task_ctx;
	bool reprogram = true;
	int ret = 0;

	raw_spin_lock(&cpuctx->ctx.lock);
	if (ctx->task) {
		raw_spin_lock(&ctx->lock);
		task_ctx = ctx;

		reprogram = (ctx->task == current);

		/*
		 * If the task is running, it must be running on this CPU,
		 * otherwise we cannot reprogram things.
		 *
		 * If its not running, we don't care, ctx->lock will
		 * serialize against it becoming runnable.
		 */
		if (task_curr(ctx->task) && !reprogram) {
			ret = -ESRCH;
			goto unlock;
		}

		WARN_ON_ONCE(reprogram && cpuctx->task_ctx && cpuctx->task_ctx != ctx);
	} else if (task_ctx) {
		raw_spin_lock(&task_ctx->lock);
	}

#ifdef CONFIG_CGROUP_PERF
	if (event->state > PERF_EVENT_STATE_OFF && is_cgroup_event(event)) {
		/*
		 * If the current cgroup doesn't match the event's
		 * cgroup, we should not try to schedule it.
		 */
		struct perf_cgroup *cgrp = perf_cgroup_from_task(current, ctx);
		reprogram = cgroup_is_descendant(cgrp->css.cgroup,
					event->cgrp->css.cgroup);
	}
#endif

	if (reprogram) {
		ctx_sched_out(ctx, EVENT_TIME);
		add_event_to_ctx(event, ctx);
		ctx_resched(cpuctx, task_ctx, get_event_type(event));
	} else {
		add_event_to_ctx(event, ctx);
	}

unlock:
	perf_ctx_unlock(cpuctx, task_ctx);

	return ret;
}

static bool exclusive_event_installable(struct perf_event *event,
					struct perf_event_context *ctx);

/*
 * Attach a performance event to a context.
 *
 * Very similar to event_function_call, see comment there.
 */
static void
perf_install_in_context(struct perf_event_context *ctx,
			struct perf_event *event,
			int cpu)
{
	struct task_struct *task = READ_ONCE(ctx->task);

	lockdep_assert_held(&ctx->mutex);

	WARN_ON_ONCE(!exclusive_event_installable(event, ctx));

	if (event->cpu != -1)
		WARN_ON_ONCE(event->cpu != cpu);

	/*
	 * Ensures that if we can observe event->ctx, both the event and ctx
	 * will be 'complete'. See perf_iterate_sb_cpu().
	 */
	smp_store_release(&event->ctx, ctx);

	/*
	 * perf_event_attr::disabled events will not run and can be initialized
	 * without IPI. Except when this is the first event for the context, in
	 * that case we need the magic of the IPI to set ctx->is_active.
	 *
	 * The IOC_ENABLE that is sure to follow the creation of a disabled
	 * event will issue the IPI and reprogram the hardware.
	 */
	if (__perf_effective_state(event) == PERF_EVENT_STATE_OFF &&
	    ctx->nr_events && !is_cgroup_event(event)) {
		raw_spin_lock_irq(&ctx->lock);
		if (ctx->task == TASK_TOMBSTONE) {
			raw_spin_unlock_irq(&ctx->lock);
			return;
		}
		add_event_to_ctx(event, ctx);
		raw_spin_unlock_irq(&ctx->lock);
		return;
	}

	if (!task) {
		cpu_function_call(cpu, __perf_install_in_context, event);
		return;
	}

	/*
	 * Should not happen, we validate the ctx is still alive before calling.
	 */
	if (WARN_ON_ONCE(task == TASK_TOMBSTONE))
		return;

	/*
	 * Installing events is tricky because we cannot rely on ctx->is_active
	 * to be set in case this is the nr_events 0 -> 1 transition.
	 *
	 * Instead we use task_curr(), which tells us if the task is running.
	 * However, since we use task_curr() outside of rq::lock, we can race
	 * against the actual state. This means the result can be wrong.
	 *
	 * If we get a false positive, we retry, this is harmless.
	 *
	 * If we get a false negative, things are complicated. If we are after
	 * perf_event_context_sched_in() ctx::lock will serialize us, and the
	 * value must be correct. If we're before, it doesn't matter since
	 * perf_event_context_sched_in() will program the counter.
	 *
	 * However, this hinges on the remote context switch having observed
	 * our task->perf_event_ctxp[] store, such that it will in fact take
	 * ctx::lock in perf_event_context_sched_in().
	 *
	 * We do this by task_function_call(), if the IPI fails to hit the task
	 * we know any future context switch of task must see the
	 * perf_event_ctpx[] store.
	 */

	/*
	 * This smp_mb() orders the task->perf_event_ctxp[] store with the
	 * task_cpu() load, such that if the IPI then does not find the task
	 * running, a future context switch of that task must observe the
	 * store.
	 */
	smp_mb();
again:
	if (!task_function_call(task, __perf_install_in_context, event))
		return;

	raw_spin_lock_irq(&ctx->lock);
	task = ctx->task;
	if (WARN_ON_ONCE(task == TASK_TOMBSTONE)) {
		/*
		 * Cannot happen because we already checked above (which also
		 * cannot happen), and we hold ctx->mutex, which serializes us
		 * against perf_event_exit_task_context().
		 */
		raw_spin_unlock_irq(&ctx->lock);
		return;
	}
	/*
	 * If the task is not running, ctx->lock will avoid it becoming so,
	 * thus we can safely install the event.
	 */
	if (task_curr(task)) {
		raw_spin_unlock_irq(&ctx->lock);
		goto again;
	}
	add_event_to_ctx(event, ctx);
	raw_spin_unlock_irq(&ctx->lock);
}

/*
 * Cross CPU call to enable a performance event
 */
static void __perf_event_enable(struct perf_event *event,
				struct perf_cpu_context *cpuctx,
				struct perf_event_context *ctx,
				void *info)
{
	struct perf_event *leader = event->group_leader;
	struct perf_event_context *task_ctx;

	if (event->state >= PERF_EVENT_STATE_INACTIVE ||
	    event->state <= PERF_EVENT_STATE_ERROR)
		return;

	if (ctx->is_active)
		ctx_sched_out(ctx, EVENT_TIME);

	perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);
	perf_cgroup_event_enable(event, ctx);

	if (!ctx->is_active)
		return;

	if (!event_filter_match(event)) {
		ctx_sched_in(ctx, EVENT_TIME);
		return;
	}

	/*
	 * If the event is in a group and isn't the group leader,
	 * then don't put it on unless the group is on.
	 */
	if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) {
		ctx_sched_in(ctx, EVENT_TIME);
		return;
	}

	task_ctx = cpuctx->task_ctx;
	if (ctx->task)
		WARN_ON_ONCE(task_ctx != ctx);

	ctx_resched(cpuctx, task_ctx, get_event_type(event));
}

/*
 * Enable an event.
 *
 * If event->ctx is a cloned context, callers must make sure that
 * every task struct that event->ctx->task could possibly point to
 * remains valid.  This condition is satisfied when called through
 * perf_event_for_each_child or perf_event_for_each as described
 * for perf_event_disable.
 */
static void _perf_event_enable(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;

	raw_spin_lock_irq(&ctx->lock);
	if (event->state >= PERF_EVENT_STATE_INACTIVE ||
	    event->state <  PERF_EVENT_STATE_ERROR) {
out:
		raw_spin_unlock_irq(&ctx->lock);
		return;
	}

	/*
	 * If the event is in error state, clear that first.
	 *
	 * That way, if we see the event in error state below, we know that it
	 * has gone back into error state, as distinct from the task having
	 * been scheduled away before the cross-call arrived.
	 */
	if (event->state == PERF_EVENT_STATE_ERROR) {
		/*
		 * Detached SIBLING events cannot leave ERROR state.
		 */
		if (event->event_caps & PERF_EV_CAP_SIBLING &&
		    event->group_leader == event)
			goto out;

		event->state = PERF_EVENT_STATE_OFF;
	}
	raw_spin_unlock_irq(&ctx->lock);

	event_function_call(event, __perf_event_enable, NULL);
}

/*
 * See perf_event_disable();
 */
void perf_event_enable(struct perf_event *event)
{
	struct perf_event_context *ctx;

	ctx = perf_event_ctx_lock(event);
	_perf_event_enable(event);
	perf_event_ctx_unlock(event, ctx);
}
EXPORT_SYMBOL_GPL(perf_event_enable);

struct stop_event_data {
	struct perf_event	*event;
	unsigned int		restart;
};

static int __perf_event_stop(void *info)
{
	struct stop_event_data *sd = info;
	struct perf_event *event = sd->event;

	/* if it's already INACTIVE, do nothing */
	if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
		return 0;

	/* matches smp_wmb() in event_sched_in() */
	smp_rmb();

	/*
	 * There is a window with interrupts enabled before we get here,
	 * so we need to check again lest we try to stop another CPU's event.
	 */
	if (READ_ONCE(event->oncpu) != smp_processor_id())
		return -EAGAIN;

	event->pmu->stop(event, PERF_EF_UPDATE);

	/*
	 * May race with the actual stop (through perf_pmu_output_stop()),
	 * but it is only used for events with AUX ring buffer, and such
	 * events will refuse to restart because of rb::aux_mmap_count==0,
	 * see comments in perf_aux_output_begin().
	 *
	 * Since this is happening on an event-local CPU, no trace is lost
	 * while restarting.
	 */
	if (sd->restart)
		event->pmu->start(event, 0);

	return 0;
}

static int perf_event_stop(struct perf_event *event, int restart)
{
	struct stop_event_data sd = {
		.event		= event,
		.restart	= restart,
	};
	int ret = 0;

	do {
		if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
			return 0;

		/* matches smp_wmb() in event_sched_in() */
		smp_rmb();

		/*
		 * We only want to restart ACTIVE events, so if the event goes
		 * inactive here (event->oncpu==-1), there's nothing more to do;
		 * fall through with ret==-ENXIO.
		 */
		ret = cpu_function_call(READ_ONCE(event->oncpu),
					__perf_event_stop, &sd);
	} while (ret == -EAGAIN);

	return ret;
}

/*
 * In order to contain the amount of racy and tricky in the address filter
 * configuration management, it is a two part process:
 *
 * (p1) when userspace mappings change as a result of (1) or (2) or (3) below,
 *      we update the addresses of corresponding vmas in
 *	event::addr_filter_ranges array and bump the event::addr_filters_gen;
 * (p2) when an event is scheduled in (pmu::add), it calls
 *      perf_event_addr_filters_sync() which calls pmu::addr_filters_sync()
 *      if the generation has changed since the previous call.
 *
 * If (p1) happens while the event is active, we restart it to force (p2).
 *
 * (1) perf_addr_filters_apply(): adjusting filters' offsets based on
 *     pre-existing mappings, called once when new filters arrive via SET_FILTER
 *     ioctl;
 * (2) perf_addr_filters_adjust(): adjusting filters' offsets based on newly
 *     registered mapping, called for every new mmap(), with mm::mmap_lock down
 *     for reading;
 * (3) perf_event_addr_filters_exec(): clearing filters' offsets in the process
 *     of exec.
 */
void perf_event_addr_filters_sync(struct perf_event *event)
{
	struct perf_addr_filters_head *ifh = perf_event_addr_filters(event);

	if (!has_addr_filter(event))
		return;

	raw_spin_lock(&ifh->lock);
	if (event->addr_filters_gen != event->hw.addr_filters_gen) {
		event->pmu->addr_filters_sync(event);
		event->hw.addr_filters_gen = event->addr_filters_gen;
	}
	raw_spin_unlock(&ifh->lock);
}
EXPORT_SYMBOL_GPL(perf_event_addr_filters_sync);

static int _perf_event_refresh(struct perf_event *event, int refresh)
{
	/*
	 * not supported on inherited events
	 */
	if (event->attr.inherit || !is_sampling_event(event))
		return -EINVAL;

	atomic_add(refresh, &event->event_limit);
	_perf_event_enable(event);

	return 0;
}

/*
 * See perf_event_disable()
 */
int perf_event_refresh(struct perf_event *event, int refresh)
{
	struct perf_event_context *ctx;
	int ret;

	ctx = perf_event_ctx_lock(event);
	ret = _perf_event_refresh(event, refresh);
	perf_event_ctx_unlock(event, ctx);

	return ret;
}
EXPORT_SYMBOL_GPL(perf_event_refresh);

static int perf_event_modify_breakpoint(struct perf_event *bp,
					 struct perf_event_attr *attr)
{
	int err;

	_perf_event_disable(bp);

	err = modify_user_hw_breakpoint_check(bp, attr, true);

	if (!bp->attr.disabled)
		_perf_event_enable(bp);

	return err;
}

/*
 * Copy event-type-independent attributes that may be modified.
 */
static void perf_event_modify_copy_attr(struct perf_event_attr *to,
					const struct perf_event_attr *from)
{
	to->sig_data = from->sig_data;
}

static int perf_event_modify_attr(struct perf_event *event,
				  struct perf_event_attr *attr)
{
	int (*func)(struct perf_event *, struct perf_event_attr *);
	struct perf_event *child;
	int err;

	if (event->attr.type != attr->type)
		return -EINVAL;

	switch (event->attr.type) {
	case PERF_TYPE_BREAKPOINT:
		func = perf_event_modify_breakpoint;
		break;
	default:
		/* Place holder for future additions. */
		return -EOPNOTSUPP;
	}

