linux-kernel - Re: [PATCH] sched/deadline/rtmutex: Fix a PI crash for deadline tasks

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Message-ID: <570DAB3F.4030501@redhat.com>
Date:	Wed, 13 Apr 2016 10:13:19 +0800
From:	Xunlei Pang <xpang@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Juri Lelli <juri.lelli@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] sched/deadline/rtmutex: Fix a PI crash for deadline tasks

On 2016/04/12 at 23:51, Peter Zijlstra wrote:
> On Tue, Apr 12, 2016 at 11:08:04AM +0800, Xunlei Pang wrote:
>> I spotted another issue, we access pi_task without any lock in enqueue_task_dl(),
> OK, so I'm on the road and entirely jetlagged, but how can
> enqueue_task_dl() not have rq->lock held?

It held current's rq->lock, but not holding pi_task's any lock, so pi_task's attributes
can change concurrently with subsequent pi_se->dl_runtime and pi_se->dl_period
access, and result in issues.

Regards,
Xunlei