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

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Message-ID: <20140115063827.GA11941@gmail.com>
Date:	Wed, 15 Jan 2014 07:38:27 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	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()


* John Stultz <john.stultz@...aro.org> wrote:

> 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.

It's in tip:core/urgent, i.e. lined up for v3.13, I plan to send it to 
Linus later today.

Thanks,

	Ingo
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