Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755227Ab3GOUtr (ORCPT ); Mon, 15 Jul 2013 16:49:47 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:61481 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754405Ab3GOUto (ORCPT ); Mon, 15 Jul 2013 16:49:44 -0400 From: Peter Wu To: "Srivatsa S. Bhat" Cc: Sergey Senozhatsky , Michael Wang , Jiri Kosina , Borislav Petkov , "Rafael J. Wysocki" , Viresh Kumar , linux-kernel@vger.kernel.org, cpufreq@vger.kernel.org, linux-pm@vger.kernel.org, Bartlomiej Zolnierkiewicz Subject: Re: [LOCKDEP] cpufreq: possible circular locking dependency detected Date: Mon, 15 Jul 2013 22:49:38 +0200 Message-ID: <3163965.oDB9vd9ImG@al> User-Agent: KMail/4.10.5 (Linux/3.10.0-1-custom; KDE/4.10.5; x86_64; ; ) In-Reply-To: <51E3F6EB.2050807@linux.vnet.ibm.com> References: <20130625211544.GA2270@swordfish> <20130715082918.GA2435@swordfish> <51E3F6EB.2050807@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 18693 Lines: 339 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: [] get_online_cpus+0x41/0x60 [ 71.204869] [ 71.204869] but task is already holding lock: [ 71.204870] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [] 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] [] lock_acquire+0x90/0x140 [ 71.204894] [] down_write+0x49/0x6b [ 71.204898] [] lock_policy_rwsem_write+0x39/0x40 [ 71.204901] [] cpufreq_update_policy+0x40/0x130 [ 71.204904] [] cpufreq_stat_cpu_callback+0x27/0x70 [ 71.204907] [] notifier_call_chain+0x4d/0x70 [ 71.204911] [] __raw_notifier_call_chain+0xe/0x10 [ 71.204915] [] __cpu_notify+0x20/0x40 [ 71.204918] [] _cpu_up+0x116/0x170 [ 71.204921] [] enable_nonboot_cpus+0x90/0xe0 [ 71.204926] [] suspend_devices_and_enter+0x301/0x420 [ 71.204930] [] pm_suspend+0x1d0/0x230 [ 71.205000] [] state_store+0x8a/0x100 [ 71.205005] [] kobj_attr_store+0xf/0x30 [ 71.205009] [] sysfs_write_file+0xe6/0x170 [ 71.205014] [] vfs_write+0xce/0x200 [ 71.205018] [] SyS_write+0x55/0xa0 [ 71.205022] [] system_call_fastpath+0x16/0x1b [ 71.205025] -> #0 (cpu_hotplug.lock){+.+.+.}: [ 71.205093] [] __lock_acquire+0x174c/0x1ed0 [ 71.205096] [] lock_acquire+0x90/0x140 [ 71.205099] [] mutex_lock_nested+0x70/0x380 [ 71.205102] [] get_online_cpus+0x41/0x60 [ 71.205217] [] gov_queue_work+0x28/0xc0 [ 71.205221] [] cpufreq_governor_dbs+0x507/0x710 [ 71.205224] [] od_cpufreq_governor_dbs+0x17/0x20 [ 71.205226] [] __cpufreq_governor+0x87/0x1c0 [ 71.205230] [] __cpufreq_set_policy+0x1b5/0x1e0 [ 71.205232] [] store_scaling_governor+0xea/0x1f0 [ 71.205235] [] store+0x6d/0xc0 [ 71.205238] [] sysfs_write_file+0xe6/0x170 [ 71.205305] [] vfs_write+0xce/0x200 [ 71.205308] [] SyS_write+0x55/0xa0 [ 71.205311] [] 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: [] vfs_write+0x1d3/0x200 [ 71.205520] #1: (&buffer->mutex){+.+.+.}, at: [] sysfs_write_file+0x44/0x170 [ 71.205640] #2: (s_active#178){.