cpufreq: governor: Free dbs_data directly when gov->init() fails

Due to the kobject embedded in the dbs_data doest not has a release()
method yet, it needs to use kfree() to free dbs_data directly when
governor fails to allocate the tunner field of dbs_data.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Use kobject release() method to free dbs_data

The struct dbs_data embeds a struct gov_attr_set and
the struct gov_attr_set embeds a kobject. Since every kobject must have
a release() method and we can't use kfree() to free it directly,
so introduce cpufreq_dbs_data_release() to release the dbs_data via
the kobject::release() method. This fixes the calltrace like below:

ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x34
WARNING: CPU: 12 PID: 810 at lib/debugobjects.c:505 debug_print_object+0xb8/0x100
Modules linked in:
CPU: 12 PID: 810 Comm: sh Not tainted 5.16.0-next-20220120-yocto-standard+ #536
Hardware name: Marvell OcteonTX CN96XX board (DT)
pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : debug_print_object+0xb8/0x100
lr : debug_print_object+0xb8/0x100
sp : ffff80001dfcf9a0
x29: ffff80001dfcf9a0 x28: 0000000000000001 x27: ffff0001464f0000
x26: 0000000000000000 x25: ffff8000090e3f00 x24: ffff80000af60210
x23: ffff8000094dfb78 x22: ffff8000090e3f00 x21: ffff0001080b7118
x20: ffff80000aeb2430 x19: ffff800009e8f5e0 x18: 0000000000000000
x17: 0000000000000002 x16: 00004d62e58be040 x15: 013590470523aff8
x14: ffff8000090e1828 x13: 0000000001359047 x12: 00000000f5257d14
x11: 0000000000040591 x10: 0000000066c1ffea x9 : ffff8000080d15e0
x8 : ffff80000a1765a8 x7 : 0000000000000000 x6 : 0000000000000001
x5 : ffff800009e8c000 x4 : ffff800009e8c760 x3 : 0000000000000000
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0001474ed040
Call trace:
debug_print_object+0xb8/0x100
__debug_check_no_obj_freed+0x1d0/0x25c
debug_check_no_obj_freed+0x24/0xa0
kfree+0x11c/0x440
cpufreq_dbs_governor_exit+0xa8/0xac
cpufreq_exit_governor+0x44/0x90
cpufreq_set_policy+0x29c/0x570
store_scaling_governor+0x110/0x154
store+0xb0/0xe0
sysfs_kf_write+0x58/0x84
kernfs_fop_write_iter+0x12c/0x1c0
new_sync_write+0xf0/0x18c
vfs_write+0x1cc/0x220
ksys_write+0x74/0x100
__arm64_sys_write+0x28/0x3c
invoke_syscall.constprop.0+0x58/0xf0
do_el0_svc+0x70/0x170
el0_svc+0x54/0x190
el0t_64_sync_handler+0xa4/0x130
el0t_64_sync+0x1a0/0x1a4
irq event stamp: 189006
hardirqs last enabled at (189005): [<ffff8000080849d0>] finish_task_switch.isra.0+0xe0/0x2c0
hardirqs last disabled at (189006): [<ffff8000090667a4>] el1_dbg+0x24/0xa0
softirqs last enabled at (188966): [<ffff8000080106d0>] __do_softirq+0x4b0/0x6a0
softirqs last disabled at (188957): [<ffff80000804a618>] __irq_exit_rcu+0x108/0x1a4

[ rjw: Because can be freed by the gov_attr_set_put() in
cpufreq_dbs_governor_exit() now, it is also necessary to put the
invocation of the governor ->exit() callback into the new
cpufreq_dbs_data_release() function. ]

Fixes: c4435630361d ("cpufreq: governor: New sysfs show/store callbacks for governor tunables")
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: unify show() and store() naming and use __ATTR_XX

Usually, sysfs attributes have .show and .store and their naming
convention is filename_show() and filename_store().

But in cpufreq the naming convention of these functions is
show_filename() and store_filename() which prevents __ATTR_RW() and
__ATTR_RO() from being used in there to simplify code.

Accordingly, change the naming convention of the sysfs .show and
.store methods in cpufreq to follow the one expected by __ATTR_RW()
and __ATTR_RO() and use these macros in that code.

Signed-off-by: Lianjie Zhang <zhanglianjie@uniontech.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: cpufreq_governor: Demote store_sampling_rate() header to standard comment block

There is no need for this to be denoted as kerneldoc.

Fixes the following W=1 kernel build warning(s):

drivers/cpufreq/cpufreq_governor.c:46: warning: Function parameter or member 'attr_set' not described in 'store_sampling_rate'
drivers/cpufreq/cpufreq_governor.c:46: warning: Function parameter or member 'buf' not described in 'store_sampling_rate'
drivers/cpufreq/cpufreq_governor.c:46: warning: Function parameter or member 'count' not described in 'store_sampling_rate'

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Use vtime aware kcpustat accessors for user time

We can now safely read user and guest kcpustat fields on nohz_full CPUs.
Use the appropriate accessors.

Reported-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Link: https://lkml.kernel.org/r/20191121024430.19938-5-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

Based on 2 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

cpufreq: Fix kobject memleak

Currently the error return path from kobject_init_and_add() is not
followed by a call to kobject_put() - which means we are leaking the
kobject.

Fix it by adding a call to kobject_put() in the error path of
kobject_init_and_add().

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Tobin C. Harding <tobin@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq/cpufreq_governor: Replace synchronize_sched() with synchronize_rcu()

Now that synchronize_rcu() waits for preempt-disable regions of code
as well as RCU read-side critical sections, synchronize_sched() can be
replaced by synchronize_rcu(). This commit therefore makes this change.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

cpufreq: governor: Avoid accessing invalid governor_data

If cppc_cpufreq.ko is deleted at the same time that tuned-adm is
changing profiles, there is a small chance that a race can occur
between cpufreq_dbs_governor_exit() and cpufreq_dbs_governor_limits()
resulting in a system failure when the latter tries to use
policy->governor_data that has been freed by the former.

This patch uses gov_dbs_data_mutex to synchronize access.

Fixes: e788892ba3cc (cpufreq: governor: Get rid of governor events)
Signed-off-by: Henry Willard <henry.willard@oracle.com>
[ rjw: Subject, minor white space adjustment ]
Cc: 4.8+ <stable@vger.kernel.org> # 4.8+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Fix long idle detection logic in load calculation

According to current code implementation, detecting the long
idle period is done by checking if the interval between two
adjacent utilization update handlers is long enough. Although
this mechanism can detect if the idle period is long enough
(no utilization hooks invoked during idle period), it might
not cover a corner case: if the task has occupied the CPU
for too long which causes no context switches during that
period, then no utilization handler will be launched until this
high prio task is scheduled out. As a result, the idle_periods
field might be calculated incorrectly because it regards the
100% load as 0% and makes the conservative governor who uses
this field confusing.

Change the detection to compare the idle_time with sampling_rate
directly.

Reported-by: Artem S. Tashkinov <t.artem@mailcity.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Rename cpufreq_can_do_remote_dvfs()

This routine checks if the CPU running this code belongs to the policy
of the target CPU or if not, can it do remote DVFS for it remotely. But
the current name of it implies as if it is only about doing remote
updates.

Rename it to make it more relevant.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Ensure sufficiently large sampling intervals

After commit aa7519af450d (cpufreq: Use transition_delay_us for legacy
governors as well) the sampling_rate field of struct dbs_data may be
less than the tick period which causes dbs_update() to produce
incorrect results, so make the code ensure that the value of that
field will always be sufficiently large.

Fixes: aa7519af450d (cpufreq: Use transition_delay_us for legacy governors as well)
Reported-by: Andy Tang <andy.tang@nxp.com>
Reported-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Andy Tang <andy.tang@nxp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

sched: cpufreq: Allow remote cpufreq callbacks

With Android UI and benchmarks the latency of cpufreq response to
certain scheduling events can become very critical. Currently, callbacks
into cpufreq governors are only made from the scheduler if the target
CPU of the event is the same as the current CPU. This means there are
certain situations where a target CPU may not run the cpufreq governor
for some time.

One testcase to show this behavior is where a task starts running on
CPU0, then a new task is also spawned on CPU0 by a task on CPU1. If the
system is configured such that the new tasks should receive maximum
demand initially, this should result in CPU0 increasing frequency
immediately. But because of the above mentioned limitation though, this
does not occur.

This patch updates the scheduler core to call the cpufreq callbacks for
remote CPUs as well.

The schedutil, ondemand and conservative governors are updated to
process cpufreq utilization update hooks called for remote CPUs where
the remote CPU is managed by the cpufreq policy of the local CPU.

The intel_pstate driver is updated to always reject remote callbacks.

This is tested with couple of usecases (Android: hackbench, recentfling,
galleryfling, vellamo, Ubuntu: hackbench) on ARM hikey board (64 bit
octa-core, single policy). Only galleryfling showed minor improvements,
while others didn't had much deviation.

The reason being that this patch only targets a corner case, where
following are required to be true to improve performance and that
doesn't happen too often with these tests:

- Task is migrated to another CPU.
- The task has high demand, and should take the target CPU to higher
OPPs.
- And the target CPU doesn't call into the cpufreq governor until the
next tick.

Based on initial work from Steve Muckle.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Use transition_delay_us for legacy governors as well

The policy->transition_delay_us field is used only by the schedutil
governor currently, and this field describes how fast the driver wants
the cpufreq governor to change CPUs frequency. It should rather be a
common thing across all governors, as it doesn't have any schedutil
dependency here.

Create a new helper cpufreq_policy_transition_delay_us() to get the
transition delay across all governors.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Drop min_sampling_rate

The cpufreq core and governors aren't supposed to set a limit on how
fast we want to try changing the frequency. This is currently done for
the legacy governors with help of min_sampling_rate.

At worst, we may end up setting the sampling rate to a value lower than
the rate at which frequency can be changed and then one of the CPUs in
the policy will be only changing frequency for ever.

But that is something for the user to decide and there is no need to
have special handling for such cases in the core. Leave it for the user
to figure out.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/cpufreq.h>

We are going to split <linux/sched/cpufreq.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/cpufreq.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

sched/cputime: Convert kcpustat to nsecs

Kernel CPU stats are stored in cputime_t which is an architecture
defined type, and hence a bit opaque and requiring accessors and mutators
for any operation.

Converting them to nsecs simplifies the code and is one step toward
the removal of cputime_t in the core code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

cpufreq: conservative: Decrease frequency faster for deferred updates

Conservative governor changes the CPU frequency in steps.
That means that if a CPU runs at max frequency, it will need several
sampling periods to return to min frequency when the workload
is finished.

If the update function that calculates the load and target frequency
is deferred, the governor might need even more time to decrease the
frequency.

This may have impact to power consumption and after all conservative
should decrease the frequency if there is no workload at every sampling
rate.

To resolve the above issue calculate the number of sampling periods
that the update is deferred. Considering that for each sampling period
conservative should drop the frequency by a freq_step because the
CPU was idle apply the proper subtraction to requested frequency.

Below, the kernel trace with and without this patch. First an
intensive workload is applied on a specific CPU. Then the workload
is removed and the CPU goes to idle.

WITHOUT

<idle>-0 [007] dN.. 620.329153: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 620.350857: cpu_frequency: state=1700000 cpu_id=7
kworker/7:2-556 [007] .... 620.370856: cpu_frequency: state=1900000 cpu_id=7
kworker/7:2-556 [007] .... 620.390854: cpu_frequency: state=2100000 cpu_id=7
kworker/7:2-556 [007] .... 620.411853: cpu_frequency: state=2200000 cpu_id=7
kworker/7:2-556 [007] .... 620.432854: cpu_frequency: state=2400000 cpu_id=7
kworker/7:2-556 [007] .... 620.453854: cpu_frequency: state=2600000 cpu_id=7
kworker/7:2-556 [007] .... 620.494856: cpu_frequency: state=2900000 cpu_id=7
kworker/7:2-556 [007] .... 620.515856: cpu_frequency: state=3100000 cpu_id=7
kworker/7:2-556 [007] .... 620.536858: cpu_frequency: state=3300000 cpu_id=7
kworker/7:2-556 [007] .... 620.557857: cpu_frequency: state=3401000 cpu_id=7
<idle>-0 [007] d... 669.591363: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 669.591939: cpu_idle: state=4294967295 cpu_id=7
<idle>-0 [007] d... 669.591980: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] dN.. 669.591989: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 670.201224: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 670.221975: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 670.222016: cpu_frequency: state=3300000 cpu_id=7
<idle>-0 [007] d... 670.222026: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 670.234964: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 670.801251: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 671.236046: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 671.236073: cpu_frequency: state=3100000 cpu_id=7
<idle>-0 [007] d... 671.236112: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 671.393437: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 671.401277: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 671.404083: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 671.404111: cpu_frequency: state=2900000 cpu_id=7
<idle>-0 [007] d... 671.404125: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 671.404974: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 671.501180: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 671.995414: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 671.995459: cpu_frequency: state=2800000 cpu_id=7
<idle>-0 [007] d... 671.995469: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 671.996287: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 672.001305: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.078374: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 672.078410: cpu_frequency: state=2600000 cpu_id=7
<idle>-0 [007] d... 672.078419: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.158020: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 672.158040: cpu_frequency: state=2400000 cpu_id=7
<idle>-0 [007] d... 672.158044: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.160038: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 672.234557: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.237121: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 672.237174: cpu_frequency: state=2100000 cpu_id=7
<idle>-0 [007] d... 672.237186: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.237778: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 672.267902: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.269860: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 672.269906: cpu_frequency: state=1900000 cpu_id=7
<idle>-0 [007] d... 672.269914: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.271902: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 672.751342: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 672.823056: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-556 [007] .... 672.823095: cpu_frequency: state=1600000 cpu_id=7

