linux-kernel - Re: [PATCH v2 07/12] sched: Robustify preemption leak checks

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Message-ID: <20150930053501.55ebe134@gandalf.local.home>
Date:	Wed, 30 Sep 2015 05:35:01 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, fweisbec@...il.com, oleg@...hat.com,
	umgwanakikbuti@...il.com, tglx@...utronix.de
Subject: Re: [PATCH v2 07/12] sched: Robustify preemption leak checks

On Wed, 30 Sep 2015 09:10:42 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

> When we warn about a preempt_count leak; reset the preempt_count to
> the known good value such that the problem does not ripple forward.
> 
> This is most important on x86 which has a per cpu preempt_count that is
> not saved/restored (after this series). So if you schedule with an
> invalid (!2*PREEMPT_DISABLE_OFFSET) preempt_count the next task is
> messed up too.
> 
> Enforcing this invariant limits the borkage to just the one task.
> 
> Reviewed-by: Frederic Weisbecker <fweisbec@...il.com>
> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---

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