	WARN_ON_ONCE(event->ctx->parent_ctx);

	mutex_lock(&event->child_mutex);
	/*
	 * Event-type-independent attributes must be copied before event-type
	 * modification, which will validate that final attributes match the
	 * source attributes after all relevant attributes have been copied.
	 */
	perf_event_modify_copy_attr(&event->attr, attr);
	err = func(event, attr);
	if (err)
		goto out;
	list_for_each_entry(child, &event->child_list, child_list) {
		perf_event_modify_copy_attr(&child->attr, attr);
		err = func(child, attr);
		if (err)
			goto out;
	}
out:
	mutex_unlock(&event->child_mutex);
	return err;
}

static void __pmu_ctx_sched_out(struct perf_event_pmu_context *pmu_ctx,
				enum event_type_t event_type)
{
	struct perf_event_context *ctx = pmu_ctx->ctx;
	struct perf_event *event, *tmp;
	struct pmu *pmu = pmu_ctx->pmu;

	if (ctx->task && !ctx->is_active) {
		struct perf_cpu_pmu_context *cpc;

		cpc = this_cpu_ptr(pmu->cpu_pmu_context);
		WARN_ON_ONCE(cpc->task_epc && cpc->task_epc != pmu_ctx);
		cpc->task_epc = NULL;
	}

	if (!event_type)
		return;

	perf_pmu_disable(pmu);
	if (event_type & EVENT_PINNED) {
		list_for_each_entry_safe(event, tmp,
					 &pmu_ctx->pinned_active,
					 active_list)
			group_sched_out(event, ctx);
	}

	if (event_type & EVENT_FLEXIBLE) {
		list_for_each_entry_safe(event, tmp,
					 &pmu_ctx->flexible_active,
					 active_list)
			group_sched_out(event, ctx);
		/*
		 * Since we cleared EVENT_FLEXIBLE, also clear
		 * rotate_necessary, is will be reset by
		 * ctx_flexible_sched_in() when needed.
		 */
		pmu_ctx->rotate_necessary = 0;
	}
	perf_pmu_enable(pmu);
}

static void
ctx_sched_out(struct perf_event_context *ctx, enum event_type_t event_type)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_pmu_context *pmu_ctx;
	int is_active = ctx->is_active;

	lockdep_assert_held(&ctx->lock);

	if (likely(!ctx->nr_events)) {
		/*
		 * See __perf_remove_from_context().
		 */
		WARN_ON_ONCE(ctx->is_active);
		if (ctx->task)
			WARN_ON_ONCE(cpuctx->task_ctx);
		return;
	}

	/*
	 * Always update time if it was set; not only when it changes.
	 * Otherwise we can 'forget' to update time for any but the last
	 * context we sched out. For example:
	 *
	 *   ctx_sched_out(.event_type = EVENT_FLEXIBLE)
	 *   ctx_sched_out(.event_type = EVENT_PINNED)
	 *
	 * would only update time for the pinned events.
	 */
	if (is_active & EVENT_TIME) {
		/* update (and stop) ctx time */
		update_context_time(ctx);
		update_cgrp_time_from_cpuctx(cpuctx, ctx == &cpuctx->ctx);
		/*
		 * CPU-release for the below ->is_active store,
		 * see __load_acquire() in perf_event_time_now()
		 */
		barrier();
	}

	ctx->is_active &= ~event_type;
	if (!(ctx->is_active & EVENT_ALL))
		ctx->is_active = 0;

	if (ctx->task) {
		WARN_ON_ONCE(cpuctx->task_ctx != ctx);
		if (!ctx->is_active)
			cpuctx->task_ctx = NULL;
	}

	is_active ^= ctx->is_active; /* changed bits */

	list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry)
		__pmu_ctx_sched_out(pmu_ctx, is_active);
}

/*
 * Test whether two contexts are equivalent, i.e. whether they have both been
 * cloned from the same version of the same context.
 *
 * Equivalence is measured using a generation number in the context that is
 * incremented on each modification to it; see unclone_ctx(), list_add_event()
 * and list_del_event().
 */
static int context_equiv(struct perf_event_context *ctx1,
			 struct perf_event_context *ctx2)
{
	lockdep_assert_held(&ctx1->lock);
	lockdep_assert_held(&ctx2->lock);

	/* Pinning disables the swap optimization */
	if (ctx1->pin_count || ctx2->pin_count)
		return 0;

	/* If ctx1 is the parent of ctx2 */
	if (ctx1 == ctx2->parent_ctx && ctx1->generation == ctx2->parent_gen)
		return 1;

	/* If ctx2 is the parent of ctx1 */
	if (ctx1->parent_ctx == ctx2 && ctx1->parent_gen == ctx2->generation)
		return 1;

	/*
	 * If ctx1 and ctx2 have the same parent; we flatten the parent
	 * hierarchy, see perf_event_init_context().
	 */
	if (ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx &&
			ctx1->parent_gen == ctx2->parent_gen)
		return 1;

	/* Unmatched */
	return 0;
}

static void __perf_event_sync_stat(struct perf_event *event,
				     struct perf_event *next_event)
{
	u64 value;

	if (!event->attr.inherit_stat)
		return;

	/*
	 * Update the event value, we cannot use perf_event_read()
	 * because we're in the middle of a context switch and have IRQs
	 * disabled, which upsets smp_call_function_single(), however
	 * we know the event must be on the current CPU, therefore we
	 * don't need to use it.
	 */
	if (event->state == PERF_EVENT_STATE_ACTIVE)
		event->pmu->read(event);

	perf_event_update_time(event);

	/*
	 * In order to keep per-task stats reliable we need to flip the event
	 * values when we flip the contexts.
	 */
	value = local64_read(&next_event->count);
	value = local64_xchg(&event->count, value);
	local64_set(&next_event->count, value);

	swap(event->total_time_enabled, next_event->total_time_enabled);
	swap(event->total_time_running, next_event->total_time_running);

	/*
	 * Since we swizzled the values, update the user visible data too.
	 */
	perf_event_update_userpage(event);
	perf_event_update_userpage(next_event);
}

static void perf_event_sync_stat(struct perf_event_context *ctx,
				   struct perf_event_context *next_ctx)
{
	struct perf_event *event, *next_event;

	if (!ctx->nr_stat)
		return;

	update_context_time(ctx);

	event = list_first_entry(&ctx->event_list,
				   struct perf_event, event_entry);

	next_event = list_first_entry(&next_ctx->event_list,
					struct perf_event, event_entry);

	while (&event->event_entry != &ctx->event_list &&
	       &next_event->event_entry != &next_ctx->event_list) {

		__perf_event_sync_stat(event, next_event);

		event = list_next_entry(event, event_entry);
		next_event = list_next_entry(next_event, event_entry);
	}
}

#define double_list_for_each_entry(pos1, pos2, head1, head2, member)	\
	for (pos1 = list_first_entry(head1, typeof(*pos1), member),	\
	     pos2 = list_first_entry(head2, typeof(*pos2), member);	\
	     !list_entry_is_head(pos1, head1, member) &&		\
	     !list_entry_is_head(pos2, head2, member);			\
	     pos1 = list_next_entry(pos1, member),			\
	     pos2 = list_next_entry(pos2, member))

static void perf_event_swap_task_ctx_data(struct perf_event_context *prev_ctx,
					  struct perf_event_context *next_ctx)
{
	struct perf_event_pmu_context *prev_epc, *next_epc;

	if (!prev_ctx->nr_task_data)
		return;

	double_list_for_each_entry(prev_epc, next_epc,
				   &prev_ctx->pmu_ctx_list, &next_ctx->pmu_ctx_list,
				   pmu_ctx_entry) {

		if (WARN_ON_ONCE(prev_epc->pmu != next_epc->pmu))
			continue;

		/*
		 * PMU specific parts of task perf context can require
		 * additional synchronization. As an example of such
		 * synchronization see implementation details of Intel
		 * LBR call stack data profiling;
		 */
		if (prev_epc->pmu->swap_task_ctx)
			prev_epc->pmu->swap_task_ctx(prev_epc, next_epc);
		else
			swap(prev_epc->task_ctx_data, next_epc->task_ctx_data);
	}
}

static void perf_ctx_sched_task_cb(struct perf_event_context *ctx, bool sched_in)
{
	struct perf_event_pmu_context *pmu_ctx;
	struct perf_cpu_pmu_context *cpc;

	list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry) {
		cpc = this_cpu_ptr(pmu_ctx->pmu->cpu_pmu_context);

		if (cpc->sched_cb_usage && pmu_ctx->pmu->sched_task)
			pmu_ctx->pmu->sched_task(pmu_ctx, sched_in);
	}
}

static void
perf_event_context_sched_out(struct task_struct *task, struct task_struct *next)
{
	struct perf_event_context *ctx = task->perf_event_ctxp;
	struct perf_event_context *next_ctx;
	struct perf_event_context *parent, *next_parent;
	int do_switch = 1;

	if (likely(!ctx))
		return;

	rcu_read_lock();
	next_ctx = rcu_dereference(next->perf_event_ctxp);
	if (!next_ctx)
		goto unlock;

	parent = rcu_dereference(ctx->parent_ctx);
	next_parent = rcu_dereference(next_ctx->parent_ctx);

	/* If neither context have a parent context; they cannot be clones. */
	if (!parent && !next_parent)
		goto unlock;

	if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
		/*
		 * Looks like the two contexts are clones, so we might be
		 * able to optimize the context switch.  We lock both
		 * contexts and check that they are clones under the
		 * lock (including re-checking that neither has been
		 * uncloned in the meantime).  It doesn't matter which
		 * order we take the locks because no other cpu could
		 * be trying to lock both of these tasks.
		 */
		raw_spin_lock(&ctx->lock);
		raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
		if (context_equiv(ctx, next_ctx)) {

			perf_ctx_disable(ctx);

			/* PMIs are disabled; ctx->nr_pending is stable. */
			if (local_read(&ctx->nr_pending) ||
			    local_read(&next_ctx->nr_pending)) {
				/*
				 * Must not swap out ctx when there's pending
				 * events that rely on the ctx->task relation.
				 */
				raw_spin_unlock(&next_ctx->lock);
				rcu_read_unlock();
				goto inside_switch;
			}

			WRITE_ONCE(ctx->task, next);
			WRITE_ONCE(next_ctx->task, task);

			perf_ctx_sched_task_cb(ctx, false);
			perf_event_swap_task_ctx_data(ctx, next_ctx);

			perf_ctx_enable(ctx);

			/*
			 * RCU_INIT_POINTER here is safe because we've not
			 * modified the ctx and the above modification of
			 * ctx->task and ctx->task_ctx_data are immaterial
			 * since those values are always verified under
			 * ctx->lock which we're now holding.
			 */
			RCU_INIT_POINTER(task->perf_event_ctxp, next_ctx);
			RCU_INIT_POINTER(next->perf_event_ctxp, ctx);

			do_switch = 0;

			perf_event_sync_stat(ctx, next_ctx);
		}
		raw_spin_unlock(&next_ctx->lock);
		raw_spin_unlock(&ctx->lock);
	}
unlock:
	rcu_read_unlock();

	if (do_switch) {
		raw_spin_lock(&ctx->lock);
		perf_ctx_disable(ctx);

inside_switch:
		perf_ctx_sched_task_cb(ctx, false);
		task_ctx_sched_out(ctx, EVENT_ALL);

		perf_ctx_enable(ctx);
		raw_spin_unlock(&ctx->lock);
	}
}

static DEFINE_PER_CPU(struct list_head, sched_cb_list);
static DEFINE_PER_CPU(int, perf_sched_cb_usages);

void perf_sched_cb_dec(struct pmu *pmu)
{
	struct perf_cpu_pmu_context *cpc = this_cpu_ptr(pmu->cpu_pmu_context);

	this_cpu_dec(perf_sched_cb_usages);
	barrier();

	if (!--cpc->sched_cb_usage)
		list_del(&cpc->sched_cb_entry);
}


void perf_sched_cb_inc(struct pmu *pmu)
{
	struct perf_cpu_pmu_context *cpc = this_cpu_ptr(pmu->cpu_pmu_context);

	if (!cpc->sched_cb_usage++)
		list_add(&cpc->sched_cb_entry, this_cpu_ptr(&sched_cb_list));

	barrier();
	this_cpu_inc(perf_sched_cb_usages);
}

/*
 * This function provides the context switch callback to the lower code
 * layer. It is invoked ONLY when the context switch callback is enabled.
 *
 * This callback is relevant even to per-cpu events; for example multi event
 * PEBS requires this to provide PID/TID information. This requires we flush
 * all queued PEBS records before we context switch to a new task.
 */
static void __perf_pmu_sched_task(struct perf_cpu_pmu_context *cpc, bool sched_in)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct pmu *pmu;

	pmu = cpc->epc.pmu;

	/* software PMUs will not have sched_task */
	if (WARN_ON_ONCE(!pmu->sched_task))
		return;

	perf_ctx_lock(cpuctx, cpuctx->task_ctx);
	perf_pmu_disable(pmu);

	pmu->sched_task(cpc->task_epc, sched_in);

	perf_pmu_enable(pmu);
	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
}

static void perf_pmu_sched_task(struct task_struct *prev,
				struct task_struct *next,
				bool sched_in)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_cpu_pmu_context *cpc;

