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Date: Mon, 01 Jul 2013 12:42:01 +0800
From: Michael Wang <wangyun@...ux.vnet.ibm.com>
To: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
CC: Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...en8.de>,
"Rafael J. Wysocki" <rjw@...k.pl>,
Viresh Kumar <viresh.kumar@...aro.org>,
"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
linux-pm@...r.kernel.org
Subject: Re: [LOCKDEP] cpufreq: possible circular locking dependency detected
Hi, Sergey
On 06/26/2013 05:15 AM, Sergey Senozhatsky wrote:
[snip]
>
> [ 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 ***
It may caused by that 'j_cdbs->work.work' and 'j_cdbs->timer_mutex'
has the same lock class, although they are different lock...
This may help fix the issue:
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 5af40ad..aa05eaa 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c
@@ -229,6 +229,8 @@ static void set_sampling_rate(struct dbs_data *dbs_data,
}
}
+static struct lock_class_key j_cdbs_key;
+
int cpufreq_governor_dbs(struct cpufreq_policy *policy,
struct common_dbs_data *cdata, unsigned int event)
{
@@ -366,6 +368,8 @@ int (struct cpufreq_policy *policy,
kcpustat_cpu(j).cpustat[CPUTIME_NICE];
mutex_init(&j_cdbs->timer_mutex);
+ lockdep_set_class(&j_cdbs->timer_mutex, &j_cdbs_key);
+
INIT_DEFERRABLE_WORK(&j_cdbs->work,
dbs_data->cdata->gov_dbs_timer);
}
Would you like to take a try?
Regards,
Michael Wang
>
> [ 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
>
>
> -ss
>
> --
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