WITH

<idle>-0 [007] dN.. 4380.928009: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-399 [007] .... 4380.949767: cpu_frequency: state=2000000 cpu_id=7
kworker/7:2-399 [007] .... 4380.969765: cpu_frequency: state=2200000 cpu_id=7
kworker/7:2-399 [007] .... 4381.009766: cpu_frequency: state=2500000 cpu_id=7
kworker/7:2-399 [007] .... 4381.029767: cpu_frequency: state=2600000 cpu_id=7
kworker/7:2-399 [007] .... 4381.049769: cpu_frequency: state=2800000 cpu_id=7
kworker/7:2-399 [007] .... 4381.069769: cpu_frequency: state=3000000 cpu_id=7
kworker/7:2-399 [007] .... 4381.089771: cpu_frequency: state=3100000 cpu_id=7
kworker/7:2-399 [007] .... 4381.109772: cpu_frequency: state=3400000 cpu_id=7
kworker/7:2-399 [007] .... 4381.129773: cpu_frequency: state=3401000 cpu_id=7
<idle>-0 [007] d... 4428.226159: cpu_idle: state=1 cpu_id=7
<idle>-0 [007] d... 4428.226176: cpu_idle: state=4294967295 cpu_id=7
<idle>-0 [007] d... 4428.226181: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 4428.227177: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 4428.551640: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 4428.649239: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-399 [007] .... 4428.649268: cpu_frequency: state=2800000 cpu_id=7
<idle>-0 [007] d... 4428.649278: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 4428.689856: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 4428.799542: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 4428.801683: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-399 [007] .... 4428.801748: cpu_frequency: state=1700000 cpu_id=7
<idle>-0 [007] d... 4428.801761: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 4428.806545: cpu_idle: state=4294967295 cpu_id=7
...
<idle>-0 [007] d... 4429.051880: cpu_idle: state=4 cpu_id=7
<idle>-0 [007] d... 4429.086240: cpu_idle: state=4294967295 cpu_id=7
kworker/7:2-399 [007] .... 4429.086293: cpu_frequency: state=1600000 cpu_id=7

Without the patch the CPU dropped to min frequency after 3.2s
With the patch applied the CPU dropped to min frequency after 0.86s

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Don't use 'timer' keyword

The earlier implementation of governors used background timers and so
functions, mutex, etc had 'timer' keyword in their names.

But that's not true anymore. Replace 'timer' with 'update', as those
functions, variables are based around updates to frequency.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq / sched: Pass flags to cpufreq_update_util()

It is useful to know the reason why cpufreq_update_util() has just
been called and that can be passed as flags to cpufreq_update_util()
and to the ->func() callback in struct update_util_data. However,
doing that in addition to passing the util and max arguments they
already take would be clumsy, so avoid it.

Instead, use the observation that the schedutil governor is part
of the scheduler proper, so it can access scheduler data directly.
This allows the util and max arguments of cpufreq_update_util()
and the ->func() callback in struct update_util_data to be replaced
with a flags one, but schedutil has to be modified to follow.

Thus make the schedutil governor obtain the CFS utilization
information from the scheduler and use the "RT" and "DL" flags
instead of the special utilization value of ULONG_MAX to track
updates from the RT and DL sched classes. Make it non-modular
too to avoid having to export scheduler variables to modules at
large.

Next, update all of the other users of cpufreq_update_util()
and the ->func() callback in struct update_util_data accordingly.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Drop gov_cancel_work()

There's no reason for gov_cancel_work() to exist at all, as it only
has one caller and the only thing done by that caller is to invoke
gov_cancel_work().

Accordingly, drop gov_cancel_work() and move its contents to the
caller.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: Drop the 'initialized' field from struct cpufreq_governor

The 'initialized' field in struct cpufreq_governor is only used by
the conservative governor (as a usage counter) and the way that
happens is far from straightforward and arguably incorrect.

Namely, the value of 'initialized' is checked by
cpufreq_dbs_governor_init() and cpufreq_dbs_governor_exit() and
the results of those checks are passed (as the second argument) to
the ->init() and ->exit() callbacks in struct dbs_governor. Those
callbacks are only implemented by the ondemand and conservative
governors and ondemand doesn't use their second argument at all.
In turn, the conservative governor uses it to decide whether or not
to either register or unregister a transition notifier.

That whole mechanism is not only unnecessarily convoluted, but also
racy, because the 'initialized' field of struct cpufreq_governor is
updated in cpufreq_init_governor() and cpufreq_exit_governor() under
policy->rwsem which doesn't help if one of these functions is run
twice in parallel for different policies (which isn't impossible in
principle), for example.

Instead of it, add a proper usage counter to the conservative
governor and update it from cs_init() and cs_exit() which is
guaranteed to be non-racy, as those functions are only called
under gov_dbs_data_mutex which is global.

With that in place, drop the 'initialized' field from struct
cpufreq_governor as it is not used any more.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Create cpufreq_policy_apply_limits()

Create a new helper to avoid code duplication across governors.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Remove unnecessary bits from print message

pr_*() helpers already prefix the print messages with
"cpufreq_governor:" and similar details aren't required in the actual
message.

For example, the print message getting fixed looks like this before this
patch:

cpufreq_governor: cpufreq: Governor initialization failed (dbs_data kobject init error 0)

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Get rid of governor events

The design of the cpufreq governor API is not very straightforward,
as struct cpufreq_governor provides only one callback to be invoked
from different code paths for different purposes. The purpose it is
invoked for is determined by its second "event" argument, causing it
to act as a "callback multiplexer" of sorts.

Unfortunately, that leads to extra complexity in governors, some of
which implement the ->governor() callback as a switch statement
that simply checks the event argument and invokes a separate function
to handle that specific event.

That extra complexity can be eliminated by replacing the all-purpose
->governor() callback with a family of callbacks to carry out specific
governor operations: initialization and exit, start and stop and policy
limits updates. That also turns out to reduce the code size too, so
do it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Fix handling of special cases in dbs_update()

As reported in KBZ 69821:

"With CONFIG_HZ_PERIODIC=y cpu stays at the lowest frequcency 800MHz
even if usage goes to 100%, frequency does not scale up, the governor
in use is ondemand. Neither works conservative. Performance and
userspace governors work as expected.

With CONFIG_NO_HZ_IDLE or CONFIG_NO_HZ_FULL cpu scales up with ondemand
as expected."

Analysis carried out by Chen Yu leads to the conclusion that the
observed issue is due to idle_time in dbs_update() representing a
negative number in which case the function will return 0 as the load
(unless load is greater than 0 for another CPU sharing the policy),
although that need not be the right choice.

Indeed, idle_time representing a negative number means that during
the last sampling interval the CPU was almost 100% busy on the rough
average, so 100 should be returned as the load in that case.

Modify the code accordingly and rearrange it to clarify the handling
of all of the special cases in it. While at it, also avoid returning
zero as the load if time_elapsed is 0 (it doesn't really make sense
to return 0 then).

Link: https://bugzilla.kernel.org/show_bug.cgi?id=69821
Tested-by: Chen Yu <yu.c.chen@intel.com>
Tested-by: Timo Valtoaho <timo.valtoaho@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Change confusing struct field and variable names

The name of the prev_cpu_wall field in struct cpu_dbs_info is
confusing, because it doesn't represent wall time, but the previous
update time as returned by get_cpu_idle_time() (that may be the
current value of jiffies_64 in some cases, for example).

Moreover, the names of some related variables in dbs_update() take
that confusion further.

Rename all of those things to make their names reflect the purpose
more accurately. While at it, drop unnecessary parens from one of
the updated expressions.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Chen Yu <yu.c.chen@intel.com>

cpufreq: governor: Fix prev_load initialization in cpufreq_governor_start()

The way cpufreq_governor_start() initializes j_cdbs->prev_load is
questionable.

First off, j_cdbs->prev_cpu_wall used as a denominator in the
computation may be zero. The case this happens is when
get_cpu_idle_time_us() returns -1 and get_cpu_idle_time_jiffy()
used to return that number is called exactly at the jiffies_64
wrap time. It is rather hard to trigger that error, but it is not
impossible and it will just crash the kernel then.

Second, j_cdbs->prev_load is computed as the average load during
the entire time since the system started and it may not reflect the
load in the previous sampling period (as it is expected to).
That doesn't play well with the way dbs_update() uses that value.
Namely, if the update time delta (wall_time) happens do be greater
than twice the sampling rate on the first invocation of it, the
initial value of j_cdbs->prev_load (which may be completely off) will
be returned to the caller as the current load (unless it is equal to
zero and unless another CPU sharing the same policy object has a
greater load value).

For this reason, notice that the prev_load field of struct cpu_dbs_info
is only used by dbs_update() and only in that one place, so if
cpufreq_governor_start() is modified to always initialize it to 0,
it will make dbs_update() always compute the actual load first time
it checks the update time delta against the doubled sampling rate
(after initialization) and there won't be any side effects of it.

Consequently, modify cpufreq_governor_start() as described.

Fixes: 18b46abd0009 (cpufreq: governor: Be friendly towards latency-sensitive bursty workloads)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

Revert "cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC"

Revert commit 0df35026c6a5 (cpufreq: governor: Fix negative idle_time
when configured with CONFIG_HZ_PERIODIC) that introduced a regression
by causing the ondemand cpufreq governor to misbehave for
CONFIG_TICK_CPU_ACCOUNTING unset (the frequency goes up to the max at
one point and stays there indefinitely).

The revert takes subsequent modifications of the code in question into
account.

Fixes: 0df35026c6a5 (cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=115261
Reported-and-tested-by: Timo Valtoaho <timo.valtoaho@gmail.com>
Cc: 4.5+ <stable@vger.kernel.org> # 4.5+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Move abstract gov_attr_set code to seperate file

Move abstract code related to struct gov_attr_set to a separate (new)
file so it can be shared with (future) goverernors that won't share
more code with "ondemand" and "conservative".

No intentional functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: New data type for management part of dbs_data

In addition to fields representing governor tunables, struct dbs_data
contains some fields needed for the management of objects of that
type. As it turns out, that part of struct dbs_data may be shared
with (future) governors that won't use the common code used by
"ondemand" and "conservative", so move it to a separate struct type
and modify the code using struct dbs_data to follow.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: sched: Helpers to add and remove update_util hooks

Replace the single helper for adding and removing cpufreq utilization
update hooks, cpufreq_set_update_util_data(), with a pair of helpers,
cpufreq_add_update_util_hook() and cpufreq_remove_update_util_hook(),
and modify the users of cpufreq_set_update_util_data() accordingly.

With the new helpers, the code using them doesn't need to worry
about the internals of struct update_util_data and in particular
it doesn't need to worry about populating the func field in it
properly upfront.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

cpufreq: governor: Always schedule work on the CPU running update

Modify dbs_irq_work() to always schedule the process-context work
on the current CPU which also ran the dbs_update_util_handler()
that the irq_work being handled came from.

This causes the entire frequency update handling (involving the
"ondemand" or "conservative" governors) to be carried out by the
CPU whose frequency is to be updated and reduces the overall amount
of inter-CPU noise related to cpufreq.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Move scheduler-related code to the sched directory

Create cpufreq.c under kernel/sched/ and move the cpufreq code
related to the scheduler to that file and to sched.h.

Redefine cpufreq_update_util() as a static inline function to avoid
function calls at its call sites in the scheduler code (as suggested
by Peter Zijlstra).

Also move the definition of struct update_util_data and declaration
of cpufreq_set_update_util_data() from include/linux/cpufreq.h to
include/linux/sched.h.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

cpufreq: Reduce cpufreq_update_util() overhead a bit

Use the observation that cpufreq_update_util() is only called
by the scheduler with rq->lock held, so the callers of
cpufreq_set_update_util_data() can use synchronize_sched()
instead of synchronize_rcu() to wait for cpufreq_update_util()
to complete. Moreover, if they are updated to do that,
rcu_read_(un)lock() calls in cpufreq_update_util() might be
replaced with rcu_read_(un)lock_sched(), respectively, but
those aren't really necessary, because the scheduler calls
that function from RCU-sched read-side critical sections
already.

In addition to that, if cpufreq_set_update_util_data() checks
the func field in the struct update_util_data before setting
the per-CPU pointer to it, the data->func check may be dropped
from cpufreq_update_util() as well.

Make the above changes to reduce the overhead from
cpufreq_update_util() in the scheduler paths invoking it
and to make the cleanup after removing its callbacks less
heavy-weight somewhat.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

cpufreq: governor: Drop unnecessary checks from show() and store()

The show() and store() routines in the cpufreq-governor core don't need
to check if the struct governor_attr they want to use really provides
the callbacks they need as expected (if that's not the case, it means a
bug in the code anyway), so change them to avoid doing that.

Also change the error value to -EBUSY, if the governor is getting
removed and we aren't allowed to store any more changes.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Fix race in dbs_update_util_handler()

There is a scenario that may lead to undesired results in
dbs_update_util_handler(). Namely, if two CPUs sharing a policy
enter the funtion at the same time, pass the sample delay check
and then one of them is stalled until dbs_work_handler() (queued
up by the other CPU) clears the work counter, it may update the
work counter and queue up another work item prematurely.

To prevent that from happening, use the observation that the CPU
queuing up a work item in dbs_update_util_handler() updates the
last sample time. This means that if another CPU was stalling after
passing the sample delay check and now successfully updated the work
counter as a result of the race described above, it will see the new
value of the last sample time which is different from what it used in
the sample delay check before. If that happens, the sample delay
check passed previously is not valid any more, so the CPU should not
continue.

Fixes: f17cbb53783c (cpufreq: governor: Avoid atomic operations in hot paths)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Make gov_set_update_util() static

The gov_set_update_util() routine is only used internally by the
common governor code and it doesn't need to be exported, so make
it static.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Narrow down the dbs_data_mutex coverage

Since cpufreq_governor_dbs() is now always called with policy->rwsem
held, it cannot be executed twice in parallel for the same policy.
Thus it is not necessary to hold dbs_data_mutex around the invocations
of cpufreq_governor_start/stop/limits() from it as those functions
never modify any data that can be shared between different policies.