	/* cpuctx->task_ctx will be handled in perf_event_context_sched_in/out */
	if (prev == next || cpuctx->task_ctx)
		return;

	list_for_each_entry(cpc, this_cpu_ptr(&sched_cb_list), sched_cb_entry)
		__perf_pmu_sched_task(cpc, sched_in);
}

static void perf_event_switch(struct task_struct *task,
			      struct task_struct *next_prev, bool sched_in);

/*
 * Called from scheduler to remove the events of the current task,
 * with interrupts disabled.
 *
 * We stop each event and update the event value in event->count.
 *
 * This does not protect us against NMI, but disable()
 * sets the disabled bit in the control field of event _before_
 * accessing the event control register. If a NMI hits, then it will
 * not restart the event.
 */
void __perf_event_task_sched_out(struct task_struct *task,
				 struct task_struct *next)
{
	if (__this_cpu_read(perf_sched_cb_usages))
		perf_pmu_sched_task(task, next, false);

	if (atomic_read(&nr_switch_events))
		perf_event_switch(task, next, false);

	perf_event_context_sched_out(task, next);

	/*
	 * if cgroup events exist on this CPU, then we need
	 * to check if we have to switch out PMU state.
	 * cgroup event are system-wide mode only
	 */
	perf_cgroup_switch(next);
}

static bool perf_less_group_idx(const void *l, const void *r)
{
	const struct perf_event *le = *(const struct perf_event **)l;
	const struct perf_event *re = *(const struct perf_event **)r;

	return le->group_index < re->group_index;
}

static void swap_ptr(void *l, void *r)
{
	void **lp = l, **rp = r;

	swap(*lp, *rp);
}

static const struct min_heap_callbacks perf_min_heap = {
	.elem_size = sizeof(struct perf_event *),
	.less = perf_less_group_idx,
	.swp = swap_ptr,
};

static void __heap_add(struct min_heap *heap, struct perf_event *event)
{
	struct perf_event **itrs = heap->data;

	if (event) {
		itrs[heap->nr] = event;
		heap->nr++;
	}
}

static void __link_epc(struct perf_event_pmu_context *pmu_ctx)
{
	struct perf_cpu_pmu_context *cpc;

	if (!pmu_ctx->ctx->task)
		return;

	cpc = this_cpu_ptr(pmu_ctx->pmu->cpu_pmu_context);
	WARN_ON_ONCE(cpc->task_epc && cpc->task_epc != pmu_ctx);
	cpc->task_epc = pmu_ctx;
}

static noinline int visit_groups_merge(struct perf_event_context *ctx,
				struct perf_event_groups *groups, int cpu,
				struct pmu *pmu,
				int (*func)(struct perf_event *, void *),
				void *data)
{
#ifdef CONFIG_CGROUP_PERF
	struct cgroup_subsys_state *css = NULL;
#endif
	struct perf_cpu_context *cpuctx = NULL;
	/* Space for per CPU and/or any CPU event iterators. */
	struct perf_event *itrs[2];
	struct min_heap event_heap;
	struct perf_event **evt;
	int ret;

	if (pmu->filter && pmu->filter(pmu, cpu))
		return 0;

	if (!ctx->task) {
		cpuctx = this_cpu_ptr(&perf_cpu_context);
		event_heap = (struct min_heap){
			.data = cpuctx->heap,
			.nr = 0,
			.size = cpuctx->heap_size,
		};

		lockdep_assert_held(&cpuctx->ctx.lock);

#ifdef CONFIG_CGROUP_PERF
		if (cpuctx->cgrp)
			css = &cpuctx->cgrp->css;
#endif
	} else {
		event_heap = (struct min_heap){
			.data = itrs,
			.nr = 0,
			.size = ARRAY_SIZE(itrs),
		};
		/* Events not within a CPU context may be on any CPU. */
		__heap_add(&event_heap, perf_event_groups_first(groups, -1, pmu, NULL));
	}
	evt = event_heap.data;

	__heap_add(&event_heap, perf_event_groups_first(groups, cpu, pmu, NULL));

#ifdef CONFIG_CGROUP_PERF
	for (; css; css = css->parent)
		__heap_add(&event_heap, perf_event_groups_first(groups, cpu, pmu, css->cgroup));
#endif

	if (event_heap.nr) {
		__link_epc((*evt)->pmu_ctx);
		perf_assert_pmu_disabled((*evt)->pmu_ctx->pmu);
	}

	min_heapify_all(&event_heap, &perf_min_heap);

	while (event_heap.nr) {
		ret = func(*evt, data);
		if (ret)
			return ret;

		*evt = perf_event_groups_next(*evt, pmu);
		if (*evt)
			min_heapify(&event_heap, 0, &perf_min_heap);
		else
			min_heap_pop(&event_heap, &perf_min_heap);
	}

	return 0;
}

/*
 * Because the userpage is strictly per-event (there is no concept of context,
 * so there cannot be a context indirection), every userpage must be updated
 * when context time starts :-(
 *
 * IOW, we must not miss EVENT_TIME edges.
 */
static inline bool event_update_userpage(struct perf_event *event)
{
	if (likely(!atomic_read(&event->mmap_count)))
		return false;

	perf_event_update_time(event);
	perf_event_update_userpage(event);

	return true;
}

static inline void group_update_userpage(struct perf_event *group_event)
{
	struct perf_event *event;

	if (!event_update_userpage(group_event))
		return;

	for_each_sibling_event(event, group_event)
		event_update_userpage(event);
}

static int merge_sched_in(struct perf_event *event, void *data)
{
	struct perf_event_context *ctx = event->ctx;
	int *can_add_hw = data;

	if (event->state <= PERF_EVENT_STATE_OFF)
		return 0;

	if (!event_filter_match(event))
		return 0;

	if (group_can_go_on(event, *can_add_hw)) {
		if (!group_sched_in(event, ctx))
			list_add_tail(&event->active_list, get_event_list(event));
	}

	if (event->state == PERF_EVENT_STATE_INACTIVE) {
		*can_add_hw = 0;
		if (event->attr.pinned) {
			perf_cgroup_event_disable(event, ctx);
			perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
		} else {
			struct perf_cpu_pmu_context *cpc;

			event->pmu_ctx->rotate_necessary = 1;
			cpc = this_cpu_ptr(event->pmu_ctx->pmu->cpu_pmu_context);
			perf_mux_hrtimer_restart(cpc);
			group_update_userpage(event);
		}
	}

	return 0;
}

static void ctx_pinned_sched_in(struct perf_event_context *ctx, struct pmu *pmu)
{
	struct perf_event_pmu_context *pmu_ctx;
	int can_add_hw = 1;

	if (pmu) {
		visit_groups_merge(ctx, &ctx->pinned_groups,
				   smp_processor_id(), pmu,
				   merge_sched_in, &can_add_hw);
	} else {
		list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry) {
			can_add_hw = 1;
			visit_groups_merge(ctx, &ctx->pinned_groups,
					   smp_processor_id(), pmu_ctx->pmu,
					   merge_sched_in, &can_add_hw);
		}
	}
}

static void ctx_flexible_sched_in(struct perf_event_context *ctx, struct pmu *pmu)
{
	struct perf_event_pmu_context *pmu_ctx;
	int can_add_hw = 1;

	if (pmu) {
		visit_groups_merge(ctx, &ctx->flexible_groups,
				   smp_processor_id(), pmu,
				   merge_sched_in, &can_add_hw);
	} else {
		list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry) {
			can_add_hw = 1;
			visit_groups_merge(ctx, &ctx->flexible_groups,
					   smp_processor_id(), pmu_ctx->pmu,
					   merge_sched_in, &can_add_hw);
		}
	}
}

static void __pmu_ctx_sched_in(struct perf_event_context *ctx, struct pmu *pmu)
{
	ctx_flexible_sched_in(ctx, pmu);
}

static void
ctx_sched_in(struct perf_event_context *ctx, enum event_type_t event_type)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	int is_active = ctx->is_active;

	lockdep_assert_held(&ctx->lock);

	if (likely(!ctx->nr_events))
		return;

	if (!(is_active & EVENT_TIME)) {
		/* start ctx time */
		__update_context_time(ctx, false);
		perf_cgroup_set_timestamp(cpuctx);
		/*
		 * CPU-release for the below ->is_active store,
		 * see __load_acquire() in perf_event_time_now()
		 */
		barrier();
	}

	ctx->is_active |= (event_type | EVENT_TIME);
	if (ctx->task) {
		if (!is_active)
			cpuctx->task_ctx = ctx;
		else
			WARN_ON_ONCE(cpuctx->task_ctx != ctx);
	}

	is_active ^= ctx->is_active; /* changed bits */

	/*
	 * First go through the list and put on any pinned groups
	 * in order to give them the best chance of going on.
	 */
	if (is_active & EVENT_PINNED)
		ctx_pinned_sched_in(ctx, NULL);

	/* Then walk through the lower prio flexible groups */
	if (is_active & EVENT_FLEXIBLE)
		ctx_flexible_sched_in(ctx, NULL);
}

static void perf_event_context_sched_in(struct task_struct *task)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_context *ctx;

	rcu_read_lock();
	ctx = rcu_dereference(task->perf_event_ctxp);
	if (!ctx)
		goto rcu_unlock;

	if (cpuctx->task_ctx == ctx) {
		perf_ctx_lock(cpuctx, ctx);
		perf_ctx_disable(ctx);

		perf_ctx_sched_task_cb(ctx, true);

		perf_ctx_enable(ctx);
		perf_ctx_unlock(cpuctx, ctx);
		goto rcu_unlock;
	}

	perf_ctx_lock(cpuctx, ctx);
	/*
	 * We must check ctx->nr_events while holding ctx->lock, such
	 * that we serialize against perf_install_in_context().
	 */
	if (!ctx->nr_events)
		goto unlock;

	perf_ctx_disable(ctx);
	/*
	 * We want to keep the following priority order:
	 * cpu pinned (that don't need to move), task pinned,
	 * cpu flexible, task flexible.
	 *
	 * However, if task's ctx is not carrying any pinned
	 * events, no need to flip the cpuctx's events around.
	 */
	if (!RB_EMPTY_ROOT(&ctx->pinned_groups.tree)) {
		perf_ctx_disable(&cpuctx->ctx);
		ctx_sched_out(&cpuctx->ctx, EVENT_FLEXIBLE);
	}

	perf_event_sched_in(cpuctx, ctx);

	perf_ctx_sched_task_cb(cpuctx->task_ctx, true);

	if (!RB_EMPTY_ROOT(&ctx->pinned_groups.tree))
		perf_ctx_enable(&cpuctx->ctx);

	perf_ctx_enable(ctx);

unlock:
	perf_ctx_unlock(cpuctx, ctx);
rcu_unlock:
	rcu_read_unlock();
}

/*
 * Called from scheduler to add the events of the current task
 * with interrupts disabled.
 *
 * We restore the event value and then enable it.
 *
 * This does not protect us against NMI, but enable()
 * sets the enabled bit in the control field of event _before_
 * accessing the event control register. If a NMI hits, then it will
 * keep the event running.
 */
void __perf_event_task_sched_in(struct task_struct *prev,
				struct task_struct *task)
{
	perf_event_context_sched_in(task);

	if (atomic_read(&nr_switch_events))
		perf_event_switch(task, prev, true);

	if (__this_cpu_read(perf_sched_cb_usages))
		perf_pmu_sched_task(prev, task, true);
}

static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
{
	u64 frequency = event->attr.sample_freq;
	u64 sec = NSEC_PER_SEC;
	u64 divisor, dividend;

	int count_fls, nsec_fls, frequency_fls, sec_fls;

	count_fls = fls64(count);
	nsec_fls = fls64(nsec);
	frequency_fls = fls64(frequency);
	sec_fls = 30;

	/*
	 * We got @count in @nsec, with a target of sample_freq HZ
	 * the target period becomes:
	 *
	 *             @count * 10^9
	 * period = -------------------
	 *          @nsec * sample_freq
	 *
	 */

	/*
	 * Reduce accuracy by one bit such that @a and @b converge
	 * to a similar magnitude.
	 */
#define REDUCE_FLS(a, b)		\
do {					\
	if (a##_fls > b##_fls) {	\
		a >>= 1;		\
		a##_fls--;		\
	} else {			\
		b >>= 1;		\
		b##_fls--;		\
	}				\
} while (0)

