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SubjectRe: [LOCKDEP] cpufreq: possible circular locking dependency detected
Hi Peter,

On 07/16/2013 02:19 AM, Peter Wu wrote:
> Hi,
>
> I think I also encountered this similar issue after resume (and possibly a
> real deadlock yesterday before/during suspend?). One message:
>
> [ 71.204848] ======================================================
> [ 71.204850] [ INFO: possible circular locking dependency detected ]
> [ 71.204852] 3.11.0-rc1cold-00008-g47188d3 #1 Tainted: G W
> [ 71.204854] -------------------------------------------------------
> [ 71.204855] ondemand/2034 is trying to acquire lock:
> [ 71.204857] (cpu_hotplug.lock){+.+.+.}, at: [<ffffffff8104ba31>] get_online_cpus+0x41/0x60
> [ 71.204869]
> [ 71.204869] but task is already holding lock:
> [ 71.204870] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<ffffffff8151fba9>] lock_policy_rwsem_write+0x39/0x40
> [ 71.204879]
> [ 71.204879] which lock already depends on the new lock.
> [ 71.204879]
> [ 71.204881]
> [ 71.204881] the existing dependency chain (in reverse order) is:
> [ 71.204884]
> -> #1 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}:
> [ 71.204889] [<ffffffff810ac130>] lock_acquire+0x90/0x140
> [ 71.204894] [<ffffffff81660fe9>] down_write+0x49/0x6b
> [ 71.204898] [<ffffffff8151fba9>] lock_policy_rwsem_write+0x39/0x40
> [ 71.204901] [<ffffffff815213e0>] cpufreq_update_policy+0x40/0x130
> [ 71.204904] [<ffffffff81522327>] cpufreq_stat_cpu_callback+0x27/0x70
> [ 71.204907] [<ffffffff81668acd>] notifier_call_chain+0x4d/0x70
> [ 71.204911] [<ffffffff8107730e>] __raw_notifier_call_chain+0xe/0x10
> [ 71.204915] [<ffffffff8104b780>] __cpu_notify+0x20/0x40
> [ 71.204918] [<ffffffff8104b916>] _cpu_up+0x116/0x170
> [ 71.204921] [<ffffffff8164d540>] enable_nonboot_cpus+0x90/0xe0
> [ 71.204926] [<ffffffff81098bd1>] suspend_devices_and_enter+0x301/0x420
> [ 71.204930] [<ffffffff81098ec0>] pm_suspend+0x1d0/0x230
> [ 71.205000] [<ffffffff81097b2a>] state_store+0x8a/0x100
> [ 71.205005] [<ffffffff8131559f>] kobj_attr_store+0xf/0x30
> [ 71.205009] [<ffffffff811fac36>] sysfs_write_file+0xe6/0x170
> [ 71.205014] [<ffffffff81183c5e>] vfs_write+0xce/0x200
> [ 71.205018] [<ffffffff81184165>] SyS_write+0x55/0xa0
> [ 71.205022] [<ffffffff8166d3c2>] system_call_fastpath+0x16/0x1b
> [ 71.205025]
> -> #0 (cpu_hotplug.lock){+.+.+.}:
> [ 71.205093] [<ffffffff810ab35c>] __lock_acquire+0x174c/0x1ed0
> [ 71.205096] [<ffffffff810ac130>] lock_acquire+0x90/0x140
> [ 71.205099] [<ffffffff8165f7b0>] mutex_lock_nested+0x70/0x380
> [ 71.205102] [<ffffffff8104ba31>] get_online_cpus+0x41/0x60
> [ 71.205217] [<ffffffff815247f8>] gov_queue_work+0x28/0xc0
> [ 71.205221] [<ffffffff81524d97>] cpufreq_governor_dbs+0x507/0x710
> [ 71.205224] [<ffffffff81522a17>] od_cpufreq_governor_dbs+0x17/0x20
> [ 71.205226] [<ffffffff8151fec7>] __cpufreq_governor+0x87/0x1c0
> [ 71.205230] [<ffffffff81520445>] __cpufreq_set_policy+0x1b5/0x1e0
> [ 71.205232] [<ffffffff8152055a>] store_scaling_governor+0xea/0x1f0
> [ 71.205235] [<ffffffff8151fcbd>] store+0x6d/0xc0
> [ 71.205238] [<ffffffff811fac36>] sysfs_write_file+0xe6/0x170
> [ 71.205305] [<ffffffff81183c5e>] vfs_write+0xce/0x200
> [ 71.205308] [<ffffffff81184165>] SyS_write+0x55/0xa0
> [ 71.205311] [<ffffffff8166d3c2>] system_call_fastpath+0x16/0x1b