However, cpufreq_governor_dbs() may be executed twice in parallal
for different policies using the same gov->gdbs_data object and
dbs_data_mutex is still necessary to protect that object against
concurrent updates.

For this reason, narrow down the dbs_data_mutex locking to
cpufreq_governor_init/exit() where it is needed and rename the
mutex to gov_dbs_data_mutex to reflect its purpose.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Make dbs_data_mutex static

That mutex is only used by cpufreq_governor_dbs() and it doesn't
need to be exported to modules, so make it static and drop the
export incantation.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Move per-CPU data to the common code

After previous changes there is only one piece of code in the
ondemand governor making references to per-CPU data structures,
but it can be easily modified to avoid doing that, so modify it
accordingly and move the definition of per-CPU data used by the
ondemand and conservative governors to the common code. Next,
change that code to access the per-CPU data structures directly
rather than via a governor callback.

This causes the ->get_cpu_cdbs governor callback to become
unnecessary, so drop it along with the macro and function
definitions related to it.

Finally, drop the definitions of struct od_cpu_dbs_info_s and
struct cs_cpu_dbs_info_s that aren't necessary any more.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Make governor private data per-policy

Some fields in struct od_cpu_dbs_info_s and struct cs_cpu_dbs_info_s
are only used for a limited set of CPUs. Namely, if a policy is
shared between multiple CPUs, those fields will only be used for one
of them (policy->cpu). This means that they really are per-policy
rather than per-CPU and holding room for them in per-CPU data
structures is generally wasteful. Also moving those fields into
per-policy data structures will allow some significant simplifications
to be made going forward.

For this reason, introduce struct cs_policy_dbs_info and
struct od_policy_dbs_info to hold those fields. Define each of the
new structures as an extension of struct policy_dbs_info (such that
struct policy_dbs_info is embedded in each of them) and introduce
new ->alloc and ->free governor callbacks to allocate and free
those structures, respectively, such that ->alloc() will return
a pointer to the struct policy_dbs_info embedded in the allocated
data structure and ->free() will take that pointer as its argument.

With that, modify the code accessing the data fields in question
in per-CPU data objects to look for them in the new structures
via the struct policy_dbs_info pointer available to it and drop
them from struct od_cpu_dbs_info_s and struct cs_cpu_dbs_info_s.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Fix CPU load information updates via ->store

The ->store() callbacks of some tunable sysfs attributes of the
ondemand and conservative governors trigger immediate updates of
the CPU load information for all CPUs "governed" by the given
dbs_data by walking the cpu_dbs_info structures for all online
CPUs in the system and updating them.

This is questionable for two reasons. First, it may lead to a lot of
extra overhead on a system with many CPUs if the given dbs_data is
only associated with a few of them. Second, if governor tunables are
per-policy, the CPUs associated with the other sets of governor
tunables should not be updated.

To address this issue, use the observation that in all of the places
in question the update operation may be carried out in the same way
(because all of the tunables involved are now located in struct
dbs_data and readily available to the common code) and make the
code in those places invoke the same (new) helper function that
will carry out the update correctly.

That new function always checks the ignore_nice_load tunable value
and updates the CPUs' prev_cpu_nice data fields if that's set, which
wasn't done by the original code in store_io_is_busy(), but it
should have been done in there too.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Add a ->start callback for governors

To avoid having to check the governor type explicitly in the common
code in order to initialize data structures specific to the governor
type properly, add a ->start callback to struct dbs_governor and
use it to initialize those data structures for the ondemand and
conservative governors.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Move io_is_busy to struct dbs_data

The io_is_busy governor tunable is only used by the ondemand governor
and is located in the ondemand-specific data structure, but it is
looked at by the common governor code that has to do ugly things to
get to that value, so move it to struct dbs_data and modify ondemand
accordingly.

Since the conservative governor never touches that field, it will
be always 0 for that governor and it won't have any effect on the
results of computations in that case.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Close dbs_data update race condition

It is possible for a dbs_data object to be updated after its
usage counter has become 0. That may happen if governor_store()
runs (via a govenor tunable sysfs attribute write) in parallel
with cpufreq_governor_exit() called for the last cpufreq policy
associated with the dbs_data in question. In that case, if
governor_store() acquires dbs_data->mutex right after
cpufreq_governor_exit() has released it, the ->store() callback
invoked by it may operate on dbs_data with no users. Although
sysfs will cause the kobject_put() in cpufreq_governor_exit() to
block until governor_store() has returned, that situation may
lead to some unexpected results, depending on the implementation
of the ->store callback, and therefore it should be avoided.

To that end, modify governor_store() to check the dbs_data's
usage count before invoking the ->store() callback and return
an error if it is 0 at that point.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Use microseconds in sample delay computations

Do not convert microseconds to jiffies and the other way around
in governor computations related to the sampling rate and sample
delay and drop delay_for_sampling_rate() which isn't of any use
then.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Move rate_mult to struct policy_dbs

The rate_mult field in struct od_cpu_dbs_info_s is used by the code
shared with the conservative governor and to access it that code
has to do an ugly governor type check. However, first of all it
is ever only used for policy->cpu, so it is per-policy rather than
per-CPU and second, it is initialized to 1 by cpufreq_governor_start(),
so if the conservative governor never modifies it, it will have no
effect on the results of any computations.

For these reasons, move rate_mult to struct policy_dbs_info (as a
common field).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Reset sample delay in store_sampling_rate()

If store_sampling_rate() updates the sample delay when the ondemand
governor is in the middle of its high/low dance (OD_SUB_SAMPLE sample
type is set), the governor will still do the bottom half of the
previous sample which may take too much time.

To prevent that from happening, change store_sampling_rate() to always
reset the sample delay to 0 which also is consistent with the new
behavior of cpufreq_governor_limits().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Get rid of the ->gov_check_cpu callback

The way the ->gov_check_cpu governor callback is used by the ondemand
and conservative governors is not really straightforward. Namely, the
governor calls dbs_check_cpu() that updates the load information for
the policy and the invokes ->gov_check_cpu() for the governor.

To get rid of that entanglement, notice that cpufreq_governor_limits()
doesn't need to call dbs_check_cpu() directly. Instead, it can simply
reset the sample delay to 0 which will cause a sample to be taken
immediately. The result of that is practically equivalent to calling
dbs_check_cpu() except that it will trigger a full update of governor
internal state and not just the ->gov_check_cpu() part.

Following that observation, make cpufreq_governor_limits() reset
the sample delay and turn dbs_check_cpu() into a function that will
simply evaluate the load and return the result called dbs_update().

That function can now be called by governors from the routines that
previously were pointed to by ->gov_check_cpu and those routines
can be called directly by each governor instead of dbs_check_cpu().
This way ->gov_check_cpu becomes unnecessary, so drop it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Clean up load-related computations

Clean up some load-related computations in dbs_check_cpu() and
cpufreq_governor_start() to get rid of unnecessary operations and
type casts and make the code easier to read.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Fix nice contribution computation in dbs_check_cpu()

The contribution of the CPU nice time to the idle time in dbs_check_cpu()
is computed in a bogus way, as the code may subtract current and previous
nice values for different CPUs.

That doesn't matter for cases when cpufreq policies are not shared,
but may lead to problems otherwise.

Fix the computation and simplify it to avoid taking unnecessary steps.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Avoid atomic operations in hot paths

Rework the handling of work items by dbs_update_util_handler() and
dbs_work_handler() so the former (which is executed in scheduler
paths) only uses atomic operations when absolutely necessary. That
is, when the policy is shared and dbs_update_util_handler() has
already decided that this is the time to queue up a work item.

In particular, this avoids the atomic ops entirely on platforms where
policy objects are never shared.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Simplify gov_cancel_work() slightly

The atomic work counter incrementation in gov_cancel_work() is not
necessary any more, because work items won't be queued up after
gov_clear_update_util() anyway, so drop it along with the comment
about how it may be missed by the gov_clear_update_util().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Avoid irq_work_queue_on() crash on non-SMP ARM

As it turns out, irq_work_queue_on() will crash if invoked on
non-SMP ARM platforms, but in fact it is not necessary to use that
function in the cpufreq governor code (as it doesn't matter to that
code which CPU will handle the irq_work), so change it to always use
irq_work_queue().

Fixes: 8fb47ff100af (cpufreq: governor: Replace timers with utilization update callbacks)
Reported-and-tested-by: Guenter Roeck <linux@roeck-us.net>
Reported-and-tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: conservative: Update sample_delay_ns immediately

The ondemand governor already updates sample_delay_ns immediately on
updates to the sampling rate, but conservative doesn't do that.

It was left out earlier as the code was really too complex to get
that done easily. Things are sorted out very well now, however, and
the conservative governor can be modified to follow ondemand in that
respect.

Moreover, since the code needed to implement that in the
conservative governor would be identical to the corresponding
ondemand governor's code, make that code common and change both
governors to use it.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: No need to manage state machine now

The cpufreq core now guarantees that policy->rwsem won't be dropped
while running the ->governor callback for the CPUFREQ_GOV_POLICY_EXIT
event and will be held acquired until the complete sequence of governor
state changes has finished.

This allows governor state machine checks to be dropped from multiple
functions in cpufreq_governor.c.

This also means that policy_dbs->policy can be initialized upfront, so
the entire initialization of struct policy_dbs can be carried out in
one place.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Create and traverse list of policy_dbs to avoid deadlock

The dbs_data_mutex lock is currently used in two places. First,
cpufreq_governor_dbs() uses it to guarantee mutual exclusion between
invocations of governor operations from the core. Second, it is used by
ondemand governor's update_sampling_rate() to ensure the stability of
data structures walked by it.

The second usage is quite problematic, because update_sampling_rate() is
called from a governor sysfs attribute's ->store callback and that leads
to a deadlock scenario involving cpufreq_governor_exit() which runs
under dbs_data_mutex. Thus it is better to rework the code so
update_sampling_rate() doesn't need to acquire dbs_data_mutex.

To that end, rework update_sampling_rate() to walk a list of policy_dbs
objects supported by the dbs_data one it has been called for (instead of
walking cpu_dbs_info object for all CPUs). The list manipulation is
protected with dbs_data->mutex which also is held around the execution
of update_sampling_rate(), it is not necessary to hold dbs_data_mutex in
that function any more.

Reported-by: Juri Lelli <juri.lelli@arm.com>
Reported-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: New sysfs show/store callbacks for governor tunables

The ondemand and conservative governors use the global-attr or freq-attr
structures to represent sysfs attributes corresponding to their tunables
(which of them is actually used depends on whether or not different
policy objects can use the same governor with different tunables at the
same time and, consequently, on where those attributes are located in
sysfs).

Unfortunately, in the freq-attr case, the standard cpufreq show/store
sysfs attribute callbacks are applied to the governor tunable attributes
and they always acquire the policy->rwsem lock before carrying out the
operation. That may lead to an ABBA deadlock if governor tunable
attributes are removed under policy->rwsem while one of them is being
accessed concurrently (if sysfs attributes removal wins the race, it
will wait for the access to complete with policy->rwsem held while the
attribute callback will block on policy->rwsem indefinitely).

We attempted to address this issue by dropping policy->rwsem around
governor tunable attributes removal (that is, around invocations of the
->governor callback with the event arg equal to CPUFREQ_GOV_POLICY_EXIT)
in cpufreq_set_policy(), but that opened up race conditions that had not
been possible with policy->rwsem held all the time. Therefore
policy->rwsem cannot be dropped in cpufreq_set_policy() at any point,
but the deadlock situation described above must be avoided too.

To that end, use the observation that in principle governor tunables may
be represented by the same data type regardless of whether the governor
is system-wide or per-policy and introduce a new structure, struct
governor_attr, for representing them and new corresponding macros for
creating show/store sysfs callbacks for them. Also make their parent
kobject use a new kobject type whose default show/store callbacks are
not related to the standard core cpufreq ones in any way (and they don't
acquire policy->rwsem in particular).

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Subject & changelog + rebase ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Move common tunables to 'struct dbs_data'

There are a few common tunables shared between the ondemand and
conservative governors. Move them to struct dbs_data to simplify
code.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Drop pointless goto from cpufreq_governor_init()

It is silly to jump around "return 0", so don't do that.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Rename skip_work to work_count

The skip_work field in struct policy_dbs_info technically is a
counter, so give it a new name to reflect that.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Symmetrize cpu_dbs_info initialization and cleanup

Make the initialization of struct cpu_dbs_info objects in
alloc_policy_dbs_info() and the code that cleans them up in
free_policy_dbs_info() more symmetrical. In particular,
set/clear the update_util.func field in those functions along
with the policy_dbs field.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Rearrange governor data structures

The struct policy_dbs_info objects representing per-policy governor
data are not accessible directly from the corresponding policy
objects. To access them, one has to get a pointer to the
struct cpu_dbs_info of policy->cpu and use the policy_dbs field of
that which isn't really straightforward.

To address that rearrange the governor data structures so the
governor_data pointer in struct cpufreq_policy will point to
struct policy_dbs_info (instead of struct dbs_data) and that will
contain a pointer to struct dbs_data.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Simplify cpufreq_governor_limits()

Use the observation that cpufreq_governor_limits() doesn't have to
get to the policy object it wants to manipulate by walking the
reference chain cdbs->policy_dbs->policy, as the final pointer is
actually equal to its argument, and make it access the policy
object directy via its argument.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Drop cpu argument from dbs_check_cpu()

Since policy->cpu is always passed as the second argument to
dbs_check_cpu(), it is not really necessary to pass it, because
the function can obtain that value via its first argument just fine.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Rename cpu_common_dbs_info to policy_dbs_info

The struct cpu_common_dbs_info structure represents the per-policy
part of the governor data (for the ondemand and conservative
governors), but its name doesn't reflect its purpose.

Rename it to struct policy_dbs_info and rename variables related to
it accordingly.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Drop the gov pointer from struct dbs_data

Since it is possible to obtain a pointer to struct dbs_governor
from a pointer to the struct governor embedded in it with the help
of container_of(), the additional gov pointer in struct dbs_data
isn't really necessary.