	/*
	 * Reduce accuracy until either term fits in a u64, then proceed with
	 * the other, so that finally we can do a u64/u64 division.
	 */
	while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
		REDUCE_FLS(nsec, frequency);
		REDUCE_FLS(sec, count);
	}

	if (count_fls + sec_fls > 64) {
		divisor = nsec * frequency;

		while (count_fls + sec_fls > 64) {
			REDUCE_FLS(count, sec);
			divisor >>= 1;
		}

		dividend = count * sec;
	} else {
		dividend = count * sec;

		while (nsec_fls + frequency_fls > 64) {
			REDUCE_FLS(nsec, frequency);
			dividend >>= 1;
		}

		divisor = nsec * frequency;
	}

	if (!divisor)
		return dividend;

	return div64_u64(dividend, divisor);
}

static DEFINE_PER_CPU(int, perf_throttled_count);
static DEFINE_PER_CPU(u64, perf_throttled_seq);

static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bool disable)
{
	struct hw_perf_event *hwc = &event->hw;
	s64 period, sample_period;
	s64 delta;

	period = perf_calculate_period(event, nsec, count);

	delta = (s64)(period - hwc->sample_period);
	delta = (delta + 7) / 8; /* low pass filter */

	sample_period = hwc->sample_period + delta;

	if (!sample_period)
		sample_period = 1;

	hwc->sample_period = sample_period;

	if (local64_read(&hwc->period_left) > 8*sample_period) {
		if (disable)
			event->pmu->stop(event, PERF_EF_UPDATE);

		local64_set(&hwc->period_left, 0);

		if (disable)
			event->pmu->start(event, PERF_EF_RELOAD);
	}
}

/*
 * combine freq adjustment with unthrottling to avoid two passes over the
 * events. At the same time, make sure, having freq events does not change
 * the rate of unthrottling as that would introduce bias.
 */
static void
perf_adjust_freq_unthr_context(struct perf_event_context *ctx, bool unthrottle)
{
	struct perf_event *event;
	struct hw_perf_event *hwc;
	u64 now, period = TICK_NSEC;
	s64 delta;

	/*
	 * only need to iterate over all events iff:
	 * - context have events in frequency mode (needs freq adjust)
	 * - there are events to unthrottle on this cpu
	 */
	if (!(ctx->nr_freq || unthrottle))
		return;

	raw_spin_lock(&ctx->lock);

	list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
		if (event->state != PERF_EVENT_STATE_ACTIVE)
			continue;

		// XXX use visit thingy to avoid the -1,cpu match
		if (!event_filter_match(event))
			continue;

		perf_pmu_disable(event->pmu);

		hwc = &event->hw;

		if (hwc->interrupts == MAX_INTERRUPTS) {
			hwc->interrupts = 0;
			perf_log_throttle(event, 1);
			event->pmu->start(event, 0);
		}

		if (!event->attr.freq || !event->attr.sample_freq)
			goto next;

		/*
		 * stop the event and update event->count
		 */
		event->pmu->stop(event, PERF_EF_UPDATE);

		now = local64_read(&event->count);
		delta = now - hwc->freq_count_stamp;
		hwc->freq_count_stamp = now;

		/*
		 * restart the event
		 * reload only if value has changed
		 * we have stopped the event so tell that
		 * to perf_adjust_period() to avoid stopping it
		 * twice.
		 */
		if (delta > 0)
			perf_adjust_period(event, period, delta, false);

		event->pmu->start(event, delta > 0 ? PERF_EF_RELOAD : 0);
	next:
		perf_pmu_enable(event->pmu);
	}

	raw_spin_unlock(&ctx->lock);
}

/*
 * Move @event to the tail of the @ctx's elegible events.
 */
static void rotate_ctx(struct perf_event_context *ctx, struct perf_event *event)
{
	/*
	 * Rotate the first entry last of non-pinned groups. Rotation might be
	 * disabled by the inheritance code.
	 */
	if (ctx->rotate_disable)
		return;

	perf_event_groups_delete(&ctx->flexible_groups, event);
	perf_event_groups_insert(&ctx->flexible_groups, event);
}

/* pick an event from the flexible_groups to rotate */
static inline struct perf_event *
ctx_event_to_rotate(struct perf_event_pmu_context *pmu_ctx)
{
	struct perf_event *event;
	struct rb_node *node;
	struct rb_root *tree;
	struct __group_key key = {
		.pmu = pmu_ctx->pmu,
	};

	/* pick the first active flexible event */
	event = list_first_entry_or_null(&pmu_ctx->flexible_active,
					 struct perf_event, active_list);
	if (event)
		goto out;

	/* if no active flexible event, pick the first event */
	tree = &pmu_ctx->ctx->flexible_groups.tree;

	if (!pmu_ctx->ctx->task) {
		key.cpu = smp_processor_id();

		node = rb_find_first(&key, tree, __group_cmp_ignore_cgroup);
		if (node)
			event = __node_2_pe(node);
		goto out;
	}

	key.cpu = -1;
	node = rb_find_first(&key, tree, __group_cmp_ignore_cgroup);
	if (node) {
		event = __node_2_pe(node);
		goto out;
	}

	key.cpu = smp_processor_id();
	node = rb_find_first(&key, tree, __group_cmp_ignore_cgroup);
	if (node)
		event = __node_2_pe(node);

out:
	/*
	 * Unconditionally clear rotate_necessary; if ctx_flexible_sched_in()
	 * finds there are unschedulable events, it will set it again.
	 */
	pmu_ctx->rotate_necessary = 0;

	return event;
}

static bool perf_rotate_context(struct perf_cpu_pmu_context *cpc)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_pmu_context *cpu_epc, *task_epc = NULL;
	struct perf_event *cpu_event = NULL, *task_event = NULL;
	int cpu_rotate, task_rotate;
	struct pmu *pmu;

	/*
	 * Since we run this from IRQ context, nobody can install new
	 * events, thus the event count values are stable.
	 */

	cpu_epc = &cpc->epc;
	pmu = cpu_epc->pmu;
	task_epc = cpc->task_epc;

	cpu_rotate = cpu_epc->rotate_necessary;
	task_rotate = task_epc ? task_epc->rotate_necessary : 0;

	if (!(cpu_rotate || task_rotate))
		return false;

	perf_ctx_lock(cpuctx, cpuctx->task_ctx);
	perf_pmu_disable(pmu);

	if (task_rotate)
		task_event = ctx_event_to_rotate(task_epc);
	if (cpu_rotate)
		cpu_event = ctx_event_to_rotate(cpu_epc);

	/*
	 * As per the order given at ctx_resched() first 'pop' task flexible
	 * and then, if needed CPU flexible.
	 */
	if (task_event || (task_epc && cpu_event)) {
		update_context_time(task_epc->ctx);
		__pmu_ctx_sched_out(task_epc, EVENT_FLEXIBLE);
	}

	if (cpu_event) {
		update_context_time(&cpuctx->ctx);
		__pmu_ctx_sched_out(cpu_epc, EVENT_FLEXIBLE);
		rotate_ctx(&cpuctx->ctx, cpu_event);
		__pmu_ctx_sched_in(&cpuctx->ctx, pmu);
	}

	if (task_event)
		rotate_ctx(task_epc->ctx, task_event);

	if (task_event || (task_epc && cpu_event))
		__pmu_ctx_sched_in(task_epc->ctx, pmu);

	perf_pmu_enable(pmu);
	perf_ctx_unlock(cpuctx, cpuctx->task_ctx);

	return true;
}

void perf_event_task_tick(void)
{
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct perf_event_context *ctx;
	int throttled;

	lockdep_assert_irqs_disabled();

	__this_cpu_inc(perf_throttled_seq);
	throttled = __this_cpu_xchg(perf_throttled_count, 0);
	tick_dep_clear_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS);

	perf_adjust_freq_unthr_context(&cpuctx->ctx, !!throttled);

	rcu_read_lock();
	ctx = rcu_dereference(current->perf_event_ctxp);
	if (ctx)
		perf_adjust_freq_unthr_context(ctx, !!throttled);
	rcu_read_unlock();
}

static int event_enable_on_exec(struct perf_event *event,
				struct perf_event_context *ctx)
{
	if (!event->attr.enable_on_exec)
		return 0;

	event->attr.enable_on_exec = 0;
	if (event->state >= PERF_EVENT_STATE_INACTIVE)
		return 0;

	perf_event_set_state(event, PERF_EVENT_STATE_INACTIVE);

	return 1;
}

/*
 * Enable all of a task's events that have been marked enable-on-exec.
 * This expects task == current.
 */
static void perf_event_enable_on_exec(struct perf_event_context *ctx)
{
	struct perf_event_context *clone_ctx = NULL;
	enum event_type_t event_type = 0;
	struct perf_cpu_context *cpuctx;
	struct perf_event *event;
	unsigned long flags;
	int enabled = 0;

	local_irq_save(flags);
	if (WARN_ON_ONCE(current->perf_event_ctxp != ctx))
		goto out;

	if (!ctx->nr_events)
		goto out;

	cpuctx = this_cpu_ptr(&perf_cpu_context);
	perf_ctx_lock(cpuctx, ctx);
	ctx_sched_out(ctx, EVENT_TIME);

	list_for_each_entry(event, &ctx->event_list, event_entry) {
		enabled |= event_enable_on_exec(event, ctx);
		event_type |= get_event_type(event);
	}

	/*
	 * Unclone and reschedule this context if we enabled any event.
	 */
	if (enabled) {
		clone_ctx = unclone_ctx(ctx);
		ctx_resched(cpuctx, ctx, event_type);
	} else {
		ctx_sched_in(ctx, EVENT_TIME);
	}
	perf_ctx_unlock(cpuctx, ctx);

out:
	local_irq_restore(flags);

	if (clone_ctx)
		put_ctx(clone_ctx);
}

static void perf_remove_from_owner(struct perf_event *event);
static void perf_event_exit_event(struct perf_event *event,
				  struct perf_event_context *ctx);

/*
 * Removes all events from the current task that have been marked
 * remove-on-exec, and feeds their values back to parent events.
 */
static void perf_event_remove_on_exec(struct perf_event_context *ctx)
{
	struct perf_event_context *clone_ctx = NULL;
	struct perf_event *event, *next;
	unsigned long flags;
	bool modified = false;

	mutex_lock(&ctx->mutex);

	if (WARN_ON_ONCE(ctx->task != current))
		goto unlock;

	list_for_each_entry_safe(event, next, &ctx->event_list, event_entry) {
		if (!event->attr.remove_on_exec)
			continue;

		if (!is_kernel_event(event))
			perf_remove_from_owner(event);

		modified = true;

		perf_event_exit_event(event, ctx);
	}

	raw_spin_lock_irqsave(&ctx->lock, flags);
	if (modified)
		clone_ctx = unclone_ctx(ctx);
	raw_spin_unlock_irqrestore(&ctx->lock, flags);

unlock:
	mutex_unlock(&ctx->mutex);

	if (clone_ctx)
		put_ctx(clone_ctx);
}

struct perf_read_data {
	struct perf_event *event;
	bool group;
	int ret;
};

static int __perf_event_read_cpu(struct perf_event *event, int event_cpu)
{
	u16 local_pkg, event_pkg;

	if (event->group_caps & PERF_EV_CAP_READ_ACTIVE_PKG) {
		int local_cpu = smp_processor_id();

		event_pkg = topology_physical_package_id(event_cpu);
		local_pkg = topology_physical_package_id(local_cpu);

		if (event_pkg == local_pkg)
			return local_cpu;
	}

	return event_cpu;
}

/*
 * Cross CPU call to read the hardware event
 */
static void __perf_event_read(void *info)
{
	struct perf_read_data *data = info;
	struct perf_event *sub, *event = data->event;
	struct perf_event_context *ctx = event->ctx;
	struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
	struct pmu *pmu = event->pmu;

	/*
	 * If this is a task context, we need to check whether it is
	 * the current task context of this cpu.  If not it has been
	 * scheduled out before the smp call arrived.  In that case
	 * event->count would have been updated to a recent sample
	 * when the event was scheduled out.
	 */
	if (ctx->task && cpuctx->task_ctx != ctx)
		return;

	raw_spin_lock(&ctx->lock);
	if (ctx->is_active & EVENT_TIME) {
		update_context_time(ctx);
		update_cgrp_time_from_event(event);
	}

	perf_event_update_time(event);
	if (data->group)
		perf_event_update_sibling_time(event);

	if (event->state != PERF_EVENT_STATE_ACTIVE)
		goto unlock;

	if (!data->group) {
		pmu->read(event);
		data->ret = 0;
		goto unlock;
	}

	pmu->start_txn(pmu, PERF_PMU_TXN_READ);

	pmu->read(event);

	for_each_sibling_event(sub, event) {
		if (sub->state == PERF_EVENT_STATE_ACTIVE) {
			/*
			 * Use sibling's PMU rather than @event's since
			 * sibling could be on different (eg: software) PMU.
			 */
			sub->pmu->read(sub);
		}
	}

	data->ret = pmu->commit_txn(pmu);

unlock:
	raw_spin_unlock(&ctx->lock);
}

static inline u64 perf_event_count(struct perf_event *event)
{
	return local64_read(&event->count) + atomic64_read(&event->child_count);
}

static void calc_timer_values(struct perf_event *event,
				u64 *now,
				u64 *enabled,
				u64 *running)
{
	u64 ctx_time;

	*now = perf_clock();
	ctx_time = perf_event_time_now(event, *now);
	__perf_update_times(event, ctx_time, enabled, running);
}

/*
 * NMI-safe method to read a local event, that is an event that
 * is:
 *   - either for the current task, or for this CPU
 *   - does not have inherit set, for inherited task events
 *     will not be local and we cannot read them atomically
 *   - must not have a pmu::count method
 */
int perf_event_read_local(struct perf_event *event, u64 *value,
			  u64 *enabled, u64 *running)
{
	unsigned long flags;
	int ret = 0;

