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>
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>
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>
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>
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>
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>
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>
Following patch has introduced per cpu timers or works for ondemand and
conservative governors.
commit 2abfa876f1
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>
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>
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>
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>
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>
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_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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
Srivatsa S. Bhat