Drop that pointer and make the code using it reach the dbs_governor
object via policy->governor.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Rework cpufreq_governor_dbs()

Since it is possible to obtain a pointer to struct dbs_governor
from a pointer to the struct governor embedded in it via
container_of(), the second argument of cpufreq_governor_init()
is not necessary. Accordingly, cpufreq_governor_dbs() doesn't
need its second argument either and the ->governor callbacks
for both the ondemand and conservative governors may be set
to cpufreq_governor_dbs() directly. Make that happen.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Rename some data types and variables

The ondemand and conservative governors are represented by
struct common_dbs_data whose name doesn't reflect the purpose it
is used for, so rename it to struct dbs_governor and rename
variables of that type accordingly.

No functional changes.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Avoid passing dbs_data pointers around unnecessarily

Do not pass struct dbs_data pointers to the family of functions
implementing governor operations in cpufreq_governor.c as they can
take that pointer from policy->governor by themselves.

The cpufreq_governor_init() case is slightly more complicated, since
policy->governor may be NULL when it is invoked, but then it can reach
the pointer in question via its cdata argument just fine.

While at it, rework cpufreq_governor_dbs() to avoid a pointless
policy_governor check in the CPUFREQ_GOV_POLICY_INIT case.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Use common mutex for dbs_data protection

Every governor relying on the common code in cpufreq_governor.c
has to provide its own mutex in struct common_dbs_data. However,
there actually is no need to have a separate mutex per governor
for this purpose, they may be using the same global mutex just
fine. Accordingly, introduce a single common mutex for that and
drop the mutex field from struct common_dbs_data.

That at least will ensure that the mutex is always present and
initialized regardless of what the particular governors do.

Another benefit is that the common code does not need a pointer to
a governor-related structure to get to the mutex which sometimes
helps.

Finally, it makes the code generally easier to follow.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Saravana Kannan <skannan@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: Replace timers with utilization update callbacks

Instead of using a per-CPU deferrable timer for queuing up governor
work items, register a utilization update callback that will be
invoked from the scheduler on utilization changes.

The sampling rate is still the same as what was used for the
deferrable timers and the added irq_work overhead should be offset by
the eliminated timers overhead, so in theory the functional impact of
this patch should not be significant.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

cpufreq: Fix NULL reference crash while accessing policy->governor_data

There is a race discovered by Juri, where we are able to:
- create and read a sysfs file before policy->governor_data is being set
to a non NULL value.
OR
- set policy->governor_data to NULL, and reading a file before being
destroyed.

And so such a crash is reported:

Unable to handle kernel NULL pointer dereference at virtual address 0000000c
pgd = edfc8000
[0000000c] *pgd=bfc8c835
Internal error: Oops: 17 [#1] SMP ARM
Modules linked in:
CPU: 4 PID: 1730 Comm: cat Not tainted 4.5.0-rc1+ #463
Hardware name: ARM-Versatile Express
task: ee8e8480 ti: ee930000 task.ti: ee930000
PC is at show_ignore_nice_load_gov_pol+0x24/0x34
LR is at show+0x4c/0x60
pc : [<c058f1bc>] lr : [<c058ae88>] psr: a0070013
sp : ee931dd0 ip : ee931de0 fp : ee931ddc
r10: ee4bc290 r9 : 00001000 r8 : ef2cb000
r7 : ee4bc200 r6 : ef2cb000 r5 : c0af57b0 r4 : ee4bc2e0
r3 : 00000000 r2 : 00000000 r1 : c0928df4 r0 : ef2cb000
Flags: NzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
Control: 10c5387d Table: adfc806a DAC: 00000051
Process cat (pid: 1730, stack limit = 0xee930210)
Stack: (0xee931dd0 to 0xee932000)
1dc0: ee931dfc ee931de0 c058ae88 c058f1a4
1de0: edce3bc0 c07bfca4 edce3ac0 00001000 ee931e24 ee931e00 c01fcb90 c058ae48
1e00: 00000001 edce3bc0 00000000 00000001 ee931e50 ee8ff480 ee931e34 ee931e28
1e20: c01fb33c c01fcb0c ee931e8c ee931e38 c01a5210 c01fb314 ee931e9c ee931e48
1e40: 00000000 edce3bf0 befe4a00 ee931f78 00000000 00000000 000001e4 00000000
1e60: c00545a8 edce3ac0 00001000 00001000 befe4a00 ee931f78 00000000 00001000
1e80: ee931ed4 ee931e90 c01fbed8 c01a5038 ed085a58 00020000 00000000 00000000
1ea0: c0ad72e4 ee931f78 ee8ff488 ee8ff480 c077f3fc 00001000 befe4a00 ee931f78
1ec0: 00000000 00001000 ee931f44 ee931ed8 c017c328 c01fbdc4 00001000 00000000
1ee0: ee8ff480 00001000 ee931f44 ee931ef8 c017c65c c03deb10 ee931fac ee931f08
1f00: c0009270 c001f290 c0a8d968 ef2cb000 ef2cb000 ee8ff480 00000020 ee8ff480
1f20: ee8ff480 befe4a00 00001000 ee931f78 00000000 00000000 ee931f74 ee931f48
1f40: c017d1ec c017c2f8 c019c724 c019c684 ee8ff480 ee8ff480 00001000 befe4a00
1f60: 00000000 00000000 ee931fa4 ee931f78 c017d2a8 c017d160 00000000 00000000
1f80: 000a9f20 00001000 befe4a00 00000003 c000ffe4 ee930000 00000000 ee931fa8
1fa0: c000fe40 c017d264 000a9f20 00001000 00000003 befe4a00 00001000 00000000
Unable to handle kernel NULL pointer dereference at virtual address 0000000c
1fc0: 000a9f20 00001000 befe4a00 00000003 00000000 00000000 00000003 00000001
pgd = edfc4000
[0000000c] *pgd=bfcac835
1fe0: 00000000 befe49dc 000197f8 b6e35dfc 60070010 00000003 3065b49d 134ac2c9

[<c058f1bc>] (show_ignore_nice_load_gov_pol) from [<c058ae88>] (show+0x4c/0x60)
[<c058ae88>] (show) from [<c01fcb90>] (sysfs_kf_seq_show+0x90/0xfc)
[<c01fcb90>] (sysfs_kf_seq_show) from [<c01fb33c>] (kernfs_seq_show+0x34/0x38)
[<c01fb33c>] (kernfs_seq_show) from [<c01a5210>] (seq_read+0x1e4/0x4e4)
[<c01a5210>] (seq_read) from [<c01fbed8>] (kernfs_fop_read+0x120/0x1a0)
[<c01fbed8>] (kernfs_fop_read) from [<c017c328>] (__vfs_read+0x3c/0xe0)
[<c017c328>] (__vfs_read) from [<c017d1ec>] (vfs_read+0x98/0x104)
[<c017d1ec>] (vfs_read) from [<c017d2a8>] (SyS_read+0x50/0x90)
[<c017d2a8>] (SyS_read) from [<c000fe40>] (ret_fast_syscall+0x0/0x1c)
Code: e5903044 e1a00001 e3081df4 e34c1092 (e593300c)
---[ end trace 5994b9a5111f35ee ]---

Fix that by making sure, policy->governor_data is updated at the right
places only.

Cc: 4.2+ <stable@vger.kernel.org> # 4.2+
Reported-and-tested-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Fix negative idle_time when configured with CONFIG_HZ_PERIODIC

It is reported that, with CONFIG_HZ_PERIODIC=y cpu stays at the
lowest frequency even if the usage goes to 100%, neither ondemand
nor conservative governor works, however performance and
userspace work as expected. If set with CONFIG_NO_HZ_FULL=y,
everything goes well.

This problem is caused by improper calculation of the idle_time
when the load is extremely high(near 100%). Firstly, cpufreq_governor
uses get_cpu_idle_time to get the total idle time for specific cpu, then:

1.If the system is configured with CONFIG_NO_HZ_FULL, the idle time is
returned by ktime_get, which is always increasing, it's OK.
2.However, if the system is configured with CONFIG_HZ_PERIODIC,
get_cpu_idle_time might not guarantee to be always increasing,
because it will leverage get_cpu_idle_time_jiffy to calculate the
idle_time, consider the following scenario:

At T1:
idle_tick_1 = total_tick_1 - user_tick_1

sample period(80ms)...

At T2: ( T2 = T1 + 80ms):
idle_tick_2 = total_tick_2 - user_tick_2

Currently the algorithm is using (idle_tick_2 - idle_tick_1) to
get the delta idle_time during the past sample period, however
it CAN NOT guarantee that idle_tick_2 >= idle_tick_1, especially
when cpu load is high.
(Yes, total_tick_2 >= total_tick_1, and user_tick_2 >= user_tick_1,
but how about idle_tick_2 and idle_tick_1? No guarantee.)
So governor might get a negative value of idle_time during the past
sample period, which might mislead the system that the idle time is
very big(converted to unsigned int), and the busy time is nearly zero,
which causes the governor to always choose the lowest cpufreq,
then cause this problem.

In theory there are two solutions:

1.The logic should not rely on the idle tick during every sample period,
but be based on the busy tick directly, as this is how 'top' is
implemented.

2.Or the logic must make sure that the idle_time is strictly increasing
during each sample period, then there would be no negative idle_time
anymore. This solution requires minimum modification to current code
and this patch uses method 2.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=69821
Reported-by: Jan Fikar <j.fikar@gmail.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Use lockless timer function

It is possible to get rid of the timer_lock spinlock used by the
governor timer function for synchronization, but a couple of races
need to be avoided.

The first race is between multiple dbs_timer_handler() instances
that may be running in parallel with each other on different
CPUs. Namely, one of them has to queue up the work item, but it
cannot be queued up more than once. To achieve that,
atomic_inc_return() can be used on the skip_work field of
struct cpu_common_dbs_info.

The second race is between an already running dbs_timer_handler()
and gov_cancel_work(). In that case the dbs_timer_handler() might
not notice the skip_work incrementation in gov_cancel_work() and
it might queue up its work item after gov_cancel_work() had
returned (and that work item would corrupt skip_work going
forward). To prevent that from happening, gov_cancel_work()
can be made wait for the timer function to complete (on all CPUs)
right after skip_work has been incremented.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: governor: replace per-CPU delayed work with timers

cpufreq governors evaluate load at sampling rate and based on that they
update frequency for a group of CPUs belonging to the same cpufreq
policy.

This is required to be done in a single thread for all policy->cpus, but
because we don't want to wakeup idle CPUs to do just that, we use
deferrable work for this. If we would have used a single delayed
deferrable work for the entire policy, there were chances that the CPU
required to run the handler can be in idle and we might end up not
changing the frequency for the entire group with load variations.

And so we were forced to keep per-cpu works, and only the one that
expires first need to do the real work and others are rescheduled for
next sampling time.

We have been using the more complex solution until now, where we used a
delayed deferrable work for this, which is a combination of a timer and
a work.

This could be made lightweight by keeping per-cpu deferred timers with a
single work item, which is scheduled by the first timer that expires.

This patch does just that and here are important changes:
- The timer handler will run in irq context and so we need to use a
spin_lock instead of the timer_mutex. And so a separate timer_lock is
created. This also makes the use of the mutex and lock quite clear, as
we know what exactly they are protecting.
- A new field 'skip_work' is added to track when the timer handlers can
queue a work. More comments present in code.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: initialize/destroy timer_mutex with 'shared'

timer_mutex is required to be initialized only while memory for 'shared'
is allocated and in a similar way it is required to be destroyed only
when memory for 'shared' is freed.

There is no need to do the same every time we start/stop the governor.
Move code to initialize/destroy timer_mutex to the relevant places.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Pass policy as argument to ->gov_dbs_timer()

Pass 'policy' as argument to ->gov_dbs_timer() instead of cdbs and
dbs_data.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Quit work-handlers early if governor is stopped

gov_queue_work() acquires cpufreq_governor_lock to allow
cpufreq_governor_stop() to drain delayed work items possibly scheduled
on CPUs that share the policy with a CPU being taken offline.

However, the same goal may be achieved in a more straightforward way if
the policy pointer in the struct cpu_dbs_info matching the policy CPU is
reset upfront by cpufreq_governor_stop() under the timer_mutex belonging
to it and checked against NULL, under the same lock, at the beginning of
dbs_timer().

In that case every instance of dbs_timer() run for a struct cpu_dbs_info
sharing the policy pointer in question after cpufreq_governor_stop() has
started will notice that that pointer is NULL and bail out immediately
without queuing up any new work items. In turn, gov_cancel_work()
called by cpufreq_governor_stop() before destroying timer_mutex will
wait for all of the delayed work items currently running on the CPUs
sharing the policy to drop the mutex, so it may be destroyed safely.

Make cpufreq_governor_stop() and dbs_timer() work as described and
modify gov_queue_work() so it does not acquire cpufreq_governor_lock any
more.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: create cpu/cpufreq at boot time

Later patches will need to create policy specific directories in
/sys/devices/system/cpu/cpufreq/ directory and so the cpufreq directory
wouldn't be ever empty.

And so no fun creating/destroying it on need basis anymore. Create it
once on system boot.

Reviewed-by: Saravana Kannan <skannan@codeaurora.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: conservative: remove 'enable' field

Conservative governor has its own 'enable' field to check if
conservative governor is used for a CPU or not

This can be checked by policy->governor with 'cpufreq_gov_conservative'
and so this field can be dropped.

Because its not guaranteed that dbs_info->cdbs.shared will a valid
pointer for all CPUs (will be NULL for CPUs that don't use
ondemand/conservative governors), we can't use it anymore. Lets get
policy with cpufreq_cpu_get_raw() instead.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Don't WARN on invalid states

With previous commit, governors have started to return errors on invalid
state-transition requests. We already have a WARN for an invalid
state-transition request in cpufreq_governor_dbs(). This does trigger
today, as the sequence of events isn't guaranteed by cpufreq core.

Lets stop warning on that for now, and make sure we don't enter an
invalid state.