	/*
	 * Disabling interrupts avoids all counter scheduling (context
	 * switches, timer based rotation and IPIs).
	 */
	local_irq_save(flags);

	/*
	 * It must not be an event with inherit set, we cannot read
	 * all child counters from atomic context.
	 */
	if (event->attr.inherit) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	/* If this is a per-task event, it must be for current */
	if ((event->attach_state & PERF_ATTACH_TASK) &&
	    event->hw.target != current) {
		ret = -EINVAL;
		goto out;
	}

	/* If this is a per-CPU event, it must be for this CPU */
	if (!(event->attach_state & PERF_ATTACH_TASK) &&
	    event->cpu != smp_processor_id()) {
		ret = -EINVAL;
		goto out;
	}

	/* If this is a pinned event it must be running on this CPU */
	if (event->attr.pinned && event->oncpu != smp_processor_id()) {
		ret = -EBUSY;
		goto out;
	}

	/*
	 * If the event is currently on this CPU, its either a per-task event,
	 * or local to this CPU. Furthermore it means its ACTIVE (otherwise
	 * oncpu == -1).
	 */
	if (event->oncpu == smp_processor_id())
		event->pmu->read(event);

	*value = local64_read(&event->count);
	if (enabled || running) {
		u64 __enabled, __running, __now;

		calc_timer_values(event, &__now, &__enabled, &__running);
		if (enabled)
			*enabled = __enabled;
		if (running)
			*running = __running;
	}
out:
	local_irq_restore(flags);

	return ret;
}

static int perf_event_read(struct perf_event *event, bool group)
{
	enum perf_event_state state = READ_ONCE(event->state);
	int event_cpu, ret = 0;

	/*
	 * If event is enabled and currently active on a CPU, update the
	 * value in the event structure:
	 */
again:
	if (state == PERF_EVENT_STATE_ACTIVE) {
		struct perf_read_data data;

		/*
		 * Orders the ->state and ->oncpu loads such that if we see
		 * ACTIVE we must also see the right ->oncpu.
		 *
		 * Matches the smp_wmb() from event_sched_in().
		 */
		smp_rmb();

		event_cpu = READ_ONCE(event->oncpu);
		if ((unsigned)event_cpu >= nr_cpu_ids)
			return 0;

		data = (struct perf_read_data){
			.event = event,
			.group = group,
			.ret = 0,
		};

		preempt_disable();
		event_cpu = __perf_event_read_cpu(event, event_cpu);

		/*
		 * Purposely ignore the smp_call_function_single() return
		 * value.
		 *
		 * If event_cpu isn't a valid CPU it means the event got
		 * scheduled out and that will have updated the event count.
		 *
		 * Therefore, either way, we'll have an up-to-date event count
		 * after this.
		 */
		(void)smp_call_function_single(event_cpu, __perf_event_read, &data, 1);
		preempt_enable();
		ret = data.ret;

	} else if (state == PERF_EVENT_STATE_INACTIVE) {
		struct perf_event_context *ctx = event->ctx;
		unsigned long flags;

		raw_spin_lock_irqsave(&ctx->lock, flags);
		state = event->state;
		if (state != PERF_EVENT_STATE_INACTIVE) {
			raw_spin_unlock_irqrestore(&ctx->lock, flags);
			goto again;
		}

		/*
		 * May read while context is not active (e.g., thread is
		 * blocked), in that case we cannot update context time
		 */
		if (ctx->is_active & EVENT_TIME) {
			update_context_time(ctx);
			update_cgrp_time_from_event(event);
		}

		perf_event_update_time(event);
		if (group)
			perf_event_update_sibling_time(event);
		raw_spin_unlock_irqrestore(&ctx->lock, flags);
	}

	return ret;
}

/*
 * Initialize the perf_event context in a task_struct:
 */
static void __perf_event_init_context(struct perf_event_context *ctx)
{
	raw_spin_lock_init(&ctx->lock);
	mutex_init(&ctx->mutex);
	INIT_LIST_HEAD(&ctx->pmu_ctx_list);
	perf_event_groups_init(&ctx->pinned_groups);
	perf_event_groups_init(&ctx->flexible_groups);
	INIT_LIST_HEAD(&ctx->event_list);
	refcount_set(&ctx->refcount, 1);
}

static void
__perf_init_event_pmu_context(struct perf_event_pmu_context *epc, struct pmu *pmu)
{
	epc->pmu = pmu;
	INIT_LIST_HEAD(&epc->pmu_ctx_entry);
	INIT_LIST_HEAD(&epc->pinned_active);
	INIT_LIST_HEAD(&epc->flexible_active);
	atomic_set(&epc->refcount, 1);
}

static struct perf_event_context *
alloc_perf_context(struct task_struct *task)
{
	struct perf_event_context *ctx;

	ctx = kzalloc(sizeof(struct perf_event_context), GFP_KERNEL);
	if (!ctx)
		return NULL;

	__perf_event_init_context(ctx);
	if (task)
		ctx->task = get_task_struct(task);

	return ctx;
}

static struct task_struct *
find_lively_task_by_vpid(pid_t vpid)
{
	struct task_struct *task;

	rcu_read_lock();
	if (!vpid)
		task = current;
	else
		task = find_task_by_vpid(vpid);
	if (task)
		get_task_struct(task);
	rcu_read_unlock();

	if (!task)
		return ERR_PTR(-ESRCH);

	return task;
}

/*
 * Returns a matching context with refcount and pincount.
 */
static struct perf_event_context *
find_get_context(struct task_struct *task, struct perf_event *event)
{
	struct perf_event_context *ctx, *clone_ctx = NULL;
	struct perf_cpu_context *cpuctx;
	unsigned long flags;
	int err;

	if (!task) {
		/* Must be root to operate on a CPU event: */
		err = perf_allow_cpu(&event->attr);
		if (err)
			return ERR_PTR(err);

		cpuctx = per_cpu_ptr(&perf_cpu_context, event->cpu);
		ctx = &cpuctx->ctx;
		get_ctx(ctx);
		raw_spin_lock_irqsave(&ctx->lock, flags);
		++ctx->pin_count;
		raw_spin_unlock_irqrestore(&ctx->lock, flags);

		return ctx;
	}

	err = -EINVAL;
retry:
	ctx = perf_lock_task_context(task, &flags);
	if (ctx) {
		clone_ctx = unclone_ctx(ctx);
		++ctx->pin_count;

		raw_spin_unlock_irqrestore(&ctx->lock, flags);

		if (clone_ctx)
			put_ctx(clone_ctx);
	} else {
		ctx = alloc_perf_context(task);
		err = -ENOMEM;
		if (!ctx)
			goto errout;

		err = 0;
		mutex_lock(&task->perf_event_mutex);
		/*
		 * If it has already passed perf_event_exit_task().
		 * we must see PF_EXITING, it takes this mutex too.
		 */
		if (task->flags & PF_EXITING)
			err = -ESRCH;
		else if (task->perf_event_ctxp)
			err = -EAGAIN;
		else {
			get_ctx(ctx);
			++ctx->pin_count;
			rcu_assign_pointer(task->perf_event_ctxp, ctx);
		}
		mutex_unlock(&task->perf_event_mutex);

		if (unlikely(err)) {
			put_ctx(ctx);

			if (err == -EAGAIN)
				goto retry;
			goto errout;
		}
	}

	return ctx;

errout:
	return ERR_PTR(err);
}

static struct perf_event_pmu_context *
find_get_pmu_context(struct pmu *pmu, struct perf_event_context *ctx,
		     struct perf_event *event)
{
	struct perf_event_pmu_context *new = NULL, *epc;
	void *task_ctx_data = NULL;

	if (!ctx->task) {
		struct perf_cpu_pmu_context *cpc;

		cpc = per_cpu_ptr(pmu->cpu_pmu_context, event->cpu);
		epc = &cpc->epc;
		raw_spin_lock_irq(&ctx->lock);
		if (!epc->ctx) {
			atomic_set(&epc->refcount, 1);
			epc->embedded = 1;
			list_add(&epc->pmu_ctx_entry, &ctx->pmu_ctx_list);
			epc->ctx = ctx;
		} else {
			WARN_ON_ONCE(epc->ctx != ctx);
			atomic_inc(&epc->refcount);
		}
		raw_spin_unlock_irq(&ctx->lock);
		return epc;
	}

	new = kzalloc(sizeof(*epc), GFP_KERNEL);
	if (!new)
		return ERR_PTR(-ENOMEM);

	if (event->attach_state & PERF_ATTACH_TASK_DATA) {
		task_ctx_data = alloc_task_ctx_data(pmu);
		if (!task_ctx_data) {
			kfree(new);
			return ERR_PTR(-ENOMEM);
		}
	}

	__perf_init_event_pmu_context(new, pmu);

	/*
	 * XXX
	 *
	 * lockdep_assert_held(&ctx->mutex);
	 *
	 * can't because perf_event_init_task() doesn't actually hold the
	 * child_ctx->mutex.
	 */

	raw_spin_lock_irq(&ctx->lock);
	list_for_each_entry(epc, &ctx->pmu_ctx_list, pmu_ctx_entry) {
		if (epc->pmu == pmu) {
			WARN_ON_ONCE(epc->ctx != ctx);
			atomic_inc(&epc->refcount);
			goto found_epc;
		}
	}

	epc = new;
	new = NULL;

	list_add(&epc->pmu_ctx_entry, &ctx->pmu_ctx_list);
	epc->ctx = ctx;

found_epc:
	if (task_ctx_data && !epc->task_ctx_data) {
		epc->task_ctx_data = task_ctx_data;
		task_ctx_data = NULL;
		ctx->nr_task_data++;
	}
	raw_spin_unlock_irq(&ctx->lock);

	free_task_ctx_data(pmu, task_ctx_data);
	kfree(new);

	return epc;
}

static void get_pmu_ctx(struct perf_event_pmu_context *epc)
{
	WARN_ON_ONCE(!atomic_inc_not_zero(&epc->refcount));
}

static void free_epc_rcu(struct rcu_head *head)
{
	struct perf_event_pmu_context *epc = container_of(head, typeof(*epc), rcu_head);

	kfree(epc->task_ctx_data);
	kfree(epc);
}

static void put_pmu_ctx(struct perf_event_pmu_context *epc)
{
	struct perf_event_context *ctx = epc->ctx;
	unsigned long flags;

	/*
	 * XXX
	 *
	 * lockdep_assert_held(&ctx->mutex);
	 *
	 * can't because of the call-site in _free_event()/put_event()
	 * which isn't always called under ctx->mutex.
	 */
	if (!atomic_dec_and_raw_lock_irqsave(&epc->refcount, &ctx->lock, flags))
		return;

	WARN_ON_ONCE(list_empty(&epc->pmu_ctx_entry));

	list_del_init(&epc->pmu_ctx_entry);
	epc->ctx = NULL;

	WARN_ON_ONCE(!list_empty(&epc->pinned_active));
	WARN_ON_ONCE(!list_empty(&epc->flexible_active));

	raw_spin_unlock_irqrestore(&ctx->lock, flags);

	if (epc->embedded)
		return;

	call_rcu(&epc->rcu_head, free_epc_rcu);
}

static void perf_event_free_filter(struct perf_event *event);

static void free_event_rcu(struct rcu_head *head)
{
	struct perf_event *event = container_of(head, typeof(*event), rcu_head);

	if (event->ns)
		put_pid_ns(event->ns);
	perf_event_free_filter(event);
	kmem_cache_free(perf_event_cache, event);
}

static void ring_buffer_attach(struct perf_event *event,
			       struct perf_buffer *rb);

static void detach_sb_event(struct perf_event *event)
{
	struct pmu_event_list *pel = per_cpu_ptr(&pmu_sb_events, event->cpu);

	raw_spin_lock(&pel->lock);
	list_del_rcu(&event->sb_list);
	raw_spin_unlock(&pel->lock);
}

static bool is_sb_event(struct perf_event *event)
{
	struct perf_event_attr *attr = &event->attr;

	if (event->parent)
		return false;

	if (event->attach_state & PERF_ATTACH_TASK)
		return false;

	if (attr->mmap || attr->mmap_data || attr->mmap2 ||
	    attr->comm || attr->comm_exec ||
	    attr->task || attr->ksymbol ||
	    attr->context_switch || attr->text_poke ||
	    attr->bpf_event)
		return true;
	return false;
}

static void unaccount_pmu_sb_event(struct perf_event *event)
{
	if (is_sb_event(event))
		detach_sb_event(event);
}

