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Message-ID: <20150604094043.GF3644@twins.programming.kicks-ass.net>
Date: Thu, 4 Jun 2015 11:40:43 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Fengguang Wu <fengguang.wu@...el.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>,
Ingo Molnar <mingo@...nel.org>,
kpreempt-tech@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
LKP <lkp@...org>
Subject: Re: [sched/preempt] BUG: kernel boot crashed
On Thu, Jun 04, 2015 at 12:55:36PM +0800, Fengguang Wu wrote:
> Greetings,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>
> commit b30f0e3ffedfa52b1d67a302ae5860c49998e5e2
> Author: Frederic Weisbecker <fweisbec@...il.com>
> AuthorDate: Tue May 12 16:41:49 2015 +0200
> Commit: Ingo Molnar <mingo@...nel.org>
> CommitDate: Tue May 19 08:39:12 2015 +0200
>
> sched/preempt: Optimize preemption operations on __schedule() callers
>
> __schedule() disables preemption and some of its callers
> (the preempt_schedule*() family) also set PREEMPT_ACTIVE.
>
> So we have two preempt_count() modifications that could be performed
> at once.
>
> Lets remove the preemption disablement from __schedule() and pull
> this responsibility to its callers in order to optimize preempt_count()
> operations in a single place.
>
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Link: http://lkml.kernel.org/r/1431441711-29753-5-git-send-email-fweisbec@gmail.com
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
Frederic said that he was working on the issue and we should expect
patches shortly.
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