Reviewed-and-tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Avoid invalid states with additional checks

There can be races where the request has come to a wrong state. For
example INIT followed by STOP (instead of START) or START followed by
EXIT (instead of STOP).

Address these races by making sure the state-machine never gets into
any invalid state. Also return an error if an invalid state-transition
is requested.

Reviewed-and-tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: split out common part of {cs|od}_dbs_timer()

Some part of cs_dbs_timer() and od_dbs_timer() is exactly same and is
unnecessarily duplicated.

Create the real work-handler in cpufreq_governor.c and put the common
code in this routine (dbs_timer()).

Shouldn't make any functional change.

Reviewed-and-tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Keep single copy of information common to policy->cpus

Some information is common to all CPUs belonging to a policy, but are
kept on per-cpu basis. Lets keep that in another structure common to all
policy->cpus. That will make updates/reads to that less complex and less
error prone.

The memory for cpu_common_dbs_info is allocated/freed at INIT/EXIT, so
that it we don't reallocate it for STOP/START sequence. It will be also
be used (in next patch) while the governor is stopped and so must not be
freed that early.

Reviewed-and-tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: rename cur_policy as policy

Just call it 'policy', cur_policy is unnecessarily long and doesn't
have any special meaning.

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: name pointer to cpu_dbs_info as 'cdbs'

It is called as 'cdbs' at most of the places and 'cpu_dbs' at others.
Lets use 'cdbs' consistently for better readability.

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Rename 'cpu_dbs_common_info' to 'cpu_dbs_info'

Its not common info to all CPUs, but a structure representing common
type of cpu info to both governor types. Lets drop 'common_' from its
name.

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Drop unused field 'cpu'

Its not used at all, drop it.

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Name delayed-work as dwork

Delayed work was named as 'work' and to access work within it we do
work.work. Not much readable. Rename delayed_work as 'dwork'.

Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Serialize governor callbacks

There are several races reported in cpufreq core around governors (only
ondemand and conservative) by different people.

There are at least two race scenarios present in governor code:
(a) Concurrent access/updates of governor internal structures.

It is possible that fields such as 'dbs_data->usage_count', etc. are
accessed simultaneously for different policies using same governor
structure (i.e. CPUFREQ_HAVE_GOVERNOR_PER_POLICY flag unset). And
because of this we can dereference bad pointers.

For example consider a system with two CPUs with separate 'struct
cpufreq_policy' instances. CPU0 governor: ondemand and CPU1: powersave.
CPU0 switching to powersave and CPU1 to ondemand:
CPU0 CPU1

store* store*

cpufreq_governor_exit() cpufreq_governor_init()
dbs_data = cdata->gdbs_data;

if (!--dbs_data->usage_count)
kfree(dbs_data);

dbs_data->usage_count++;
*Bad pointer dereference*

There are other races possible between EXIT and START/STOP/LIMIT as
well. Its really complicated.

(b) Switching governor state in bad sequence:

For example trying to switch a governor to START state, when the
governor is in EXIT state. There are some checks present in
__cpufreq_governor() but they aren't sufficient as they compare events
against 'policy->governor_enabled', where as we need to take governor's
state into account, which can be used by multiple policies.

These two issues need to be solved separately and the responsibility
should be properly divided between cpufreq and governor core.

The first problem is more about the governor core, as it needs to
protect its structures properly. And the second problem should be fixed
in cpufreq core instead of governor, as its all about sequence of
events.

This patch is trying to solve only the first problem.

There are two types of data we need to protect,
- 'struct common_dbs_data': No matter what, there is going to be a
single copy of this per governor.
- 'struct dbs_data': With CPUFREQ_HAVE_GOVERNOR_PER_POLICY flag set, we
will have per-policy copy of this data, otherwise a single copy.

Because of such complexities, the mutex present in 'struct dbs_data' is
insufficient to solve our problem. For example we need to protect
fetching of 'dbs_data' from different structures at the beginning of
cpufreq_governor_dbs(), to make sure it isn't currently being updated.

This can be fixed if we can guarantee serialization of event parsing
code for an individual governor. This is best solved with a mutex per
governor, and the placeholder for that is 'struct common_dbs_data'.

And so this patch moves the mutex from 'struct dbs_data' to 'struct
common_dbs_data' and takes it at the beginning and drops it at the end
of cpufreq_governor_dbs().

Tested with and without following configuration options:

CONFIG_LOCKDEP_SUPPORT=y
CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_PI_LIST=y
CONFIG_DEBUG_SPINLOCK=y
CONFIG_DEBUG_MUTEXES=y
CONFIG_DEBUG_LOCK_ALLOC=y
CONFIG_PROVE_LOCKING=y
CONFIG_LOCKDEP=y
CONFIG_DEBUG_ATOMIC_SLEEP=y

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: split cpufreq_governor_dbs()

cpufreq_governor_dbs() is hardly readable, it is just too big and
complicated. Lets make it more readable by splitting out event specific
routines.

Order of statements is changed at few places, but that shouldn't bring
any functional change.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: register notifier from cs_init()

Notifiers are required only for conservative governor and the common
governor code is unnecessarily polluted with that. Handle that from
cs_init/exit() instead of cpufreq_governor_dbs().

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: remove copy_prev_load from 'struct cpu_dbs_common_info'

'copy_prev_load' was recently added by commit: 18b46ab (cpufreq: governor: Be
friendly towards latency-sensitive bursty workloads).

It actually is a bit redundant as we also have 'prev_load' which can store any
integer value and can be used instead of 'copy_prev_load' by setting it zero.

True load can also turn out to be zero during long idle intervals (and hence the
actual value of 'prev_load' and the overloaded value can clash). However this is
not a problem because, if the true load was really zero in the previous
interval, it makes sense to evaluate the load afresh for the current interval
rather than copying the previous load.

So, drop 'copy_prev_load' and use 'prev_load' instead.

Update comments as well to make it more clear.

There is another change here which was probably missed by Srivatsa during the
last version of updates he made. The unlikely in the 'if' statement was covering
only half of the condition and the whole line should actually come under it.

Also checkpatch is made more silent as it was reporting this (--strict option):

CHECK: Alignment should match open parenthesis
+ if (unlikely(wall_time > (2 * sampling_rate) &&
+ j_cdbs->prev_load)) {

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Be friendly towards latency-sensitive bursty workloads

Cpufreq governors like the ondemand governor calculate the load on the CPU
periodically by employing deferrable timers. A deferrable timer won't fire
if the CPU is completely idle (and there are no other timers to be run), in
order to avoid unnecessary wakeups and thus save CPU power.

However, the load calculation logic is agnostic to all this, and this can
lead to the problem described below.

Time (ms) CPU 1

100 Task-A running

110 Governor's timer fires, finds load as 100% in the last
10ms interval and increases the CPU frequency.

110.5 Task-A running

120 Governor's timer fires, finds load as 100% in the last
10ms interval and increases the CPU frequency.

125 Task-A went to sleep. With nothing else to do, CPU 1
went completely idle.

200 Task-A woke up and started running again.

200.5 Governor's deferred timer (which was originally programmed
to fire at time 130) fires now. It calculates load for the
time period 120 to 200.5, and finds the load is almost zero.
Hence it decreases the CPU frequency to the minimum.

210 Governor's timer fires, finds load as 100% in the last
10ms interval and increases the CPU frequency.

So, after the workload woke up and started running, the frequency was suddenly
dropped to absolute minimum, and after that, there was an unnecessary delay of
10ms (sampling period) to increase the CPU frequency back to a reasonable value.
And this pattern repeats for every wake-up-from-cpu-idle for that workload.
This can be quite undesirable for latency- or response-time sensitive bursty
workloads. So we need to fix the governor's logic to detect such wake-up-from-
cpu-idle scenarios and start the workload at a reasonably high CPU frequency.

One extreme solution would be to fake a load of 100% in such scenarios. But
that might lead to undesirable side-effects such as frequency spikes (which
might also need voltage changes) especially if the previous frequency happened
to be very low.

We just want to avoid the stupidity of dropping down the frequency to a minimum
and then enduring a needless (and long) delay before ramping it up back again.
So, let us simply carry forward the previous load - that is, let us just pretend
that the 'load' for the current time-window is the same as the load for the
previous window. That way, the frequency and voltage will continue to be set
to whatever values they were set at previously. This means that bursty workloads
will get a chance to influence the CPU frequency at which they wake up from
cpu-idle, based on their past execution history. Thus, they might be able to
avoid suffering from slow wakeups and long response-times.

However, we should take care not to over-do this. For example, such a "copy
previous load" logic will benefit cases like this: (where # represents busy
and . represents idle)

##########.........#########.........###########...........##########........

but it will be detrimental in cases like the one shown below, because it will
retain the high frequency (copied from the previous interval) even in a mostly
idle system:

##########.........#.................#.....................#...............

(i.e., the workload finished and the remaining tasks are such that their busy
periods are smaller than the sampling interval, which causes the timer to
always get deferred. So, this will make the copy-previous-load logic copy
the initial high load to subsequent idle periods over and over again, thus
keeping the frequency high unnecessarily).

So, we modify this copy-previous-load logic such that it is used only once
upon every wakeup-from-idle. Thus if we have 2 consecutive idle periods, the
previous load won't get blindly copied over; cpufreq will freshly evaluate the
load in the second idle interval, thus ensuring that the system comes back to
its normal state.

[ The right way to solve this whole problem is to teach the CPU frequency
governors to also track load on a per-task basis, not just a per-CPU basis,
and then use both the data sources intelligently to set the appropriate
frequency on the CPUs. But that involves redesigning the cpufreq subsystem,
so this patch should make the situation bearable until then. ]

Experimental results:
+-------------------+

I ran a modified version of ebizzy (called 'sleeping-ebizzy') that sleeps in
between its execution such that its total utilization can be a user-defined
value, say 10% or 20% (higher the utilization specified, lesser the amount of
sleeps injected). This ebizzy was run with a single-thread, tied to CPU 8.

Behavior observed with tracing (sample taken from 40% utilization runs):
------------------------------------------------------------------------

Without patch:
~~~~~~~~~~~~~~
kworker/8:2-12137 416.335742: cpu_frequency: state=2061000 cpu_id=8
kworker/8:2-12137 416.335744: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40753 416.345741: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
kworker/8:2-12137 416.345744: cpu_frequency: state=4123000 cpu_id=8
kworker/8:2-12137 416.345746: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40753 416.355738: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
<snip> --------------------------------------------------------------------- <snip>
<...>-40753 416.402202: sched_switch: prev_comm=ebizzy ==> next_comm=swapper/8
<idle>-0 416.502130: sched_switch: prev_comm=swapper/8 ==> next_comm=ebizzy
<...>-40753 416.505738: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
kworker/8:2-12137 416.505739: cpu_frequency: state=2061000 cpu_id=8
kworker/8:2-12137 416.505741: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40753 416.515739: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
kworker/8:2-12137 416.515742: cpu_frequency: state=4123000 cpu_id=8
kworker/8:2-12137 416.515744: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy

Observation: Ebizzy went idle at 416.402202, and started running again at
416.502130. But cpufreq noticed the long idle period, and dropped the frequency
at 416.505739, only to increase it back again at 416.515742, realizing that the
workload is in-fact CPU bound. Thus ebizzy needlessly ran at the lowest frequency
for almost 13 milliseconds (almost 1 full sample period), and this pattern
repeats on every sleep-wakeup. This could hurt latency-sensitive workloads quite
a lot.

With patch:
~~~~~~~~~~~

kworker/8:2-29802 464.832535: cpu_frequency: state=2061000 cpu_id=8
<snip> --------------------------------------------------------------------- <snip>
kworker/8:2-29802 464.962538: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40738 464.972533: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
kworker/8:2-29802 464.972536: cpu_frequency: state=4123000 cpu_id=8
kworker/8:2-29802 464.972538: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40738 464.982531: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
<snip> --------------------------------------------------------------------- <snip>
kworker/8:2-29802 465.022533: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40738 465.032531: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
kworker/8:2-29802 465.032532: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40738 465.035797: sched_switch: prev_comm=ebizzy ==> next_comm=swapper/8
<idle>-0 465.240178: sched_switch: prev_comm=swapper/8 ==> next_comm=ebizzy
<...>-40738 465.242533: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2
kworker/8:2-29802 465.242535: sched_switch: prev_comm=kworker/8:2 ==> next_comm=ebizzy
<...>-40738 465.252531: sched_switch: prev_comm=ebizzy ==> next_comm=kworker/8:2

Observation: Ebizzy went idle at 465.035797, and started running again at
465.240178. Since ebizzy was the only real workload running on this CPU,
cpufreq retained the frequency at 4.1Ghz throughout the run of ebizzy, no
matter how many times ebizzy slept and woke-up in-between. Thus, ebizzy
got the 10ms worth of 4.1 Ghz benefit during every sleep-wakeup (as compared
to the run without the patch) and this boost gave a modest improvement in total
throughput, as shown below.

Sleeping-ebizzy records-per-second:
-----------------------------------

Utilization Without patch With patch Difference (Absolute and % values)
10% 274767 277046 + 2279 (+0.829%)
20% 543429 553484 + 10055 (+1.850%)
40% 1090744 1107959 + 17215 (+1.578%)
60% 1634908 1662018 + 27110 (+1.658%)

A rudimentary and somewhat approximately latency-sensitive workload such as
sleeping-ebizzy itself showed a consistent, noticeable performance improvement
with this patch. Hence, workloads that are truly latency-sensitive will benefit
quite a bit from this change. Moreover, this is an overall win-win since this
patch does not hurt power-savings at all (because, this patch does not reduce
the idle time or idle residency; and the high frequency of the CPU when it goes
to cpu-idle does not affect/hurt the power-savings of deep idle states).

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: remove race while accessing cur_policy

While accessing cur_policy during executing events
CPUFREQ_GOV_START, CPUFREQ_GOV_STOP, CPUFREQ_GOV_LIMITS,
same mutex lock is not taken, dbs_data->mutex, which leads
to race and data corruption while running continious suspend
resume test. This is seen with ondemand governor with suspend
resume test using rtcwake.