#ifdef CONFIG_NO_HZ_FULL
static DEFINE_SPINLOCK(nr_freq_lock);
#endif

static void unaccount_freq_event_nohz(void)
{
#ifdef CONFIG_NO_HZ_FULL
	spin_lock(&nr_freq_lock);
	if (atomic_dec_and_test(&nr_freq_events))
		tick_nohz_dep_clear(TICK_DEP_BIT_PERF_EVENTS);
	spin_unlock(&nr_freq_lock);
#endif
}

static void unaccount_freq_event(void)
{
	if (tick_nohz_full_enabled())
		unaccount_freq_event_nohz();
	else
		atomic_dec(&nr_freq_events);
}

static void unaccount_event(struct perf_event *event)
{
	bool dec = false;

	if (event->parent)
		return;

	if (event->attach_state & (PERF_ATTACH_TASK | PERF_ATTACH_SCHED_CB))
		dec = true;
	if (event->attr.mmap || event->attr.mmap_data)
		atomic_dec(&nr_mmap_events);
	if (event->attr.build_id)
		atomic_dec(&nr_build_id_events);
	if (event->attr.comm)
		atomic_dec(&nr_comm_events);
	if (event->attr.namespaces)
		atomic_dec(&nr_namespaces_events);
	if (event->attr.cgroup)
		atomic_dec(&nr_cgroup_events);
	if (event->attr.task)
		atomic_dec(&nr_task_events);
	if (event->attr.freq)
		unaccount_freq_event();
	if (event->attr.context_switch) {
		dec = true;
		atomic_dec(&nr_switch_events);
	}
	if (is_cgroup_event(event))
		dec = true;
	if (has_branch_stack(event))
		dec = true;
	if (event->attr.ksymbol)
		atomic_dec(&nr_ksymbol_events);
	if (event->attr.bpf_event)
		atomic_dec(&nr_bpf_events);
	if (event->attr.text_poke)
		atomic_dec(&nr_text_poke_events);

	if (dec) {
		if (!atomic_add_unless(&perf_sched_count, -1, 1))
			schedule_delayed_work(&perf_sched_work, HZ);
	}

	unaccount_pmu_sb_event(event);
}

static void perf_sched_delayed(struct work_struct *work)
{
	mutex_lock(&perf_sched_mutex);
	if (atomic_dec_and_test(&perf_sched_count))
		static_branch_disable(&perf_sched_events);
	mutex_unlock(&perf_sched_mutex);
}

/*
 * The following implement mutual exclusion of events on "exclusive" pmus
 * (PERF_PMU_CAP_EXCLUSIVE). Such pmus can only have one event scheduled
 * at a time, so we disallow creating events that might conflict, namely:
 *
 *  1) cpu-wide events in the presence of per-task events,
 *  2) per-task events in the presence of cpu-wide events,
 *  3) two matching events on the same perf_event_context.
 *
 * The former two cases are handled in the allocation path (perf_event_alloc(),
 * _free_event()), the latter -- before the first perf_install_in_context().
 */
static int exclusive_event_init(struct perf_event *event)
{
	struct pmu *pmu = event->pmu;

	if (!is_exclusive_pmu(pmu))
		return 0;

	/*
	 * Prevent co-existence of per-task and cpu-wide events on the
	 * same exclusive pmu.
	 *
	 * Negative pmu::exclusive_cnt means there are cpu-wide
	 * events on this "exclusive" pmu, positive means there are
	 * per-task events.
	 *
	 * Since this is called in perf_event_alloc() path, event::ctx
	 * doesn't exist yet; it is, however, safe to use PERF_ATTACH_TASK
	 * to mean "per-task event", because unlike other attach states it
	 * never gets cleared.
	 */
	if (event->attach_state & PERF_ATTACH_TASK) {
		if (!atomic_inc_unless_negative(&pmu->exclusive_cnt))
			return -EBUSY;
	} else {
		if (!atomic_dec_unless_positive(&pmu->exclusive_cnt))
			return -EBUSY;
	}

	return 0;
}

static void exclusive_event_destroy(struct perf_event *event)
{
	struct pmu *pmu = event->pmu;

	if (!is_exclusive_pmu(pmu))
		return;

	/* see comment in exclusive_event_init() */
	if (event->attach_state & PERF_ATTACH_TASK)
		atomic_dec(&pmu->exclusive_cnt);
	else
		atomic_inc(&pmu->exclusive_cnt);
}

static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2)
{
	if ((e1->pmu == e2->pmu) &&
	    (e1->cpu == e2->cpu ||
	     e1->cpu == -1 ||
	     e2->cpu == -1))
		return true;
	return false;
}

static bool exclusive_event_installable(struct perf_event *event,
					struct perf_event_context *ctx)
{
	struct perf_event *iter_event;
	struct pmu *pmu = event->pmu;

	lockdep_assert_held(&ctx->mutex);

	if (!is_exclusive_pmu(pmu))
		return true;

	list_for_each_entry(iter_event, &ctx->event_list, event_entry) {
		if (exclusive_event_match(iter_event, event))
			return false;
	}

	return true;
}

static void perf_addr_filters_splice(struct perf_event *event,
				       struct list_head *head);

static void _free_event(struct perf_event *event)
{
	irq_work_sync(&event->pending_irq);

	unaccount_event(event);

	security_perf_event_free(event);

	if (event->rb) {
		/*
		 * Can happen when we close an event with re-directed output.
		 *
		 * Since we have a 0 refcount, perf_mmap_close() will skip
		 * over us; possibly making our ring_buffer_put() the last.
		 */
		mutex_lock(&event->mmap_mutex);
		ring_buffer_attach(event, NULL);
		mutex_unlock(&event->mmap_mutex);
	}

	if (is_cgroup_event(event))
		perf_detach_cgroup(event);

	if (!event->parent) {
		if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
			put_callchain_buffers();
	}

	perf_event_free_bpf_prog(event);
	perf_addr_filters_splice(event, NULL);
	kfree(event->addr_filter_ranges);

	if (event->destroy)
		event->destroy(event);

	/*
	 * Must be after ->destroy(), due to uprobe_perf_close() using
	 * hw.target.
	 */
	if (event->hw.target)
		put_task_struct(event->hw.target);

	if (event->pmu_ctx)
		put_pmu_ctx(event->pmu_ctx);

	/*
	 * perf_event_free_task() relies on put_ctx() being 'last', in particular
	 * all task references must be cleaned up.
	 */
	if (event->ctx)
		put_ctx(event->ctx);

	exclusive_event_destroy(event);
	module_put(event->pmu->module);

	call_rcu(&event->rcu_head, free_event_rcu);
}

/*
 * Used to free events which have a known refcount of 1, such as in error paths
 * where the event isn't exposed yet and inherited events.
 */
static void free_event(struct perf_event *event)
{
	if (WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1,
				"unexpected event refcount: %ld; ptr=%p\n",
				atomic_long_read(&event->refcount), event)) {
		/* leak to avoid use-after-free */
		return;
	}

	_free_event(event);
}

/*
 * Remove user event from the owner task.
 */
static void perf_remove_from_owner(struct perf_event *event)
{
	struct task_struct *owner;

	rcu_read_lock();
	/*
	 * Matches the smp_store_release() in perf_event_exit_task(). If we
	 * observe !owner it means the list deletion is complete and we can
	 * indeed free this event, otherwise we need to serialize on
	 * owner->perf_event_mutex.
	 */
	owner = READ_ONCE(event->owner);
	if (owner) {
		/*
		 * Since delayed_put_task_struct() also drops the last
		 * task reference we can safely take a new reference
		 * while holding the rcu_read_lock().
		 */
		get_task_struct(owner);
	}
	rcu_read_unlock();

	if (owner) {
		/*
		 * If we're here through perf_event_exit_task() we're already
		 * holding ctx->mutex which would be an inversion wrt. the
		 * normal lock order.
		 *
		 * However we can safely take this lock because its the child
		 * ctx->mutex.
		 */
		mutex_lock_nested(&owner->perf_event_mutex, SINGLE_DEPTH_NESTING);

		/*
		 * We have to re-check the event->owner field, if it is cleared
		 * we raced with perf_event_exit_task(), acquiring the mutex
		 * ensured they're done, and we can proceed with freeing the
		 * event.
		 */
		if (event->owner) {
			list_del_init(&event->owner_entry);
			smp_store_release(&event->owner, NULL);
		}
		mutex_unlock(&owner->perf_event_mutex);
		put_task_struct(owner);
	}
}

static void put_event(struct perf_event *event)
{
	if (!atomic_long_dec_and_test(&event->refcount))
		return;

	_free_event(event);
}

/*
 * Kill an event dead; while event:refcount will preserve the event
 * object, it will not preserve its functionality. Once the last 'user'
 * gives up the object, we'll destroy the thing.
 */
int perf_event_release_kernel(struct perf_event *event)
{
	struct perf_event_context *ctx = event->ctx;
	struct perf_event *child, *tmp;
	LIST_HEAD(free_list);

	/*
	 * If we got here through err_alloc: free_event(event); we will not
	 * have attached to a context yet.
	 */
	if (!ctx) {
		WARN_ON_ONCE(event->attach_state &
				(PERF_ATTACH_CONTEXT|PERF_ATTACH_GROUP));
		goto no_ctx;
	}

	if (!is_kernel_event(event))
		perf_remove_from_owner(event);

	ctx = perf_event_ctx_lock(event);
	WARN_ON_ONCE(ctx->parent_ctx);

	/*
	 * Mark this event as STATE_DEAD, there is no external reference to it
	 * anymore.
	 *
	 * Anybody acquiring event->child_mutex after the below loop _must_
	 * also see this, most importantly inherit_event() which will avoid
	 * placing more children on the list.
	 *
	 * Thus this guarantees that we will in fact observe and kill _ALL_
	 * child events.
	 */
	perf_remove_from_context(event, DETACH_GROUP|DETACH_DEAD);

	perf_event_ctx_unlock(event, ctx);

again:
	mutex_lock(&event->child_mutex);
	list_for_each_entry(child, &event->child_list, child_list) {

		/*
		 * Cannot change, child events are not migrated, see the
		 * comment with perf_event_ctx_lock_nested().
		 */
		ctx = READ_ONCE(child->ctx);
		/*
		 * Since child_mutex nests inside ctx::mutex, we must jump
		 * through hoops. We start by grabbing a reference on the ctx.
		 *
		 * Since the event cannot get freed while we hold the
		 * child_mutex, the context must also exist and have a !0
		 * reference count.
		 */
		get_ctx(ctx);

		/*
		 * Now that we have a ctx ref, we can drop child_mutex, and
		 * acquire ctx::mutex without fear of it going away. Then we
		 * can re-acquire child_mutex.
		 */
		mutex_unlock(&event->child_mutex);
		mutex_lock(&ctx->mutex);
		mutex_lock(&event->child_mutex);

		/*
		 * Now that we hold ctx::mutex and child_mutex, revalidate our
		 * state, if child is still the first entry, it didn't get freed
		 * and we can continue doing so.
		 */
		tmp = list_first_entry_or_null(&event->child_list,
					       struct perf_event, child_list);
		if (tmp == child) {
			perf_remove_from_context(child, DETACH_GROUP);
			list_move(&child->child_list, &free_list);
			/*
			 * This matches the refcount bump in inherit_event();
			 * this can't be the last reference.
			 */
			put_event(event);
		}

		mutex_unlock(&event->child_mutex);
		mutex_unlock(&ctx->mutex);
		put_ctx(ctx);
		goto again;
	}
	mutex_unlock(&event->child_mutex);

	list_for_each_entry_safe(child, tmp, &free_list, child_list) {
		void *var = &child->ctx->refcount;

		list_del(&child->child_list);
		free_event(child);

		/*
		 * Wake any perf_event_free_task() waiting for this event to be
		 * freed.
		 */
		smp_mb(); /* pairs with wait_var_event() */
		wake_up_var(var);
	}

no_ctx:
	put_event(event); /* Must be the 'last' reference */
	return 0;
}
EXPORT_SYMBOL_GPL(perf_event_release_kernel);

/*
 * Called when the last reference to the file is gone.
 */
static int perf_release(struct inode *inode, struct file *file)
{
	perf_event_release_kernel(file->private_data);
	return 0;
}

static u64 __perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
{
	struct perf_event *child;
	u64 total = 0;

	*enabled = 0;
	*running = 0;

	mutex_lock(&event->child_mutex);

	(void)perf_event_read(event, false);
	total += perf_event_count(event);

	*enabled += event->total_time_enabled +
			atomic64_read(&event->child_total_time_enabled);
	*running += event->total_time_running +
			atomic64_read(&event->child_total_time_running);

	list_for_each_entry(child, &event->child_list, child_list) {
		(void)perf_event_read(child, false);
		total += perf_event_count(child);
		*enabled += child->total_time_enabled;
		*running += child->total_time_running;
	}
	mutex_unlock(&event->child_mutex);

	return total;
}

u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
{
	struct perf_event_context *ctx;
	u64 count;

	ctx = perf_event_ctx_lock(event);
	count = __perf_event_read_value(event, enabled, running);
	perf_event_ctx_unlock(event, ctx);

	return count;
}
EXPORT_SYMBOL_GPL(perf_event_read_value);

static int __perf_read_group_add(struct perf_event *leader,
					u64 read_format, u64 *values)
{
	struct perf_event_context *ctx = leader->ctx;
	struct perf_event *sub;
	unsigned long flags;
	int n = 1; /* skip @nr */
	int ret;

	ret = perf_event_read(leader, true);
	if (ret)
		return ret;

	raw_spin_lock_irqsave(&ctx->lock, flags);

	/*
	 * Since we co-schedule groups, {enabled,running} times of siblings
	 * will be identical to those of the leader, so we only publish one
	 * set.
	 */
	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
		values[n++] += leader->total_time_enabled +
			atomic64_read(&leader->child_total_time_enabled);
	}

	if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
		values[n++] += leader->total_time_running +
			atomic64_read(&leader->child_total_time_running);
	}

