linux-kernel - Re: [tip:core/urgent] sched_clock: Disable seqlock lockdep usage in sched

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Message-ID: <52D58D7F.2030306@linaro.org>
Date:	Tue, 14 Jan 2014 11:18:23 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	sboyd@...eaurora.org, w@....eu, khalasa@...p.pl,
	u.kleine-koenig@...gutronix.de, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/urgent] sched_clock: Disable seqlock lockdep usage
 in sched_clock()

On 01/12/2014 10:42 AM, tip-bot for John Stultz wrote:
> Commit-ID:  7a06c41cbec33c6dbe7eec575c61986122617408
> Gitweb:     http://git.kernel.org/tip/7a06c41cbec33c6dbe7eec575c61986122617408
> Author:     John Stultz <john.stultz@...aro.org>
> AuthorDate: Thu, 2 Jan 2014 15:11:14 -0800
> Committer:  Ingo Molnar <mingo@...nel.org>
> CommitDate: Sun, 12 Jan 2014 10:14:00 +0100
>
> sched_clock: Disable seqlock lockdep usage in sched_clock()
>
> Unfortunately the seqlock lockdep enablement can't be used
> in sched_clock(), since the lockdep infrastructure eventually
> calls into sched_clock(), which causes a deadlock.
>
> Thus, this patch changes all generic sched_clock() usage
> to use the raw_* methods.
>
> Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>
> Reported-by: Krzysztof Hałasa <khalasa@...p.pl>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> Cc: Willy Tarreau <w@....eu>
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Link: http://lkml.kernel.org/r/1388704274-5278-2-git-send-email-john.stultz@linaro.org
> Signed-off-by: Ingo Molnar <mingo@...nel.org>

Hey Ingo,
    Just wanted to follow up here, since I've still not seen this (and
the raw_ renaming patch) submitted to Linus. These address a lockup that
triggers on ARM systems if lockdep is enabled and it would be good to
get it in before 3.13 is out.

thanks
-john


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