> [ 71.205313]
> [ 71.205313] other info that might help us debug this:
> [ 71.205313]
> [ 71.205315] Possible unsafe locking scenario:
> [ 71.205315]
> [ 71.205317] CPU0 CPU1
> [ 71.205318] ---- ----
> [ 71.205383] lock(&per_cpu(cpu_policy_rwsem, cpu));
> [ 71.205386] lock(cpu_hotplug.lock);
> [ 71.205389] lock(&per_cpu(cpu_policy_rwsem, cpu));
> [ 71.205392] lock(cpu_hotplug.lock);
> [ 71.205509]
> [ 71.205509] *** DEADLOCK ***
> [ 71.205509]
> [ 71.205511] 4 locks held by ondemand/2034:
> [ 71.205512] #0: (sb_writers#6){.+.+.+}, at: [<ffffffff81183d63>] vfs_write+0x1d3/0x200
> [ 71.205520] #1: (&buffer->mutex){+.+.+.}, at: [<ffffffff811fab94>] sysfs_write_file+0x44/0x170
> [ 71.205640] #2: (s_active#178){.+.+.+}, at: [<ffffffff811fac1d>] sysfs_write_file+0xcd/0x170
> [ 71.205648] #3: (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<ffffffff8151fba9>] lock_policy_rwsem_write+0x39/0x40
> [ 71.205655]
> [ 71.205655] stack backtrace:
> [ 71.205658] CPU: 1 PID: 2034 Comm: ondemand Tainted: G W 3.11.0-rc1cold-00008-g47188d3 #1
> [ 71.205660] Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./Z68X-UD3H-B3, BIOS U1l 03/08/2013
> [ 71.205773] ffffffff8218fd20 ffff8805fc5d38e8 ffffffff8165b74d 0000000000000000
> [ 71.205778] ffffffff8211f130 ffff8805fc5d3938 ffffffff81657cef ffffffff8218fd20
> [ 71.205783] ffff8805fc5d39c0 ffff8805fc5d3938 ffff880603726678 ffff880603725f10
> [ 71.205900] Call Trace:
> [ 71.205903] [<ffffffff8165b74d>] dump_stack+0x55/0x76
> [ 71.205907] [<ffffffff81657cef>] print_circular_bug+0x1fb/0x20c
> [ 71.205910] [<ffffffff810ab35c>] __lock_acquire+0x174c/0x1ed0
> [ 71.205913] [<ffffffff810aa00c>] ? __lock_acquire+0x3fc/0x1ed0
> [ 71.205916] [<ffffffff8104ba31>] ? get_online_cpus+0x41/0x60
> [ 71.205919] [<ffffffff810ac130>] lock_acquire+0x90/0x140
> [ 71.205921] [<ffffffff8104ba31>] ? get_online_cpus+0x41/0x60
> [ 71.205924] [<ffffffff8165f7b0>] mutex_lock_nested+0x70/0x380
> [ 71.205927] [<ffffffff8104ba31>] ? get_online_cpus+0x41/0x60
> [ 71.205930] [<ffffffff810a89ee>] ? mark_held_locks+0x7e/0x150
> [ 71.205933] [<ffffffff81660b9e>] ? mutex_unlock+0xe/0x10
> [ 71.205936] [<ffffffff8165fb91>] ? __mutex_unlock_slowpath+0xd1/0x180
> [ 71.205938] [<ffffffff8104ba31>] get_online_cpus+0x41/0x60
> [ 71.205941] [<ffffffff815247f8>] gov_queue_work+0x28/0xc0
> [ 71.205944] [<ffffffff81524d97>] cpufreq_governor_dbs+0x507/0x710
> [ 71.205947] [<ffffffff81522a17>] od_cpufreq_governor_dbs+0x17/0x20
> [ 71.205950] [<ffffffff8151fec7>] __cpufreq_governor+0x87/0x1c0
> [ 71.206009] [<ffffffff81520445>] __cpufreq_set_policy+0x1b5/0x1e0
> [ 71.206012] [<ffffffff8152055a>] store_scaling_governor+0xea/0x1f0
> [ 71.206014] [<ffffffff815214d0>] ? cpufreq_update_policy+0x130/0x130
> [ 71.206018] [<ffffffff8151fba9>] ? lock_policy_rwsem_write+0x39/0x40
> [ 71.206021] [<ffffffff8151fcbd>] store+0x6d/0xc0
> [ 71.206024] [<ffffffff811fac36>] sysfs_write_file+0xe6/0x170
> [ 71.206026] [<ffffffff81183c5e>] vfs_write+0xce/0x200
> [ 71.206029] [<ffffffff81184165>] SyS_write+0x55/0xa0
> [ 71.206032] [<ffffffff8166d3c2>] system_call_fastpath+0x16/0x1b
>
> (the other was with the locks acquired lock reversed, i.e. cpu_hotplug.lock
> was held on CPU0 and CPU1 tries to lock &per_cpu(...)). This one is tagged
> "ondemand", the other one "pm-suspend" (reproducable with a high probability).
>