+.+.+}, at: [] sysfs_write_file+0xcd/0x170 [ 71.205648] #3: (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [] 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] [] dump_stack+0x55/0x76 [ 71.205907] [] print_circular_bug+0x1fb/0x20c [ 71.205910] [] __lock_acquire+0x174c/0x1ed0 [ 71.205913] [] ? __lock_acquire+0x3fc/0x1ed0 [ 71.205916] [] ? get_online_cpus+0x41/0x60 [ 71.205919] [] lock_acquire+0x90/0x140 [ 71.205921] [] ? get_online_cpus+0x41/0x60 [ 71.205924] [] mutex_lock_nested+0x70/0x380 [ 71.205927] [] ? get_online_cpus+0x41/0x60 [ 71.205930] [] ? mark_held_locks+0x7e/0x150 [ 71.205933] [] ? mutex_unlock+0xe/0x10 [ 71.205936] [] ? __mutex_unlock_slowpath+0xd1/0x180 [ 71.205938] [] get_online_cpus+0x41/0x60 [ 71.205941] [] gov_queue_work+0x28/0xc0 [ 71.205944] [] cpufreq_governor_dbs+0x507/0x710 [ 71.205947] [] od_cpufreq_governor_dbs+0x17/0x20 [ 71.205950] [] __cpufreq_governor+0x87/0x1c0 [ 71.206009] [] __cpufreq_set_policy+0x1b5/0x1e0 [ 71.206012] [] store_scaling_governor+0xea/0x1f0 [ 71.206014] [] ? cpufreq_update_policy+0x130/0x130 [ 71.206018] [] ? lock_policy_rwsem_write+0x39/0x40 [ 71.206021] [] store+0x6d/0xc0 [ 71.206024] [] sysfs_write_file+0xe6/0x170 [ 71.206026] [] vfs_write+0xce/0x200 [ 71.206029] [] SyS_write+0x55/0xa0 [ 71.206032] [] 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). 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 > 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) I ran six times `pm-suspend` without any lockdep warnings. I reverted a66b2e5 and 2f7021a8 on top of current master (47188d3). Regards, Peter > 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: [] > flush_work+0x5/0x280 [ 60.277444] but task is already holding lock: > [ 60.277449] (cpu_hotplug.lock){+.+.+.}, at: [] > 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] [] lock_acquire+0xa4/0x200 > [ 60.277503] [] mutex_lock_nested+0x67/0x410 > [ 60.277514] [] get_online_cpus+0x3c/0x60 > [ 60.277522] [] gov_queue_work+0x2a/0xb0 > [ 60.277532] [] cs_dbs_timer+0xc1/0xe0 > [ 60.277543] [] process_one_work+0x1cd/0x6a0 > [ 60.277552] [] worker_thread+0x121/0x3a0 > [ 60.277560] [] kthread+0xdb/0xe0 > [ 60.277569] [] ret_from_fork+0x7c/0xb0 > [ 60.277580] -> #1 (&j_cdbs->timer_mutex){+.+...}: > [ 60.277592] [] lock_acquire+0xa4/0x200 > [ 60.277600] [] mutex_lock_nested+0x67/0x410 > [ 60.277608] [] cs_dbs_timer+0x8d/0xe0 > [ 60.277616] [] process_one_work+0x1cd/0x6a0 > [ 60.277624] [] worker_thread+0x121/0x3a0 > [ 60.277633] [] kthread+0xdb/0xe0 > [ 60.277640] [] ret_from_fork+0x7c/0xb0 > [ 60.277649] -> #0 ((&(&j_cdbs->work)->work)){+.+...