Unable to handle kernel NULL pointer dereference at virtual address 00000028
pgd = ed610000
[00000028] *pgd=adf11831, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1] PREEMPT SMP ARM
Modules linked in: nvhost_vi
CPU: 1 PID: 3243 Comm: rtcwake Not tainted 3.10.24-gf5cf9e5 #1
task: ee708040 ti: ed61c000 task.ti: ed61c000
PC is at cpufreq_governor_dbs+0x400/0x634
LR is at cpufreq_governor_dbs+0x3f8/0x634
pc : [<c05652b8>] lr : [<c05652b0>] psr: 600f0013
sp : ed61dcb0 ip : 000493e0 fp : c1cc14f0
r10: 00000000 r9 : 00000000 r8 : 00000000
r7 : eb725280 r6 : c1cc1560 r5 : eb575200 r4 : ebad7740
r3 : ee708040 r2 : ed61dca8 r1 : 001ebd24 r0 : 00000000
Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
Control: 10c5387d Table: ad61006a DAC: 00000015
[<c05652b8>] (cpufreq_governor_dbs+0x400/0x634) from [<c055f700>] (__cpufreq_governor+0x98/0x1b4)
[<c055f700>] (__cpufreq_governor+0x98/0x1b4) from [<c0560770>] (__cpufreq_set_policy+0x250/0x320)
[<c0560770>] (__cpufreq_set_policy+0x250/0x320) from [<c0561dcc>] (cpufreq_update_policy+0xcc/0x168)
[<c0561dcc>] (cpufreq_update_policy+0xcc/0x168) from [<c0561ed0>] (cpu_freq_notify+0x68/0xdc)
[<c0561ed0>] (cpu_freq_notify+0x68/0xdc) from [<c008eff8>] (notifier_call_chain+0x4c/0x8c)
[<c008eff8>] (notifier_call_chain+0x4c/0x8c) from [<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68)
[<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68) from [<c008f40c>] (blocking_notifier_call_chain+0x20/0x28)
[<c008f40c>] (blocking_notifier_call_chain+0x20/0x28) from [<c00aac6c>] (pm_qos_update_bounded_target+0xd8/0x310)
[<c00aac6c>] (pm_qos_update_bounded_target+0xd8/0x310) from [<c00ab3b0>] (__pm_qos_update_request+0x64/0x70)
[<c00ab3b0>] (__pm_qos_update_request+0x64/0x70) from [<c004b4b8>] (tegra_pm_notify+0x114/0x134)
[<c004b4b8>] (tegra_pm_notify+0x114/0x134) from [<c008eff8>] (notifier_call_chain+0x4c/0x8c)
[<c008eff8>] (notifier_call_chain+0x4c/0x8c) from [<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68)
[<c008f3d4>] (__blocking_notifier_call_chain+0x50/0x68) from [<c008f40c>] (blocking_notifier_call_chain+0x20/0x28)
[<c008f40c>] (blocking_notifier_call_chain+0x20/0x28) from [<c00ac228>] (pm_notifier_call_chain+0x1c/0x34)
[<c00ac228>] (pm_notifier_call_chain+0x1c/0x34) from [<c00ad38c>] (enter_state+0xec/0x128)
[<c00ad38c>] (enter_state+0xec/0x128) from [<c00ad400>] (pm_suspend+0x38/0xa4)
[<c00ad400>] (pm_suspend+0x38/0xa4) from [<c00ac114>] (state_store+0x70/0xc0)
[<c00ac114>] (state_store+0x70/0xc0) from [<c027b1e8>] (kobj_attr_store+0x14/0x20)
[<c027b1e8>] (kobj_attr_store+0x14/0x20) from [<c019cd9c>] (sysfs_write_file+0x104/0x184)
[<c019cd9c>] (sysfs_write_file+0x104/0x184) from [<c0143038>] (vfs_write+0xd0/0x19c)
[<c0143038>] (vfs_write+0xd0/0x19c) from [<c0143414>] (SyS_write+0x4c/0x78)
[<c0143414>] (SyS_write+0x4c/0x78) from [<c000f080>] (ret_fast_syscall+0x0/0x30)
Code: e1a00006 eb084346 e59b0020 e5951024 (e5903028)
---[ end trace 0488523c8f6b0f9d ]---

Signed-off-by: Bibek Basu <bbasu@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: 3.11+ <stable@vger.kernel.org> # 3.11+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Fix timer/workqueue corruption by protecting reading governor_enabled

When a CPU is hot removed we'll cancel all the delayed work items via
gov_cancel_work(). Sometimes the delayed work function determines that
it should adjust the delay for all other CPUs that the policy is
managing. If this scenario occurs, the canceling CPU will cancel its own
work but queue up the other CPUs works to run.

Commit 3617f2 (cpufreq: Fix timer/workqueue corruption due to double
queueing) has tried to fix this, but reading governor_enabled is not
protected by cpufreq_governor_lock. Even though od_dbs_timer() checks
governor_enabled before gov_queue_work(), this scenario may occur. For
example:

CPU0 CPU1
---- ----
cpu_down()
... <work runs>
__cpufreq_remove_dev() od_dbs_timer()
__cpufreq_governor() policy->governor_enabled
policy->governor_enabled = false;
cpufreq_governor_dbs()
case CPUFREQ_GOV_STOP:
gov_cancel_work(dbs_data, policy);
cpu0 work is canceled
timer is canceled
cpu1 work is canceled
<waits for cpu1>
gov_queue_work(*, *, true);
cpu0 work queued
cpu1 work queued
cpu2 work queued
...
cpu1 work is canceled
cpu2 work is canceled
...

At the end of the GOV_STOP case cpu0 still has a work queued to
run although the code is expecting all of the works to be
canceled. __cpufreq_remove_dev() will then proceed to
re-initialize all the other CPUs works except for the CPU that is
going down. The CPUFREQ_GOV_START case in cpufreq_governor_dbs()
will trample over the queued work and debugobjects will spit out
a warning:

WARNING: at lib/debugobjects.c:260 debug_print_object+0x94/0xbc()
ODEBUG: init active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x14
Modules linked in:
CPU: 1 PID: 1205 Comm: sh Tainted: G W 3.10.0 #200
[<c01144f0>] (unwind_backtrace+0x0/0xf8) from [<c0111d98>] (show_stack+0x10/0x14)
[<c0111d98>] (show_stack+0x10/0x14) from [<c01272cc>] (warn_slowpath_common+0x4c/0x68)
[<c01272cc>] (warn_slowpath_common+0x4c/0x68) from [<c012737c>] (warn_slowpath_fmt+0x30/0x40)
[<c012737c>] (warn_slowpath_fmt+0x30/0x40) from [<c034c640>] (debug_print_object+0x94/0xbc)
[<c034c640>] (debug_print_object+0x94/0xbc) from [<c034c7f8>] (__debug_object_init+0xc8/0x3c0)
[<c034c7f8>] (__debug_object_init+0xc8/0x3c0) from [<c01360e0>] (init_timer_key+0x20/0x104)
[<c01360e0>] (init_timer_key+0x20/0x104) from [<c04872ac>] (cpufreq_governor_dbs+0x1dc/0x68c)
[<c04872ac>] (cpufreq_governor_dbs+0x1dc/0x68c) from [<c04833a8>] (__cpufreq_governor+0x80/0x1b0)
[<c04833a8>] (__cpufreq_governor+0x80/0x1b0) from [<c0483704>] (__cpufreq_remove_dev.isra.12+0x22c/0x380)
[<c0483704>] (__cpufreq_remove_dev.isra.12+0x22c/0x380) from [<c0692f38>] (cpufreq_cpu_callback+0x48/0x5c)
[<c0692f38>] (cpufreq_cpu_callback+0x48/0x5c) from [<c014fb40>] (notifier_call_chain+0x44/0x84)
[<c014fb40>] (notifier_call_chain+0x44/0x84) from [<c012ae44>] (__cpu_notify+0x2c/0x48)
[<c012ae44>] (__cpu_notify+0x2c/0x48) from [<c068dd40>] (_cpu_down+0x80/0x258)
[<c068dd40>] (_cpu_down+0x80/0x258) from [<c068df40>] (cpu_down+0x28/0x3c)
[<c068df40>] (cpu_down+0x28/0x3c) from [<c068e4c0>] (store_online+0x30/0x74)
[<c068e4c0>] (store_online+0x30/0x74) from [<c03a7308>] (dev_attr_store+0x18/0x24)
[<c03a7308>] (dev_attr_store+0x18/0x24) from [<c0256fe0>] (sysfs_write_file+0x100/0x180)
[<c0256fe0>] (sysfs_write_file+0x100/0x180) from [<c01fec9c>] (vfs_write+0xbc/0x184)
[<c01fec9c>] (vfs_write+0xbc/0x184) from [<c01ff034>] (SyS_write+0x40/0x68)
[<c01ff034>] (SyS_write+0x40/0x68) from [<c010e200>] (ret_fast_syscall+0x0/0x48)

In gov_queue_work(), lock cpufreq_governor_lock before gov_queue_work,
and unlock it after __gov_queue_work(). In this way, governor_enabled
is guaranteed not changed in gov_queue_work().

Signed-off-by: Jane Li <jiel@marvell.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Remove fossil comment in the cpufreq_governor_dbs()

The related code has been changed and the comment is out of date.
So remove it.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Don't use smp_processor_id() in preemptible context

Workqueues are preemptible even if works are queued on them with
queue_work_on(). Let's use raw_smp_processor_id() here to silence
the warning.

BUG: using smp_processor_id() in preemptible [00000000] code: kworker/3:2/674
caller is gov_queue_work+0x28/0xb0
CPU: 0 PID: 674 Comm: kworker/3:2 Tainted: G W 3.10.0 #30
Workqueue: events od_dbs_timer
[<c010c178>] (unwind_backtrace+0x0/0x11c) from [<c0109dec>] (show_stack+0x10/0x14)
[<c0109dec>] (show_stack+0x10/0x14) from [<c03885a4>] (debug_smp_processor_id+0xbc/0xf0)
[<c03885a4>] (debug_smp_processor_id+0xbc/0xf0) from [<c0635864>] (gov_queue_work+0x28/0xb0)
[<c0635864>] (gov_queue_work+0x28/0xb0) from [<c0635618>] (od_dbs_timer+0x108/0x134)
[<c0635618>] (od_dbs_timer+0x108/0x134) from [<c01aa8f8>] (process_one_work+0x25c/0x444)
[<c01aa8f8>] (process_one_work+0x25c/0x444) from [<c01aaf88>] (worker_thread+0x200/0x344)
[<c01aaf88>] (worker_thread+0x200/0x344) from [<c01b03bc>] (kthread+0xa0/0xb0)
[<c01b03bc>] (kthread+0xa0/0xb0) from [<c01061b8>] (ret_from_fork+0x14/0x3c)

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Fix typos in comments

- 'Governer' should be 'Governor'.
- 'S' is used for Siemens (electrical conductance) in SI units,
so use small 's' for seconds.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Fix timer/workqueue corruption due to double queueing

When a CPU is hot removed we'll cancel all the delayed work items
via gov_cancel_work(). Normally this will just cancels a delayed
timer on each CPU that the policy is managing and the work won't
run, but if the work is already running the workqueue code will
wait for the work to finish before continuing to prevent the
work items from re-queuing themselves like they normally do. This
scheme will work most of the time, except for the case where the
work function determines that it should adjust the delay for all
other CPUs that the policy is managing. If this scenario occurs,
the canceling CPU will cancel its own work but queue up the other
CPUs works to run. For example:

CPU0 CPU1
---- ----
cpu_down()
...
__cpufreq_remove_dev()
cpufreq_governor_dbs()
case CPUFREQ_GOV_STOP:
gov_cancel_work(dbs_data, policy);
cpu0 work is canceled
timer is canceled
cpu1 work is canceled <work runs>
<waits for cpu1> od_dbs_timer()
gov_queue_work(*, *, true);
cpu0 work queued
cpu1 work queued
cpu2 work queued
...
cpu1 work is canceled
cpu2 work is canceled
...