	/*
	 * Write {count,id} tuples for every sibling.
	 */
	values[n++] += perf_event_count(leader);
	if (read_format & PERF_FORMAT_ID)
		values[n++] = primary_event_id(leader);
	if (read_format & PERF_FORMAT_LOST)
		values[n++] = atomic64_read(&leader->lost_samples);

	for_each_sibling_event(sub, leader) {
		values[n++] += perf_event_count(sub);
		if (read_format & PERF_FORMAT_ID)
			values[n++] = primary_event_id(sub);
		if (read_format & PERF_FORMAT_LOST)
			values[n++] = atomic64_read(&sub->lost_samples);
	}

	raw_spin_unlock_irqrestore(&ctx->lock, flags);
	return 0;
}

static int perf_read_group(struct perf_event *event,
				   u64 read_format, char __user *buf)
{
	struct perf_event *leader = event->group_leader, *child;
	struct perf_event_context *ctx = leader->ctx;
	int ret;
	u64 *values;

	lockdep_assert_held(&ctx->mutex);

	values = kzalloc(event->read_size, GFP_KERNEL);
	if (!values)
		return -ENOMEM;

	values[0] = 1 + leader->nr_siblings;

	/*
	 * By locking the child_mutex of the leader we effectively
	 * lock the child list of all siblings.. XXX explain how.
	 */
	mutex_lock(&leader->child_mutex);

	ret = __perf_read_group_add(leader, read_format, values);
	if (ret)
		goto unlock;

	list_for_each_entry(child, &leader->child_list, child_list) {
		ret = __perf_read_group_add(child, read_format, values);
		if (ret)
			goto unlock;
	}

	mutex_unlock(&leader->child_mutex);

	ret = event->read_size;
	if (copy_to_user(buf, values, event->read_size))
		ret = -EFAULT;
	goto out;

unlock:
	mutex_unlock(&leader->child_mutex);
out:
	kfree(values);
	return ret;
}

static int perf_read_one(struct perf_event *event,
				 u64 read_format, char __user *buf)
{
	u64 enabled, running;
	u64 values[5];
	int n = 0;

	values[n++] = __perf_event_read_value(event, &enabled, &running);
	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
		values[n++] = enabled;
	if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
		values[n++] = running;
	if (read_format & PERF_FORMAT_ID)
		values[n++] = primary_event_id(event);
	if (read_format & PERF_FORMAT_LOST)
		values[n++] = atomic64_read(&event->lost_samples);

	if (copy_to_user(buf, values, n * sizeof(u64)))
		return -EFAULT;

	return n * sizeof(u64);
}

static bool is_event_hup(struct perf_event *event)
{
	bool no_children;

	if (event->state > PERF_EVENT_STATE_EXIT)
		return false;

	mutex_lock(&event->child_mutex);
	no_children = list_empty(&event->child_list);
	mutex_unlock(&event->child_mutex);
	return no_children;
}

/*
 * Read the performance event - simple non blocking version for now
 */
static ssize_t
__perf_read(struct perf_event *event, char __user *buf, size_t count)
{
	u64 read_format = event->attr.read_format;
	int ret;

	/*
	 * Return end-of-file for a read on an event that is in
	 * error state (i.e. because it was pinned but it couldn't be
	 * scheduled on to the CPU at some point).
	 */
	if (event->state == PERF_EVENT_STATE_ERROR)
		return 0;

	if (count < event->read_size)
		return -ENOSPC;

	WARN_ON_ONCE(event->ctx->parent_ctx);
	if (read_format & PERF_FORMAT_GROUP)
		ret = perf_read_group(event, read_format, buf);
	else
		ret = perf_read_one(event, read_format, buf);

	return ret;
}

static ssize_t
perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
{
	struct perf_event *event = file->private_data;
	struct perf_event_context *ctx;
	int ret;

	ret = security_perf_event_read(event);
	if (ret)
		return ret;

	ctx = perf_event_ctx_lock(event);
	ret = __perf_read(event, buf, count);
	perf_event_ctx_unlock(event, ctx);

	return ret;
}

static __poll_t perf_poll(struct file *file, poll_table *wait)
{
	struct perf_event *event = file->private_data;
	struct perf_buffer *rb;
	__poll_t events = EPOLLHUP;

	poll_wait(file, &event->waitq, wait);

	if (is_event_hup(event))
		return events;

	/*
	 * Pin the event->rb by taking event->mmap_mutex; otherwise
	 * perf_event_set_output() can swizzle our rb and make us miss wakeups.
	 */
	mutex_lock(&event->mmap_mutex);
	rb = event->rb;
	if (rb)
		events = atomic_xchg(&rb->poll, 0);
	mutex_unlock(&event->mmap_mutex);
	return events;
}

static void _perf_event_reset(struct perf_event *event)
{
	(void)perf_event_read(event, false);
	local64_set(&event->count, 0);
	perf_event_update_userpage(event);
}

/* Assume it's not an event with inherit set. */
u64 perf_event_pause(struct perf_event *event, bool reset)
{
	struct perf_event_context *ctx;
	u64 count;

	ctx = perf_event_ctx_lock(event);
	WARN_ON_ONCE(event->attr.inherit);
	_perf_event_disable(event);
	count = local64_read(&event->count);
	if (reset)
		local64_set(&event->count, 0);
	perf_event_ctx_unlock(event, ctx);

	return count;
}
EXPORT_SYMBOL_GPL(perf_event_pause);

/*
 * Holding the top-level event's child_mutex means that any
 * descendant process that has inherited this event will block
 * in perf_event_exit_event() if it goes to exit, thus satisfying the
 * task existence requirements of perf_event_enable/disable.
 */
static void perf_event_for_each_child(struct perf_event *event,
					void (*func)(struct perf_event *))
{
	struct perf_event *child;

	WARN_ON_ONCE(event->ctx->parent_ctx);

	mutex_lock(&event->child_mutex);
	func(event);
	list_for_each_entry(child, &event->child_list, child_list)
		func(child);
	mutex_unlock(&event->child_mutex);
}

static void perf_event_for_each(struct perf_event *event,
				  void (*func)(struct perf_event *))
{
	struct perf_event_context *ctx = event->ctx;
	struct perf_event *sibling;

	lockdep_assert_held(&ctx->mutex);

	event = event->group_leader;

	perf_event_for_each_child(event, func);
	for_each_sibling_event(sibling, event)
		perf_event_for_each_child(sibling, func);
}

static void __perf_event_period(struct perf_event *event,
				struct perf_cpu_context *cpuctx,
				struct perf_event_context *ctx,
				void *info)
{
	u64 value = *((u64 *)info);
	bool active;

	if (event->attr.freq) {
		event->attr.sample_freq = value;
	} else {
		event->attr.sample_period = value;
		event->hw.sample_period = value;
	}

	active = (event->state == PERF_EVENT_STATE_ACTIVE);
	if (active) {
		perf_pmu_disable(event->pmu);
		/*
		 * We could be throttled; unthrottle now to avoid the tick
		 * trying to unthrottle while we already re-started the event.
		 */
		if (event->hw.interrupts == MAX_INTERRUPTS) {
			event->hw.interrupts = 0;
			perf_log_throttle(event, 1);
		}
		event->pmu->stop(event, PERF_EF_UPDATE);
	}

	local64_set(&event->hw.period_left, 0);

	if (active) {
		event->pmu->start(event, PERF_EF_RELOAD);
		perf_pmu_enable(event->pmu);
	}
}

static int perf_event_check_period(struct perf_event *event, u64 value)
{
	return event->pmu->check_period(event, value);
}

static int _perf_event_period(struct perf_event *event, u64 value)
{
	if (!is_sampling_event(event))
		return -EINVAL;

	if (!value)
		return -EINVAL;

	if (event->attr.freq && value > sysctl_perf_event_sample_rate)
		return -EINVAL;

	if (perf_event_check_period(event, value))
		return -EINVAL;

	if (!event->attr.freq && (value & (1ULL << 63)))
		return -EINVAL;

	event_function_call(event, __perf_event_period, &value);

	return 0;
}

int perf_event_period(struct perf_event *event, u64 value)
{
	struct perf_event_context *ctx;
	int ret;

	ctx = perf_event_ctx_lock(event);
	ret = _perf_event_period(event, value);
	perf_event_ctx_unlock(event, ctx);

	return ret;
}
EXPORT_SYMBOL_GPL(perf_event_period);

static const struct file_operations perf_fops;

static inline int perf_fget_light(int fd, struct fd *p)
{
	struct fd f = fdget(fd);
	if (!f.file)
		return -EBADF;

	if (f.file->f_op != &perf_fops) {
		fdput(f);
		return -EBADF;
	}
	*p = f;
	return 0;
}

static int perf_event_set_output(struct perf_event *event,
				 struct perf_event *output_event);
static int perf_event_set_filter(struct perf_event *event, void __user *arg);
static int perf_copy_attr(struct perf_event_attr __user *uattr,
			  struct perf_event_attr *attr);

static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned long arg)
{
	void (*func)(struct perf_event *);
	u32 flags = arg;

	switch (cmd) {
	case PERF_EVENT_IOC_ENABLE:
		func = _perf_event_enable;
		break;
	case PERF_EVENT_IOC_DISABLE:
		func = _perf_event_disable;
		break;
	case PERF_EVENT_IOC_RESET:
		func = _perf_event_reset;
		break;

	case PERF_EVENT_IOC_REFRESH:
		return _perf_event_refresh(event, arg);

	case PERF_EVENT_IOC_PERIOD:
	{
		u64 value;

		if (copy_from_user(&value, (u64 __user *)arg, sizeof(value)))
			return -EFAULT;

		return _perf_event_period(event, value);
	}
	case PERF_EVENT_IOC_ID:
	{
		u64 id = primary_event_id(event);

		if (copy_to_user((void __user *)arg, &id, sizeof(id)))
			return -EFAULT;
		return 0;
	}

	case PERF_EVENT_IOC_SET_OUTPUT:
	{
		int ret;
		if (arg != -1) {
			struct perf_event *output_event;
			struct fd output;
			ret = perf_fget_light(arg, &output);
			if (ret)
				return ret;
			output_event = output.file->private_data;
			ret = perf_event_set_output(event, output_event);
			fdput(output);
		} else {
			ret = perf_event_set_output(event, NULL);
		}
		return ret;
	}

	case PERF_EVENT_IOC_SET_FILTER:
		return perf_event_set_filter(event, (void __user *)arg);

	case PERF_EVENT_IOC_SET_BPF:
	{
		struct bpf_prog *prog;
		int err;

		prog = bpf_prog_get(arg);
		if (IS_ERR(prog))
			return PTR_ERR(prog);

		err = perf_event_set_bpf_prog(event, prog, 0);
		if (err) {
			bpf_prog_put(prog);
			return err;
		}

		return 0;
	}

	case PERF_EVENT_IOC_PAUSE_OUTPUT: {
		struct perf_buffer *rb;

		rcu_read_lock();
		rb = rcu_dereference(event->rb);
		if (!rb || !rb->nr_pages) {
			rcu_read_unlock();
			return -EINVAL;
		}
		rb_toggle_paused(rb, !!arg);
		rcu_read_unlock();
		return 0;
	}

	case PERF_EVENT_IOC_QUERY_BPF:
		return perf_event_query_prog_array(event, (void __user *)arg);

	case PERF_EVENT_IOC_MODIFY_ATTRIBUTES: {
		struct perf_event_attr new_attr;
		int err = perf_copy_attr((struct perf_event_attr __user *)arg,
					 &new_attr);

		if (err)
			return err;

		return perf_event_modify_attr(event,  &new_attr);
	}
	default:
		return -ENOTTY;
	}

	if (flags & PERF_IOC_FLAG_GROUP)
		perf_event_for_each(event, func);
	else
		perf_event_for_each_child(event, func);

	return 0;
}

static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	struct perf_event *event = file->private_data;
	struct perf_event_context *ctx;
	long ret;