}: > [ 60.277661] [] __lock_acquire+0x1766/0x1d30 > [ 60.277669] [] lock_acquire+0xa4/0x200 > [ 60.277677] [] flush_work+0x3d/0x280 > [ 60.277685] [] __cancel_work_timer+0x8a/0x120 > [ 60.277693] [] > cancel_delayed_work_sync+0x13/0x20 [ 60.277701] > [] cpufreq_governor_dbs+0x529/0x6f0 [ 60.277709] > [] cs_cpufreq_governor_dbs+0x17/0x20 [ 60.277719] > [] __cpufreq_governor+0x48/0x100 [ 60.277728] > [] __cpufreq_remove_dev.isra.14+0x80/0x3c0 [ 60.277737] > [] cpufreq_cpu_callback+0x38/0x4c [ 60.277747] > [] notifier_call_chain+0x5d/0x110 [ 60.277759] > [] __raw_notifier_call_chain+0xe/0x10 [ 60.277768] > [] _cpu_down+0x88/0x330 > [ 60.277779] [] cpu_down+0x36/0x50 > [ 60.277788] [] store_online+0x98/0xd0 > [ 60.277796] [] dev_attr_store+0x18/0x30 > [ 60.277806] [] sysfs_write_file+0xdb/0x150 > [ 60.277818] [] vfs_write+0xbd/0x1f0 > [ 60.277826] [] SyS_write+0x4c/0xa0 > [ 60.277834] [] 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: [] > vfs_write+0x1c3/0x1f0 [ 60.277937] #1: (&buffer->mutex){+.+.+.}, at: > [] sysfs_write_file+0x3c/0x150 [ 60.277954] #2: > (s_active#61){.+.+.+}, at: [] sysfs_write_file+0xc3/0x150 > [ 60.277972] #3: (x86_cpu_hotplug_driver_mutex){+.+...}, at: > [] cpu_hotplug_driver_lock+0x17/0x20 [ 60.277990] #4: > (cpu_add_remove_lock){+.+.+.}, at: [] cpu_down+0x22/0x50 > [ 60.278007] #5: (cpu_hotplug.lock){+.+.+.}, at: [] > 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] [] dump_stack+0x19/0x1b > [ 60.278101] [] print_circular_bug+0x2b6/0x2c5 > [ 60.278111] [] __lock_acquire+0x1766/0x1d30 > [ 60.278123] [] ? __kernel_text_address+0x58/0x80 > [ 60.278134] [] lock_acquire+0xa4/0x200 > [ 60.278142] [] ? flush_work+0x5/0x280 > [ 60.278151] [] flush_work+0x3d/0x280 > [ 60.278159] [] ? flush_work+0x5/0x280 > [ 60.278169] [] ? mark_held_locks+0x94/0x140 > [ 60.278178] [] ? __cancel_work_timer+0x77/0x120 > [ 60.278188] [] ? trace_hardirqs_on_caller+0xfd/0x1c0 > [ 60.278196] [] __cancel_work_timer+0x8a/0x120 > [ 60.278206] [] cancel_delayed_work_sync+0x13/0x20 > [ 60.278214] [] cpufreq_governor_dbs+0x529/0x6f0 > [ 60.278225] [] cs_cpufreq_governor_dbs+0x17/0x20 > [ 60.278234] [] __cpufreq_governor+0x48/0x100 > [ 60.278244] [] __cpufreq_remove_dev.isra.14+0x80/0x3c0 > [ 60.278255] [] cpufreq_cpu_callback+0x38/0x4c [ > 60.278265] [] notifier_call_chain+0x5d/0x110 [ > 60.278275] [] __raw_notifier_call_chain+0xe/0x10 [ > 60.278284] [] _cpu_down+0x88/0x330 > [ 60.278292] [] ? cpu_hotplug_driver_lock+0x17/0x20 > [ 60.278302] [] cpu_down+0x36/0x50 > [ 60.278311] [] store_online+0x98/0xd0 > [ 60.278320] [] dev_attr_store+0x18/0x30 > [ 60.278329] [] sysfs_write_file+0xdb/0x150 > [ 60.278337] [] vfs_write+0xbd/0x1f0 > [ 60.278347] [] ? fget_light+0x320/0x4b0 > [ 60.278355] [] SyS_write+0x4c/0xa0 > [ 60.278364] [] 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 > Reported-by: Bartlomiej Zolnierkiewicz > Signed-off-by: Srivatsa S. Bhat > --- > > 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 > #include > #include > -#include > > #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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/