At the end of the GOV_STOP case cpu0 still has a work queued to
run although the code is expecting all of the works to be
canceled. __cpufreq_remove_dev() will then proceed to
re-initialize all the other CPUs works except for the CPU that is
going down. The CPUFREQ_GOV_START case in cpufreq_governor_dbs()
will trample over the queued work and debugobjects will spit out
a warning:

WARNING: at lib/debugobjects.c:260 debug_print_object+0x94/0xbc()
ODEBUG: init active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x10
Modules linked in:
CPU: 0 PID: 1491 Comm: sh Tainted: G W 3.10.0 #19
[<c010c178>] (unwind_backtrace+0x0/0x11c) from [<c0109dec>] (show_stack+0x10/0x14)
[<c0109dec>] (show_stack+0x10/0x14) from [<c01904cc>] (warn_slowpath_common+0x4c/0x6c)
[<c01904cc>] (warn_slowpath_common+0x4c/0x6c) from [<c019056c>] (warn_slowpath_fmt+0x2c/0x3c)
[<c019056c>] (warn_slowpath_fmt+0x2c/0x3c) from [<c0388a7c>] (debug_print_object+0x94/0xbc)
[<c0388a7c>] (debug_print_object+0x94/0xbc) from [<c0388e34>] (__debug_object_init+0x2d0/0x340)
[<c0388e34>] (__debug_object_init+0x2d0/0x340) from [<c019e3b0>] (init_timer_key+0x14/0xb0)
[<c019e3b0>] (init_timer_key+0x14/0xb0) from [<c0635f78>] (cpufreq_governor_dbs+0x3e8/0x5f8)
[<c0635f78>] (cpufreq_governor_dbs+0x3e8/0x5f8) from [<c06325a0>] (__cpufreq_governor+0xdc/0x1a4)
[<c06325a0>] (__cpufreq_governor+0xdc/0x1a4) from [<c0633704>] (__cpufreq_remove_dev.isra.10+0x3b4/0x434)
[<c0633704>] (__cpufreq_remove_dev.isra.10+0x3b4/0x434) from [<c08989f4>] (cpufreq_cpu_callback+0x60/0x80)
[<c08989f4>] (cpufreq_cpu_callback+0x60/0x80) from [<c08a43c0>] (notifier_call_chain+0x38/0x68)
[<c08a43c0>] (notifier_call_chain+0x38/0x68) from [<c01938e0>] (__cpu_notify+0x28/0x40)
[<c01938e0>] (__cpu_notify+0x28/0x40) from [<c0892ad4>] (_cpu_down+0x7c/0x2c0)
[<c0892ad4>] (_cpu_down+0x7c/0x2c0) from [<c0892d3c>] (cpu_down+0x24/0x40)
[<c0892d3c>] (cpu_down+0x24/0x40) from [<c0893ea8>] (store_online+0x2c/0x74)
[<c0893ea8>] (store_online+0x2c/0x74) from [<c04519d8>] (dev_attr_store+0x18/0x24)
[<c04519d8>] (dev_attr_store+0x18/0x24) from [<c02a69d4>] (sysfs_write_file+0x100/0x148)
[<c02a69d4>] (sysfs_write_file+0x100/0x148) from [<c0255c18>] (vfs_write+0xcc/0x174)
[<c0255c18>] (vfs_write+0xcc/0x174) from [<c0255f70>] (SyS_write+0x38/0x64)
[<c0255f70>] (SyS_write+0x38/0x64) from [<c0106120>] (ret_fast_syscall+0x0/0x30)

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Clean up header files included in the core

This patch addresses the following issues in the header files in the
cpufreq core:
- Include headers in ascending order, so that we don't add same
many times by mistake.
- <asm/> must be included after <linux/>, so that they override
whatever they need to.
- Remove unnecessary includes.
- Don't include files already included by cpufreq.h or
cpufreq_governor.h.

[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: rename ignore_nice as ignore_nice_load

This sysfs file was called ignore_nice_load earlier and commit
4d5dcc4 (cpufreq: governor: Implement per policy instances of
governors) changed its name to ignore_nice by mistake.

Lets get it renamed back to its original name.

Reported-by: Martin von Gagern <Martin.vGagern@gmx.net>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: 3.10+ <stable@vger.kernel.org> # 3.10+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: ondemand: Change the calculation of target frequency

The ondemand governor calculates load in terms of frequency and
increases it only if load_freq is greater than up_threshold
multiplied by the current or average frequency. This appears to
produce oscillations of frequency between min and max because,
for example, a relatively small load can easily saturate minimum
frequency and lead the CPU to the max. Then, it will decrease
back to the min due to small load_freq.

Change the calculation method of load and target frequency on the
basis of the following two observations:

- Load computation should not depend on the current or average
measured frequency. For example, absolute load of 80% at 100MHz
is not necessarily equivalent to 8% at 1000MHz in the next
sampling interval.

- It should be possible to increase the target frequency to any
value present in the frequency table proportional to the absolute
load, rather than to the max only, so that:

Target frequency = C * load

where we take C = policy->cpuinfo.max_freq / 100.

Tested on Intel i7-3770 CPU @ 3.40GHz and on Quad core 1500MHz Krait.
Phoronix benchmark of Linux Kernel Compilation 3.1 test shows an
increase ~1.5% in performance. cpufreq_stats (time_in_state) shows
that middle frequencies are used more, with this patch. Highest
and lowest frequencies were used less by ~9%.

[rjw: We have run multiple other tests on kernels with this
change applied and in the vast majority of cases it turns out
that the resulting performance improvement also leads to reduced
consumption of energy. The change is additionally justified by
the overall simplification of the code in question.]

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Revert commit 2f7021a8 to fix CPU hotplug regression

commit 2f7021a8 "cpufreq: protect 'policy->cpus' from offlining
during __gov_queue_work()" caused a regression in CPU hotplug,
because it lead to a deadlock between cpufreq governor worker thread
and the CPU hotplug writer task.

Lockdep splat corresponding to this deadlock is shown below:

[ 60.277396] ======================================================
[ 60.277400] [ INFO: possible circular locking dependency detected ]
[ 60.277407] 3.10.0-rc7-dbg-01385-g241fd04-dirty #1744 Not tainted
[ 60.277411] -------------------------------------------------------
[ 60.277417] bash/2225 is trying to acquire lock:
[ 60.277422] ((&(&j_cdbs->work)->work)){+.+...}, at: [<ffffffff810621b5>] flush_work+0x5/0x280
[ 60.277444] but task is already holding lock:
[ 60.277449] (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff81042d8b>] cpu_hotplug_begin+0x2b/0x60
[ 60.277465] which lock already depends on the new lock.

[ 60.277472] the existing dependency chain (in reverse order) is:
[ 60.277477] -> #2 (cpu_hotplug.lock){+.+.+.}:
[ 60.277490] [<ffffffff810ac6d4>] lock_acquire+0xa4/0x200
[ 60.277503] [<ffffffff815b6157>] mutex_lock_nested+0x67/0x410
[ 60.277514] [<ffffffff81042cbc>] get_online_cpus+0x3c/0x60
[ 60.277522] [<ffffffff814b842a>] gov_queue_work+0x2a/0xb0
[ 60.277532] [<ffffffff814b7891>] cs_dbs_timer+0xc1/0xe0
[ 60.277543] [<ffffffff8106302d>] process_one_work+0x1cd/0x6a0
[ 60.277552] [<ffffffff81063d31>] worker_thread+0x121/0x3a0
[ 60.277560] [<ffffffff8106ae2b>] kthread+0xdb/0xe0
[ 60.277569] [<ffffffff815bb96c>] ret_from_fork+0x7c/0xb0
[ 60.277580] -> #1 (&j_cdbs->timer_mutex){+.+...}:
[ 60.277592] [<ffffffff810ac6d4>] lock_acquire+0xa4/0x200
[ 60.277600] [<ffffffff815b6157>] mutex_lock_nested+0x67/0x410
[ 60.277608] [<ffffffff814b785d>] cs_dbs_timer+0x8d/0xe0
[ 60.277616] [<ffffffff8106302d>] process_one_work+0x1cd/0x6a0
[ 60.277624] [<ffffffff81063d31>] worker_thread+0x121/0x3a0
[ 60.277633] [<ffffffff8106ae2b>] kthread+0xdb/0xe0
[ 60.277640] [<ffffffff815bb96c>] ret_from_fork+0x7c/0xb0
[ 60.277649] -> #0 ((&(&j_cdbs->work)->work)){+.+...}:
[ 60.277661] [<ffffffff810ab826>] __lock_acquire+0x1766/0x1d30
[ 60.277669] [<ffffffff810ac6d4>] lock_acquire+0xa4/0x200
[ 60.277677] [<ffffffff810621ed>] flush_work+0x3d/0x280
[ 60.277685] [<ffffffff81062d8a>] __cancel_work_timer+0x8a/0x120
[ 60.277693] [<ffffffff81062e53>] cancel_delayed_work_sync+0x13/0x20
[ 60.277701] [<ffffffff814b89d9>] cpufreq_governor_dbs+0x529/0x6f0
[ 60.277709] [<ffffffff814b76a7>] cs_cpufreq_governor_dbs+0x17/0x20
[ 60.277719] [<ffffffff814b5df8>] __cpufreq_governor+0x48/0x100
[ 60.277728] [<ffffffff814b6b80>] __cpufreq_remove_dev.isra.14+0x80/0x3c0
[ 60.277737] [<ffffffff815adc0d>] cpufreq_cpu_callback+0x38/0x4c
[ 60.277747] [<ffffffff81071a4d>] notifier_call_chain+0x5d/0x110
[ 60.277759] [<ffffffff81071b0e>] __raw_notifier_call_chain+0xe/0x10
[ 60.277768] [<ffffffff815a0a68>] _cpu_down+0x88/0x330
[ 60.277779] [<ffffffff815a0d46>] cpu_down+0x36/0x50
[ 60.277788] [<ffffffff815a2748>] store_online+0x98/0xd0
[ 60.277796] [<ffffffff81452a28>] dev_attr_store+0x18/0x30
[ 60.277806] [<ffffffff811d9edb>] sysfs_write_file+0xdb/0x150
[ 60.277818] [<ffffffff8116806d>] vfs_write+0xbd/0x1f0
[ 60.277826] [<ffffffff811686fc>] SyS_write+0x4c/0xa0
[ 60.277834] [<ffffffff815bbbbe>] tracesys+0xd0/0xd5
[ 60.277842] other info that might help us debug this:

[ 60.277848] Chain exists of:
(&(&j_cdbs->work)->work) --> &j_cdbs->timer_mutex --> cpu_hotplug.lock

[ 60.277864] Possible unsafe locking scenario:

[ 60.277869] CPU0 CPU1
[ 60.277873] ---- ----
[ 60.277877] lock(cpu_hotplug.lock);
[ 60.277885] lock(&j_cdbs->timer_mutex);
[ 60.277892] lock(cpu_hotplug.lock);
[ 60.277900] lock((&(&j_cdbs->work)->work));
[ 60.277907] *** DEADLOCK ***

[ 60.277915] 6 locks held by bash/2225:
[ 60.277919] #0: (sb_writers#6){.+.+.+}, at: [<ffffffff81168173>] vfs_write+0x1c3/0x1f0
[ 60.277937] #1: (&buffer->mutex){+.+.+.}, at: [<ffffffff811d9e3c>] sysfs_write_file+0x3c/0x150
[ 60.277954] #2: (s_active#61){.+.+.+}, at: [<ffffffff811d9ec3>] sysfs_write_file+0xc3/0x150
[ 60.277972] #3: (x86_cpu_hotplug_driver_mutex){+.+...}, at: [<ffffffff81024cf7>] cpu_hotplug_driver_lock+0x17/0x20
[ 60.277990] #4: (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff815a0d32>] cpu_down+0x22/0x50
[ 60.278007] #5: (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff81042d8b>] cpu_hotplug_begin+0x2b/0x60
[ 60.278023] stack backtrace:
[ 60.278031] CPU: 3 PID: 2225 Comm: bash Not tainted 3.10.0-rc7-dbg-01385-g241fd04-dirty #1744
[ 60.278037] Hardware name: Acer Aspire 5741G /Aspire 5741G , BIOS V1.20 02/08/2011
[ 60.278042] ffffffff8204e110 ffff88014df6b9f8 ffffffff815b3d90 ffff88014df6ba38
[ 60.278055] ffffffff815b0a8d ffff880150ed3f60 ffff880150ed4770 3871c4002c8980b2
[ 60.278068] ffff880150ed4748 ffff880150ed4770 ffff880150ed3f60 ffff88014df6bb00
[ 60.278081] Call Trace:
[ 60.278091] [<ffffffff815b3d90>] dump_stack+0x19/0x1b
[ 60.278101] [<ffffffff815b0a8d>] print_circular_bug+0x2b6/0x2c5
[ 60.278111] [<ffffffff810ab826>] __lock_acquire+0x1766/0x1d30
[ 60.278123] [<ffffffff81067e08>] ? __kernel_text_address+0x58/0x80
[ 60.278134] [<ffffffff810ac6d4>] lock_acquire+0xa4/0x200
[ 60.278142] [<ffffffff810621b5>] ? flush_work+0x5/0x280
[ 60.278151] [<ffffffff810621ed>] flush_work+0x3d/0x280
[ 60.278159] [<ffffffff810621b5>] ? flush_work+0x5/0x280
[ 60.278169] [<ffffffff810a9b14>] ? mark_held_locks+0x94/0x140
[ 60.278178] [<ffffffff81062d77>] ? __cancel_work_timer+0x77/0x120
[ 60.278188] [<ffffffff810a9cbd>] ? trace_hardirqs_on_caller+0xfd/0x1c0
[ 60.278196] [<ffffffff81062d8a>] __cancel_work_timer+0x8a/0x120
[ 60.278206] [<ffffffff81062e53>] cancel_delayed_work_sync+0x13/0x20
[ 60.278214] [<ffffffff814b89d9>] cpufreq_governor_dbs+0x529/0x6f0
[ 60.278225] [<ffffffff814b76a7>] cs_cpufreq_governor_dbs+0x17/0x20
[ 60.278234] [<ffffffff814b5df8>] __cpufreq_governor+0x48/0x100
[ 60.278244] [<ffffffff814b6b80>] __cpufreq_remove_dev.isra.14+0x80/0x3c0
[ 60.278255] [<ffffffff815adc0d>] cpufreq_cpu_callback+0x38/0x4c
[ 60.278265] [<ffffffff81071a4d>] notifier_call_chain+0x5d/0x110
[ 60.278275] [<ffffffff81071b0e>] __raw_notifier_call_chain+0xe/0x10
[ 60.278284] [<ffffffff815a0a68>] _cpu_down+0x88/0x330
[ 60.278292] [<ffffffff81024cf7>] ? cpu_hotplug_driver_lock+0x17/0x20
[ 60.278302] [<ffffffff815a0d46>] cpu_down+0x36/0x50
[ 60.278311] [<ffffffff815a2748>] store_online+0x98/0xd0
[ 60.278320] [<ffffffff81452a28>] dev_attr_store+0x18/0x30
[ 60.278329] [<ffffffff811d9edb>] sysfs_write_file+0xdb/0x150
[ 60.278337] [<ffffffff8116806d>] vfs_write+0xbd/0x1f0
[ 60.278347] [<ffffffff81185950>] ? fget_light+0x320/0x4b0
[ 60.278355] [<ffffffff811686fc>] SyS_write+0x4c/0xa0
[ 60.278364] [<ffffffff815bbbbe>] tracesys+0xd0/0xd5
[ 60.280582] smpboot: CPU 1 is now offline

The intention of that commit was to avoid warnings during CPU
hotplug, which indicated that offline CPUs were getting IPIs from the
cpufreq governor's work items. But the real root-cause of that
problem was commit a66b2e5 (cpufreq: Preserve sysfs files across
suspend/resume) because it totally skipped all the cpufreq callbacks
during CPU hotplug in the suspend/resume path, and hence it never
actually shut down the cpufreq governor's worker threads during CPU
offline in the suspend/resume path.