	/* Treat ioctl like writes as it is likely a mutating operation. */
	ret = security_perf_event_write(event);
	if (ret)
		return ret;

	ctx = perf_event_ctx_lock(event);
	ret = _perf_ioctl(event, cmd, arg);
	perf_event_ctx_unlock(event, ctx);

	return ret;
}

#ifdef CONFIG_COMPAT
static long perf_compat_ioctl(struct file *file, unsigned int cmd,
				unsigned long arg)
{
	switch (_IOC_NR(cmd)) {
	case _IOC_NR(PERF_EVENT_IOC_SET_FILTER):
	case _IOC_NR(PERF_EVENT_IOC_ID):
	case _IOC_NR(PERF_EVENT_IOC_QUERY_BPF):
	case _IOC_NR(PERF_EVENT_IOC_MODIFY_ATTRIBUTES):
		/* Fix up pointer size (usually 4 -> 8 in 32-on-64-bit case */
		if (_IOC_SIZE(cmd) == sizeof(compat_uptr_t)) {
			cmd &= ~IOCSIZE_MASK;
			cmd |= sizeof(void *) << IOCSIZE_SHIFT;
		}
		break;
	}
	return perf_ioctl(file, cmd, arg);
}
#else
# define perf_compat_ioctl NULL
#endif

int perf_event_task_enable(void)
{
	struct perf_event_context *ctx;
	struct perf_event *event;

	mutex_lock(&current->perf_event_mutex);
	list_for_each_entry(event, &current->perf_event_list, owner_entry) {
		ctx = perf_event_ctx_lock(event);
		perf_event_for_each_child(event, _perf_event_enable);
		perf_event_ctx_unlock(event, ctx);
	}
	mutex_unlock(&current->perf_event_mutex);

	return 0;
}

int perf_event_task_disable(void)
{
	struct perf_event_context *ctx;
	struct perf_event *event;

	mutex_lock(&current->perf_event_mutex);
	list_for_each_entry(event, &current->perf_event_list, owner_entry) {
		ctx = perf_event_ctx_lock(event);
		perf_event_for_each_child(event, _perf_event_disable);
		perf_event_ctx_unlock(event, ctx);
	}
	mutex_unlock(&current->perf_event_mutex);

	return 0;
}

static int perf_event_index(struct perf_event *event)
{
	if (event->hw.state & PERF_HES_STOPPED)
		return 0;

	if (event->state != PERF_EVENT_STATE_ACTIVE)
		return 0;

	return event->pmu->event_idx(event);
}

static void perf_event_init_userpage(struct perf_event *event)
{
	struct perf_event_mmap_page *userpg;
	struct perf_buffer *rb;

	rcu_read_lock();
	rb = rcu_dereference(event->rb);
	if (!rb)
		goto unlock;

	userpg = rb->user_page;

	/* Allow new userspace to detect that bit 0 is deprecated */
	userpg->cap_bit0_is_deprecated = 1;
	userpg->size = offsetof(struct perf_event_mmap_page, __reserved);
	userpg->data_offset = PAGE_SIZE;
	userpg->data_size = perf_data_size(rb);

unlock:
	rcu_read_unlock();
}

void __weak arch_perf_update_userpage(
	struct perf_event *event, struct perf_event_mmap_page *userpg, u64 now)
{
}

/*
 * Callers need to ensure there can be no nesting of this function, otherwise
 * the seqlock logic goes bad. We can not serialize this because the arch
 * code calls this from NMI context.
 */
void perf_event_update_userpage(struct perf_event *event)
{
	struct perf_event_mmap_page *userpg;
	struct perf_buffer *rb;
	u64 enabled, running, now;

	rcu_read_lock();
	rb = rcu_dereference(event->rb);
	if (!rb)
		goto unlock;

	/*
	 * compute total_time_enabled, total_time_running
	 * based on snapshot values taken when the event
	 * was last scheduled in.
	 *
	 * we cannot simply called update_context_time()
	 * because of locking issue as we can be called in
	 * NMI context
	 */
	calc_timer_values(event, &now, &enabled, &running);

	userpg = rb->user_page;
	/*
	 * Disable preemption to guarantee consistent time stamps are stored to
	 * the user page.
	 */
	preempt_disable();
	++userpg->lock;
	barrier();
	userpg->index = perf_event_index(event);
	userpg->offset = perf_event_count(event);
	if (userpg->index)
		userpg->offset -= local64_read(&event->hw.prev_count);

	userpg->time_enabled = enabled +
			atomic64_read(&event->child_total_time_enabled);

	userpg->time_running = running +
			atomic64_read(&event->child_total_time_running);

	arch_perf_update_userpage(event, userpg, now);

	barrier();
	++userpg->lock;
	preempt_enable();
unlock:
	rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(perf_event_update_userpage);

static vm_fault_t perf_mmap_fault(struct vm_fault *vmf)
{
	struct perf_event *event = vmf->vma->vm_file->private_data;
	struct perf_buffer *rb;
	vm_fault_t ret = VM_FAULT_SIGBUS;

	if (vmf->flags & FAULT_FLAG_MKWRITE) {
		if (vmf->pgoff == 0)
			ret = 0;
		return ret;
	}

	rcu_read_lock();
	rb = rcu_dereference(event->rb);
	if (!rb)
		goto unlock;

	if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
		goto unlock;

	vmf->page = perf_mmap_to_page(rb, vmf->pgoff);
	if (!vmf->page)
		goto unlock;

	get_page(vmf->page);
	vmf->page->mapping = vmf->vma->vm_file->f_mapping;
	vmf->page->index   = vmf->pgoff;

	ret = 0;
unlock:
	rcu_read_unlock();

	return ret;
}

static void ring_buffer_attach(struct perf_event *event,
			       struct perf_buffer *rb)
{
	struct perf_buffer *old_rb = NULL;
	unsigned long flags;

	WARN_ON_ONCE(event->parent);

	if (event->rb) {
		/*
		 * Should be impossible, we set this when removing
		 * event->rb_entry and wait/clear when adding event->rb_entry.
		 */
		WARN_ON_ONCE(event->rcu_pending);

		old_rb = event->rb;
		spin_lock_irqsave(&old_rb->event_lock, flags);
		list_del_rcu(&event->rb_entry);
		spin_unlock_irqrestore(&old_rb->event_lock, flags);

		event->rcu_batches = get_state_synchronize_rcu();
		event->rcu_pending = 1;
	}

	if (rb) {
		if (event->rcu_pending) {
			cond_synchronize_rcu(event->rcu_batches);
			event->rcu_pending = 0;
		}

		spin_lock_irqsave(&rb->event_lock, flags);
		list_add_rcu(&event->rb_entry, &rb->event_list);
		spin_unlock_irqrestore(&rb->event_lock, flags);
	}

	/*
	 * Avoid racing with perf_mmap_close(AUX): stop the event
	 * before swizzling the event::rb pointer; if it's getting
	 * unmapped, its aux_mmap_count will be 0 and it won't
	 * restart. See the comment in __perf_pmu_output_stop().
	 *
	 * Data will inevitably be lost when set_output is done in
	 * mid-air, but then again, whoever does it like this is
	 * not in for the data anyway.
	 */
	if (has_aux(event))
		perf_event_stop(event, 0);

	rcu_assign_pointer(event->rb, rb);

	if (old_rb) {
		ring_buffer_put(old_rb);
		/*
		 * Since we detached before setting the new rb, so that we
		 * could attach the new rb, we could have missed a wakeup.
		 * Provide it now.
		 */
		wake_up_all(&event->waitq);
	}
}

static void ring_buffer_wakeup(struct perf_event *event)
{
	struct perf_buffer *rb;

	if (event->parent)
		event = event->parent;

	rcu_read_lock();
	rb = rcu_dereference(event->rb);
	if (rb) {
		list_for_each_entry_rcu(event, &rb->event_list, rb_entry)
			wake_up_all(&event->waitq);
	}
	rcu_read_unlock();
}

struct perf_buffer *ring_buffer_get(struct perf_event *event)
{
	struct perf_buffer *rb;

	if (event->parent)
		event = event->parent;

	rcu_read_lock();
	rb = rcu_dereference(event->rb);
	if (rb) {
		if (!refcount_inc_not_zero(&rb->refcount))
			rb = NULL;
	}
	rcu_read_unlock();

	return rb;
}

void ring_buffer_put(struct perf_buffer *rb)
{
	if (!refcount_dec_and_test(&rb->refcount))
		return;

	WARN_ON_ONCE(!list_empty(&rb->event_list));

	call_rcu(&rb->rcu_head, rb_free_rcu);
}

static void perf_mmap_open(struct vm_area_struct *vma)
{
	struct perf_event *event = vma->vm_file->private_data;

	atomic_inc(&event->mmap_count);
	atomic_inc(&event->rb->mmap_count);

	if (vma->vm_pgoff)
		atomic_inc(&event->rb->aux_mmap_count);

	if (event->pmu->event_mapped)
		event->pmu->event_mapped(event, vma->vm_mm);
}

static void perf_pmu_output_stop(struct perf_event *event);

/*
 * A buffer can be mmap()ed multiple times; either directly through the same
 * event, or through other events by use of perf_event_set_output().
 *
 * In order to undo the VM accounting done by perf_mmap() we need to destroy
 * the buffer here, where we still have a VM context. This means we need
 * to detach all events redirecting to us.
 */
static void perf_mmap_close(struct vm_area_struct *vma)
{
	struct perf_event *event = vma->vm_file->private_data;
	struct perf_buffer *rb = ring_buffer_get(event);
	struct user_struct *mmap_user = rb->mmap_user;
	int mmap_locked = rb->mmap_locked;
	unsigned long size = perf_data_size(rb);
	bool detach_rest = false;

	if (event->pmu->event_unmapped)
		event->pmu->event_unmapped(event, vma->vm_mm);

	/*
	 * rb->aux_mmap_count will always drop before rb->mmap_count and
	 * event->mmap_count, so it is ok to use event->mmap_mutex to
	 * serialize with perf_mmap here.
	 */
	if (rb_has_aux(rb) && vma->vm_pgoff == rb->aux_pgoff &&
	    atomic_dec_and_mutex_lock(&rb->aux_mmap_count, &event->mmap_mutex)) {
		/*
		 * Stop all AUX events that are writing to this buffer,
		 * so that we can free its AUX pages and corresponding PMU
		 * data. Note that after rb::aux_mmap_count dropped to zero,
		 * they won't start any more (see perf_aux_output_begin()).
		 */
		perf_pmu_output_stop(event);

		/* now it's safe to free the pages */
		atomic_long_sub(rb->aux_nr_pages - rb->aux_mmap_locked, &mmap_user->locked_vm);
		atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm);

		/* this has to be the last one */
		rb_free_aux(rb);
		WARN_ON_ONCE(refcount_read(&rb->aux_refcount));

		mutex_unlock(&event->mmap_mutex);
	}

	if (atomic_dec_and_test(&rb->mmap_count))
		detach_rest = true;

	if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex))
		goto out_put;

	ring_buffer_attach(event, NULL);
	mutex_unlock(&event->mmap_mutex);

	/* If there's still other mmap()s of this buffer, we're done. */
	if (!detach_rest)
		goto out_put;

	/*
	 * No other mmap()s, detach from all other events that might redirect
	 * into the now unreachable buffer. Somewhat complicated by the
	 * fact that rb::event_lock otherwise nests inside mmap_mutex.
	 */
again:
	rcu_read_lock();
	list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
		if (!atomic_long_inc_not_zero(&event->refcount)) {
			/*
			 * This event is en-route to free_event() which will
			 * detach it and remove it from the list.
			 */
			continue;
		}
		rcu_read_unlock();

		mutex_lock(&event->mmap_mutex);
		/*
		 * Check we didn't race with perf_event_set_output() which can
		 * swizzle the rb from under us while we were waiting to
		 * acquire mmap_mutex.
		 *
		 * If we find a different rb; ignore this event, a next
		 * iteration will no longer find it on the list. We have to
		 * still restart the iteration to make sure we're not now
		 * iterating the wrong list.
		 */
		if (event->rb == rb)
			ring_buffer_attach(event, NULL);

		mutex_unlock(&event->mmap_mutex);
		put_event(event);

		/*
		 * Restart the iteration; either we're on the wrong list or
		 * destroyed its integrity by doing a deletion.
		 */
		goto again;
	}
	rcu_read_unlock();

	/*
	 * It could be there's still a few 0-ref events on the list; they'll
	 * get cleaned up by free_event() -- they'll also still have their
	 * ref on the rb and will free it whenever they are done with it.
	 *
	 * Aside from that, this buffer is 'fully' detached and unmapped,
	 * undo the VM accounting.
	 */

	atomic_long_sub((size >> PAGE_SHIFT) + 1 - mmap_locked,
			&mmap_user->locked_vm);
	atomic64_sub(mmap_locked, &vma->vm_mm->pinned_vm);
	free_uid(mmap_user);

out_put:
	ring_buffer_put(rb); /* could be last */
}

static const struct vm_operations_struct perf_mmap_vmops = {
	.open		= perf_mmap_open,
	.close		= perf_mmap_close, /* non mergeable */
	.fault		= perf_mmap_fault,
	.page_mkwrite	= perf_mmap_fault,
};

static int perf_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct perf_event *event = file->private_data;
	unsigned long user_locked, user_lock_limit;
	struct user_struct *user = current_user();
	struct perf_buffer *rb = NULL;
	unsigned long locked, lock_limit;
	unsigned long vma_size;
	unsigned long nr_pages;
	long user_extra = 0, extra = 0;
	int ret = 0, flags = 0;

	/*
	 * Don't allow mmap() of inherited per-task counters. This would
	 * create a performance issue due to all children writing to the
	 * same rb.
	 */
	if (event->cpu == -1 && event->attr.inherit)
		return -EINVAL;

	if (!(vma->vm_flags & VM_SHARED))
		return -EINVAL;

	ret = security_perf_event_read(event);
	if (ret)
		return ret;

	vma_size = vma->vm_end - vma->vm_start;

	if (vma->vm_pgoff == 0) {
		nr_pages = (vma_size / PAGE_SIZE) - 1;
	} else {
		/*
		 * AUX area mapping: if rb->aux_nr_pages != 0, it's already
		 * mapped, all subsequent mappings should have the same size
		 * and offset. Must be above the normal perf buffer.
		 */
		u64 aux_offset, aux_size;

		if (!<