Messages in this thread Patch in this message | | | Date | Tue, 9 Feb 2010 04:10:41 -0500 | From | Amerigo Wang <> | Subject | [Patch] cpufreq: fix a deadlock during shutting down |
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Benjamin reported that, the machine deadlocks right after printing the following when doing a shutdown:
halt/4071 is trying to acquire lock: (s_active){++++.+}, at: [<c0000000001ef868>] .sysfs_addrm_finish+0x58/0xc0
but task is already holding lock: (&per_cpu(cpu_policy_rwsem, cpu)){+.+.+.}, at: [<c0000000004cd6ac>] .lock_policy_rwsem_write+0x84/0xf4
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
<nothing else ... machine deadlocked here>
This is because we are trying to kobject_put() a kobject while we are holding cpu policy rwsem. So just move kobject_put() down after releasing the rwsem.
Totally untested.
Reported-by: Xiaotian Feng <xtfeng@gmail.com> Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: WANG Cong <amwang@redhat.com> Cc: Dave Jones <davej@redhat.com> Cc: Thomas Renninger <trenn@suse.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
--- diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 67bc2ec..222b35f 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1113,6 +1113,7 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) unsigned int cpu = sys_dev->id; unsigned long flags; struct cpufreq_policy *data; + struct kobject *kobj; #ifdef CONFIG_SMP struct sys_device *cpu_sys_dev; unsigned int j; @@ -1192,7 +1193,7 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) if (cpufreq_driver->target) __cpufreq_governor(data, CPUFREQ_GOV_STOP); - kobject_put(&data->kobj); + kobj = &data->kobj; /* we need to make sure that the underlying kobj is actually * not referenced anymore by anybody before we proceed with @@ -1207,6 +1208,7 @@ static int __cpufreq_remove_dev(struct sys_device *sys_dev) unlock_policy_rwsem_write(cpu); + kobject_put(kobj); free_cpumask_var(data->related_cpus); free_cpumask_var(data->cpus); kfree(data);
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