Reflecting back, the reason why we never suspected that commit as the
root-cause earlier, was that the original issue was reported with
just the halt command and nobody had brought in suspend/resume to the
equation.

The reason for _that_ in turn, as it turns out, is that earlier
halt/shutdown was being done by disabling non-boot CPUs while tasks
were frozen, just like suspend/resume.... but commit cf7df378a
(reboot: migrate shutdown/reboot to boot cpu) which came somewhere
along that very same time changed that logic: shutdown/halt no longer
takes CPUs offline. Thus, the test-cases for reproducing the bug
were vastly different and thus we went totally off the trail.

Overall, it was one hell of a confusion with so many commits
affecting each other and also affecting the symptoms of the problems
in subtle ways. Finally, now since the original problematic commit
(a66b2e5) has been completely reverted, revert this intermediate fix
too (2f7021a8), to fix the CPU hotplug deadlock. Phew!

Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Tested-by: Peter Wu <lekensteyn@gmail.com>
Cc: 3.10+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: don't leave stale policy pointer in cdbs->cur_policy

Clear ->cur_policy when stopping a governor, or the ->cur_policy
pointer may be stale on systems with have_governor_per_policy when a
new policy is allocated due to CPU hotplug offline/online.

[rjw: Changelog]
Suggested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: protect 'policy->cpus' from offlining during __gov_queue_work()

Jiri Kosina <jkosina@suse.cz> and Borislav Petkov <bp@alien8.de>
reported the warning:

[ 51.616759] ------------[ cut here ]------------
[ 51.621460] WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule+0x58/0x60()
[ 51.629638] Modules linked in: ext2 vfat fat loop snd_hda_codec_hdmi usbhid snd_hda_codec_realtek coretemp kvm_intel kvm snd_hda_intel snd_hda_codec crc32_pclmul crc32c_intel ghash_clmulni_intel snd_hwdep snd_pcm aesni_intel sb_edac aes_x86_64 ehci_pci snd_page_alloc glue_helper snd_timer xhci_hcd snd iTCO_wdt iTCO_vendor_support ehci_hcd edac_core lpc_ich acpi_cpufreq lrw gf128mul ablk_helper cryptd mperf usbcore usb_common soundcore mfd_core dcdbas evdev pcspkr processor i2c_i801 button microcode
[ 51.675581] CPU: 0 PID: 244 Comm: kworker/1:1 Tainted: G W 3.10.0-rc1+ #10
[ 51.683407] Hardware name: Dell Inc. Precision T3600/0PTTT9, BIOS A08 01/24/2013
[ 51.690901] Workqueue: events od_dbs_timer
[ 51.695069] 0000000000000009 ffff88043a2f5b68 ffffffff8161441c ffff88043a2f5ba8
[ 51.702602] ffffffff8103e540 0000000000000033 0000000000000001 ffff88043d5f8000
[ 51.710136] 00000000ffff0ce1 0000000000000001 ffff88044fc4fc08 ffff88043a2f5bb8
[ 51.717691] Call Trace:
[ 51.720191] [<ffffffff8161441c>] dump_stack+0x19/0x1b
[ 51.725396] [<ffffffff8103e540>] warn_slowpath_common+0x70/0xa0
[ 51.731473] [<ffffffff8103e58a>] warn_slowpath_null+0x1a/0x20
[ 51.737378] [<ffffffff81025628>] native_smp_send_reschedule+0x58/0x60
[ 51.744013] [<ffffffff81072cfd>] wake_up_nohz_cpu+0x2d/0xa0
[ 51.749745] [<ffffffff8104f6bf>] add_timer_on+0x8f/0x110
[ 51.755214] [<ffffffff8105f6fe>] __queue_delayed_work+0x16e/0x1a0
[ 51.761470] [<ffffffff8105f251>] ? try_to_grab_pending+0xd1/0x1a0
[ 51.767724] [<ffffffff8105f78a>] mod_delayed_work_on+0x5a/0xa0
[ 51.773719] [<ffffffff814f6b5d>] gov_queue_work+0x4d/0xc0
[ 51.779271] [<ffffffff814f60cb>] od_dbs_timer+0xcb/0x170
[ 51.784734] [<ffffffff8105e75d>] process_one_work+0x1fd/0x540
[ 51.790634] [<ffffffff8105e6f2>] ? process_one_work+0x192/0x540
[ 51.796711] [<ffffffff8105ef22>] worker_thread+0x122/0x380
[ 51.802350] [<ffffffff8105ee00>] ? rescuer_thread+0x320/0x320
[ 51.808264] [<ffffffff8106634a>] kthread+0xea/0xf0
[ 51.813200] [<ffffffff81066260>] ? flush_kthread_worker+0x150/0x150
[ 51.819644] [<ffffffff81623d5c>] ret_from_fork+0x7c/0xb0
[ 51.918165] nouveau E[ DRM] GPU lockup - switching to software fbcon
[ 51.930505] [<ffffffff81066260>] ? flush_kthread_worker+0x150/0x150
[ 51.936994] ---[ end trace f419538ada83b5c5 ]---

It was caused by the policy->cpus changed during the process of
__gov_queue_work(), in other word, cpu offline happened.

Use get/put_online_cpus() to prevent the offline from happening while
__gov_queue_work() is running.

[rjw: The problem has been present since recent commit 031299b
(cpufreq: governors: Avoid unnecessary per cpu timer interrupts)]

References: https://lkml.org/lkml/2013/6/5/88
Reported-by: Borislav Petkov <bp@alien8.de>
Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Don't create empty /sys/devices/system/cpu/cpufreq directory

When we don't have any file in cpu/cpufreq directory we shouldn't
create it. Specially with the introduction of per-policy governor
instance patchset, even governors are moved to
cpu/cpu*/cpufreq/governor-name directory and so this directory is
just not required.

Lets have it only when required.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Move get_cpu_idle_time() to cpufreq.c

Governors other than ondemand and conservative can also use
get_cpu_idle_time() and they aren't required to compile
cpufreq_governor.c. So, move these independent routines to
cpufreq.c instead.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Move get_governor_parent_kobj() to cpufreq.c

get_governor_parent_kobj() can be used by any governor, generic
cpufreq governors or platform specific ones and so must be present in
cpufreq.c instead of cpufreq_governor.c.

This patch moves it to cpufreq.c. This also adds
EXPORT_SYMBOL_GPL(get_governor_parent_kobj) so that modules can use
this function too.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Fix CPUFREQ_GOV_POLICY_{INIT|EXIT} notifiers

There are two types of INIT/EXIT activities that we need to do for
governors:
- Done only once per governor (doesn't depend how many instances of
the governor there are). eg: cpufreq_register_notifier() for
conservative governor.
- Done per governor instance, eg: sysfs_{create|remove}_group().

There were some corner cases where current code isn't able to handle
them separately and so failing for some test cases.

We use two separate variables now for keeping track of above two
requirements.
- governor->initialized for first one
- dbs_data->usage_count for per governor instance

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Calculate iowait time only when necessary

Currently we always calculate the CPU iowait time and add it to idle time.
If we are in ondemand and we use io_is_busy, we re-calculate iowait time
and we subtract it from idle time.

With this patch iowait time is calculated only when necessary avoiding
the double call to get_cpu_iowait_time_us. We use a parameter in
function get_cpu_idle_time to distinguish when the iowait time will be
added to idle time or not, without the need of keeping the prev_io_wait.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.,org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Avoid unnecessary per cpu timer interrupts

Following patch has introduced per cpu timers or works for ondemand and
conservative governors.

commit 2abfa876f1117b0ab45f191fb1f82c41b1cbc8fe
Author: Rickard Andersson <rickard.andersson@stericsson.com>
Date: Thu Dec 27 14:55:38 2012 +0000

cpufreq: handle SW coordinated CPUs

This causes additional unnecessary interrupts on all cpus when the load is
recently evaluated by any other cpu. i.e. When load is recently evaluated by cpu
x, we don't really need any other cpu to evaluate this load again for the next
sampling_rate time.

Some sort of code is present to avoid that but we are still getting timer
interrupts for all cpus. A good way of avoiding this would be to modify delays
for all cpus (policy->cpus) whenever any cpu has evaluated load.

This patch does this change and some related code cleanup.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governor: Implement per policy instances of governors

Currently, there can't be multiple instances of single governor_type.
If we have a multi-package system, where we have multiple instances
of struct policy (per package), we can't have multiple instances of
same governor. i.e. We can't have multiple instances of ondemand
governor for multiple packages.

Governors directory in sysfs is created at /sys/devices/system/cpu/cpufreq/
governor-name/. Which again reflects that there can be only one
instance of a governor_type in the system.

This is a bottleneck for multicluster system, where we want different
packages to use same governor type, but with different tunables.

This patch uses the infrastructure provided by earlier patch and
implements init/exit routines for ondemand and conservative
governors.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Fix WARN_ON() for multi-policy platforms

On multi-policy systems there is a single instance of governor for both the
policies (if same governor is chosen for both policies). With the code update
from following patches:

8eeed09 cpufreq: governors: Get rid of dbs_data->enable field
b394058 cpufreq: governors: Reset tunables only for cpufreq_unregister_governor()

We are creating/removing sysfs directory of governor for for every call to
GOV_START and STOP. This would fail for multi-policy system as there is a
per-policy call to START/STOP.

This patch reuses the governor->initialized variable to detect total users of
governor.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Don't check cpu_online(policy->cpu)

policy->cpu or cpus in policy->cpus can't be offline anymore. And so we don't
need to check if they are online or not.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Reset tunables only for cpufreq_unregister_governor()

Currently, whenever governor->governor() is called for CPUFRREQ_GOV_START event
we reset few tunables of governor. Which isn't correct, as this routine is
called for every cpu hot-[un]plugging event. We should actually be resetting
these only when the governor module is removed and re-installed.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Remove code redundancy between governors

With the inclusion of following patches:

9f4eb10 cpufreq: conservative: call dbs_check_cpu only when necessary
772b4b1 cpufreq: ondemand: call dbs_check_cpu only when necessary

code redundancy between the conservative and ondemand governors is
introduced again, so get rid of it.

[rjw: Changelog]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Get rid of dbs_data->enable field

CPUFREQ_GOV_START/STOP are called only once for all policy->cpus and hence we
don't need to adapt cpufreq_governor_dbs() routine for multiple calls.

So, this patch removes dbs_data->enable field entirely. And rearrange code a
bit.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: fix misuse of cdbs.cpu

Fix governors code to set all cpu's cdbs->cpu to the the actual cpu id
and use cur_policy->cpu istead of cdbs->cpu to track current governor's
leader cpu.

Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: implement generic policy_is_shared

Implement a generic helper function policy_is_shared() to replace the
current dbs_sw_coordinated_cpus() at cpufreq level, so that it can be
used by code other than cpufreq governors.

Suggested-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: clean timer init and exit code

Drop unused arguments from dbs_timer_init and clean dbs_timer_exit and
cpufreq_governor_dbs to remove non necessary special cases.

Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: ondemand: call dbs_check_cpu only when necessary

Modify ondemand timer to not resample CPU utilization if recently
sampled from another SW coordinated core.

Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: handle SW coordinated CPUs

This patch fixes a bug that occurred when we had load on a secondary CPU
and the primary CPU was sleeping. Only one sampling timer was spawned
and it was spawned as a deferred timer on the primary CPU, so when a
secondary CPU had a change in load this was not detected by the cpufreq
governor (both ondemand and conservative).

This patch make sure that deferred timers are run on all CPUs in the
case of software controlled CPUs that run on the same frequency.

Signed-off-by: Rickard Andersson <rickard.andersson@stericsson.com>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: Fix jiffies/cputime mixup (revisited)

This change was made by commit 8636fd2 (cpufreq: fix jiffies/cputime
mixup in conservative/ondemand governors) before, but then it has
been reverted inadvertently by commit 4471a34 (cpufreq: governors:
remove redundant code).

The changelog of commit 8636fd2's says:

The function get_cpu_idle_time_jiffy in both the conservative and
ondemand governors use jiffies_to_usecs to convert a cputime value
to usecs which gives the wrong value on architectures where cputime
and jiffies use different units. Only matters if NO_HZ is
disabled, since otherwise get_cpu_idle_time_us should already
return a valid value, and get_cpu_idle_time_jiffy isn't actually
called.

Since now we have only one common get_cpu_idle_time_jiffy() used by
both governors in question, modify it along the lines of commit
8636fd2 to restore the correct behavior.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>

cpufreq: Fix sparse warnings by updating cputime64_t to u64

There were few sparse warnings due to mismatch of type on function arguments.
Two types were used u64 and cputime64_t. Both are actually u64, so use u64 only.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: governors: remove redundant code

Initially ondemand governor was written and then using its code conservative
governor is written. It used a lot of code from ondemand governor, but copy of
code was created instead of using the same routines from both governors. Which
increased code redundancy, which is difficult to manage.

This patch is an attempt to move common part of both the governors to
cpufreq_governor.c file to come over above mentioned issues.

This shouldn't change anything from functionality point of view.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: fix jiffies/cputime mixup in conservative/ondemand governors

The function get_cpu_idle_time_jiffy in both the conservative and
ondemand governors use jiffies_to_usecs to convert a cputime value to
usecs which gives the wrong value on architectures where cputime and
jiffies use different units. Only matters if NO_HZ is disabled, since
otherwise get_cpu_idle_time_us should already return a valid value, and
get_cpu_idle_time_jiffy isn't actually called.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

cpufreq: Move common part from governors to separate file, v2

Multiple cpufreq governers have defined similar get_cpu_idle_time_***()
routines. These routines must be moved to some common place, so that all
governors can use them.

So moving them to cpufreq_governor.c, which seems to be a better place for
keeping these routines.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>