1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * Copyright (C) 2010 Red Hat, Inc., Peter Zijlstra 4 * 5 * Provides a framework for enqueueing and running callbacks from hardirq 6 * context. The enqueueing is NMI-safe. 7 */ 8 9#include <linux/bug.h> 10#include <linux/kernel.h> 11#include <linux/export.h> 12#include <linux/irq_work.h> 13#include <linux/percpu.h> 14#include <linux/hardirq.h> 15#include <linux/irqflags.h> 16#include <linux/sched.h> 17#include <linux/tick.h> 18#include <linux/cpu.h> 19#include <linux/notifier.h> 20#include <linux/smp.h> 21#include <linux/smpboot.h> 22#include <asm/processor.h> 23#include <linux/kasan.h> 24 25#include <trace/events/ipi.h> 26 27static DEFINE_PER_CPU(struct llist_head, raised_list); 28static DEFINE_PER_CPU(struct llist_head, lazy_list); 29static DEFINE_PER_CPU(struct task_struct *, irq_workd); 30 31static void wake_irq_workd(void) 32{ 33 struct task_struct *tsk = __this_cpu_read(irq_workd); 34 35 if (!llist_empty(this_cpu_ptr(&lazy_list)) && tsk) 36 wake_up_process(tsk); 37} 38 39#ifdef CONFIG_SMP 40static void irq_work_wake(struct irq_work *entry) 41{ 42 wake_irq_workd(); 43} 44 45static DEFINE_PER_CPU(struct irq_work, irq_work_wakeup) = 46 IRQ_WORK_INIT_HARD(irq_work_wake); 47#endif 48 49static int irq_workd_should_run(unsigned int cpu) 50{ 51 return !llist_empty(this_cpu_ptr(&lazy_list)); 52} 53 54/* 55 * Claim the entry so that no one else will poke at it. 56 */ 57static bool irq_work_claim(struct irq_work *work) 58{ 59 int oflags; 60 61 oflags = atomic_fetch_or(IRQ_WORK_CLAIMED | CSD_TYPE_IRQ_WORK, &work->node.a_flags); 62 /* 63 * If the work is already pending, no need to raise the IPI. 64 * The pairing smp_mb() in irq_work_single() makes sure 65 * everything we did before is visible. 66 */ 67 if (oflags & IRQ_WORK_PENDING) 68 return false; 69 return true; 70} 71 72void __weak arch_irq_work_raise(void) 73{ 74 /* 75 * Lame architectures will get the timer tick callback 76 */ 77} 78 79static __always_inline void irq_work_raise(struct irq_work *work) 80{ 81 if (trace_ipi_send_cpu_enabled() && arch_irq_work_has_interrupt()) 82 trace_ipi_send_cpu(smp_processor_id(), _RET_IP_, work->func); 83 84 arch_irq_work_raise(); 85} 86 87/* Enqueue on current CPU, work must already be claimed and preempt disabled */ 88static void __irq_work_queue_local(struct irq_work *work) 89{ 90 struct llist_head *list; 91 bool rt_lazy_work = false; 92 bool lazy_work = false; 93 int work_flags; 94 95 work_flags = atomic_read(&work->node.a_flags); 96 if (work_flags & IRQ_WORK_LAZY) 97 lazy_work = true; 98 else if (IS_ENABLED(CONFIG_PREEMPT_RT) && 99 !(work_flags & IRQ_WORK_HARD_IRQ)) 100 rt_lazy_work = true; 101 102 if (lazy_work || rt_lazy_work) 103 list = this_cpu_ptr(&lazy_list); 104 else 105 list = this_cpu_ptr(&raised_list); 106 107 if (!llist_add(&work->node.llist, list)) 108 return; 109 110 /* If the work is "lazy", handle it from next tick if any */ 111 if (!lazy_work || tick_nohz_tick_stopped()) 112 irq_work_raise(work); 113} 114 115/* Enqueue the irq work @work on the current CPU */ 116bool irq_work_queue(struct irq_work *work) 117{ 118 /* Only queue if not already pending */ 119 if (!irq_work_claim(work)) 120 return false; 121 122 /* Queue the entry and raise the IPI if needed. */ 123 preempt_disable(); 124 __irq_work_queue_local(work); 125 preempt_enable(); 126 127 return true; 128} 129EXPORT_SYMBOL_GPL(irq_work_queue); 130 131/* 132 * Enqueue the irq_work @work on @cpu unless it's already pending 133 * somewhere. 134 * 135 * Can be re-enqueued while the callback is still in progress. 136 */ 137bool irq_work_queue_on(struct irq_work *work, int cpu) 138{ 139#ifndef CONFIG_SMP 140 return irq_work_queue(work); 141 142#else /* CONFIG_SMP: */ 143 /* All work should have been flushed before going offline */ 144 WARN_ON_ONCE(cpu_is_offline(cpu)); 145 146 /* Only queue if not already pending */ 147 if (!irq_work_claim(work)) 148 return false; 149 150 kasan_record_aux_stack_noalloc(work); 151 152 preempt_disable(); 153 if (cpu != smp_processor_id()) { 154 /* Arch remote IPI send/receive backend aren't NMI safe */ 155 WARN_ON_ONCE(in_nmi()); 156 157 /* 158 * On PREEMPT_RT the items which are not marked as 159 * IRQ_WORK_HARD_IRQ are added to the lazy list and a HARD work 160 * item is used on the remote CPU to wake the thread. 