linux-kernel - Re: [PATCH] sched: fix tsk->pi_lock isn't held when do_set_cpus

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Date:	Tue, 25 Aug 2015 16:38:14 +0800
From:	Wanpeng Li <wanpeng.li@...mail.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Leo Yan <leo.yan@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: fix tsk->pi_lock isn't held when
 do_set_cpus_allowed()

On 8/25/15 4:30 PM, Ingo Molnar wrote:
> * Wanpeng Li <wanpeng.li@...mail.com> wrote:
>
>>>> --- a/kernel/cpuset.c
>>>> +++ b/kernel/cpuset.c
>>>> @@ -2376,8 +2376,12 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
>>>>   void cpuset_cpus_allowed_fallback(struct task_struct *tsk)
>>>>   {
>>>> +	unsigned long flags;
>>>> +
>>>>   	rcu_read_lock();
>>>> +	raw_spin_lock_irqsave(&tsk->pi_lock, flags);
>>>>   	do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus);
>>>> +	raw_spin_lock_irqsave(&tsk->pi_lock, flags);
>>> Just curious, Will introduce deadlock after acquire lock twice? ;)
>> Could you point out where acquires lock twice?
> In the code you quote?

Shame me, sorry for sending out the wrong version. I fix in it soon in v2.

Regards,
Wanpeng Li

>
> Thanks,
>
> 	Ingo

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