Hmm, this looks like a different problem, where a store (echo from sysfs) to
the scaling_governor file races with suspend/resume. Can you please open a
new thread and post the bug report? (Otherwise this thread will get even more
confusing if we start discussing separate problems all in one single email
thread.)

> On Monday 15 July 2013 18:49:39 Srivatsa S. Bhat wrote:
>> I think I finally found out what exactly is going wrong! :-)
>>
>> I tried reproducing the problem on my machine, and found that the problem
>> (warning about IPIs to offline CPUs) happens *only* while doing
>> suspend/resume and not during halt/shutdown/reboot or regular CPU hotplug
>> via sysfs files. That got me thinking and I finally figured out that commit
>> a66b2e5 is again the culprit.
>>
>> So here is the solution:
>>
>> On 3.11-rc1, apply these patches in the order mentioned below, and check
>> whether it fixes _all_ problems (both the warnings about IPI as well as the
>> lockdep splat).
>>
>> 1. Patch given in: https://lkml.org/lkml/2013/7/11/661
>> (Just apply patch 1, not the entire patchset).
>>
>> 2. Apply the patch shown below, on top of the above patch:
>>
>> ---------------------------------------------------------------------------
>>
>>
>> From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>> Subject: [PATCH] cpufreq: Revert commit 2f7021a to fix CPU hotplug
>> regression
>
> Please use '2f7021a8', without the '8' the commit hash is ambiguous.
> (git describe says: v3.10-rc4-2-g2f7021a8)
>

Yeah, even I noticed it after I sent out the patch when I was trying to look
up that commit for some other reason. Thanks for pointing that out!

> I ran six times `pm-suspend` without any lockdep warnings. I reverted a66b2e5
> and 2f7021a8 on top of current master (47188d3).
>

Cool! Thanks for testing!

Regards,
Srivatsa S. Bhat

>
>> commit 2f7021a (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 intent of this 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, 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: rigrate 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 (2f7021a), 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>
>> ---
>>
>> drivers/cpufreq/cpufreq_governor.c | 3 ---
>> 1 file changed, 3 deletions(-)
>>
>> diff --git a/drivers/cpufreq/cpufreq_governor.c
>> b/drivers/cpufreq/cpufreq_governor.c index 4645876..7b839a8 100644
>> --- a/drivers/cpufreq/cpufreq_governor.c
>> +++ b/drivers/cpufreq/cpufreq_governor.c
>> @@ -25,7 +25,6 @@
>> #include <linux/slab.h>
>> #include <linux/types.h>
>> #include <linux/workqueue.h>
>> -#include <linux/cpu.h>
>>
>> #include "cpufreq_governor.h"
>>
>> @@ -137,10 +136,8 @@ void gov_queue_work(struct dbs_data *dbs_data, struct
>> cpufreq_policy *policy, if (!all_cpus) {
>> __gov_queue_work(smp_processor_id(), dbs_data, delay);
>> } else {
>> - get_online_cpus();
>> for_each_cpu(i, policy->cpus)
>> __gov_queue_work(i, dbs_data, delay);
>> - put_online_cpus();
>> }
>> }
>> EXPORT_SYMBOL_GPL(gov_queue_work);
>
>



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