161 */ 162 if (IS_ENABLED(CONFIG_PREEMPT_RT) && 163 !(atomic_read(&work->node.a_flags) & IRQ_WORK_HARD_IRQ)) { 164 165 if (!llist_add(&work->node.llist, &per_cpu(lazy_list, cpu))) 166 goto out; 167 168 work = &per_cpu(irq_work_wakeup, cpu); 169 if (!irq_work_claim(work)) 170 goto out; 171 } 172 173 __smp_call_single_queue(cpu, &work->node.llist); 174 } else { 175 __irq_work_queue_local(work); 176 } 177out: 178 preempt_enable(); 179 180 return true; 181#endif /* CONFIG_SMP */ 182} 183 184bool irq_work_needs_cpu(void) 185{ 186 struct llist_head *raised, *lazy; 187 188 raised = this_cpu_ptr(&raised_list); 189 lazy = this_cpu_ptr(&lazy_list); 190 191 if (llist_empty(raised) || arch_irq_work_has_interrupt()) 192 if (llist_empty(lazy)) 193 return false; 194 195 /* All work should have been flushed before going offline */ 196 WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); 197 198 return true; 199} 200 201void irq_work_single(void *arg) 202{ 203 struct irq_work *work = arg; 204 int flags; 205 206 /* 207 * Clear the PENDING bit, after this point the @work can be re-used. 208 * The PENDING bit acts as a lock, and we own it, so we can clear it 209 * without atomic ops. 210 */ 211 flags = atomic_read(&work->node.a_flags); 212 flags &= ~IRQ_WORK_PENDING; 213 atomic_set(&work->node.a_flags, flags); 214 215 /* 216 * See irq_work_claim(). 217 */ 218 smp_mb(); 219 220 lockdep_irq_work_enter(flags); 221 work->func(work); 222 lockdep_irq_work_exit(flags); 223 224 /* 225 * Clear the BUSY bit, if set, and return to the free state if no-one 226 * else claimed it meanwhile. 227 */ 228 (void)atomic_cmpxchg(&work->node.a_flags, flags, flags & ~IRQ_WORK_BUSY); 229 230 if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) || 231 !arch_irq_work_has_interrupt()) 232 rcuwait_wake_up(&work->irqwait); 233} 234 235static void irq_work_run_list(struct llist_head *list) 236{ 237 struct irq_work *work, *tmp; 238 struct llist_node *llnode; 239 240 /* 241 * On PREEMPT_RT IRQ-work which is not marked as HARD will be processed 242 * in a per-CPU thread in preemptible context. Only the items which are 243 * marked as IRQ_WORK_HARD_IRQ will be processed in hardirq context. 244 */ 245 BUG_ON(!irqs_disabled() && !IS_ENABLED(CONFIG_PREEMPT_RT)); 246 247 if (llist_empty(list)) 248 return; 249 250 llnode = llist_del_all(list); 251 llist_for_each_entry_safe(work, tmp, llnode, node.llist) 252 irq_work_single(work); 253} 254 255/* 256 * hotplug calls this through: 257 * hotplug_cfd() -> flush_smp_call_function_queue() 258 */ 259void irq_work_run(void) 260{ 261 irq_work_run_list(this_cpu_ptr(&raised_list)); 262 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) 263 irq_work_run_list(this_cpu_ptr(&lazy_list)); 264 else 265 wake_irq_workd(); 266} 267EXPORT_SYMBOL_GPL(irq_work_run); 268 269void irq_work_tick(void) 270{ 271 struct llist_head *raised = this_cpu_ptr(&raised_list); 272 273 if (!llist_empty(raised) && !arch_irq_work_has_interrupt()) 274 irq_work_run_list(raised); 275 276 if (!IS_ENABLED(CONFIG_PREEMPT_RT)) 277 irq_work_run_list(this_cpu_ptr(&lazy_list)); 278 else 279 wake_irq_workd(); 280} 281 282/* 283 * Synchronize against the irq_work @entry, ensures the entry is not 284 * currently in use. 285 */ 286void irq_work_sync(struct irq_work *work) 287{ 288 lockdep_assert_irqs_enabled(); 289 might_sleep(); 290 291 if ((IS_ENABLED(CONFIG_PREEMPT_RT) && !irq_work_is_hard(work)) || 292 !arch_irq_work_has_interrupt()) { 293 rcuwait_wait_event(&work->irqwait, !irq_work_is_busy(work), 294 TASK_UNINTERRUPTIBLE); 295 return; 296 } 297 298 while (irq_work_is_busy(work)) 299 cpu_relax(); 300} 301EXPORT_SYMBOL_GPL(irq_work_sync); 302 303static void run_irq_workd(unsigned int cpu) 304{ 305 irq_work_run_list(this_cpu_ptr(&lazy_list)); 306} 307 308static void irq_workd_setup(unsigned int cpu) 309{ 310 sched_set_fifo_low(current); 311} 312 313static struct smp_hotplug_thread irqwork_threads = { 314 .store = &irq_workd, 315 .setup = irq_workd_setup, 316 .thread_should_run = irq_workd_should_run, 317 .thread_fn = run_irq_workd, 318 .thread_comm = "irq_work/%u", 319}; 320 321static __init int irq_work_init_threads(void) 322{ 323 if (IS_ENABLED(CONFIG_PREEMPT_RT)) 324 BUG_ON(smpboot_register_percpu_thread(&irqwork_threads)); 325 return 0; 326} 327early_initcall(irq_work_init_threads); 328