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 10:30:59 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Wanpeng Li <wanpeng.li@...mail.com>
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()


* 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?

Thanks,

	Ingo
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