From: torvalds@linux-foundation.org (Linus Torvalds)
To: linux-arm-kernel@lists.infradead.org
Subject: v3.13-rc6+ regression (ARM board)
Date: Thu, 2 Jan 2014 12:43:52 -0800 [thread overview]
Message-ID: <CA+55aFz2dKw5HXy7DV1Aymoscg0MW7Zz28apan8dugUeqTd1QA@mail.gmail.com> (raw)
In-Reply-To: <52C5CC54.4050602@linaro.org>
On Thu, Jan 2, 2014 at 12:30 PM, John Stultz <john.stultz@linaro.org> wrote:
>
> So something else may be at play. Even with Linus' patch I reproduced a
> similar hang here.
>
> Still chasing it down, but it looks like a seqlock deadlock where we're
> calling read while holding the lock.
Hmm. Only with lockdep, right?
Does lockdep perhaps read the scheduler clock? Afaik, we have
lockstat_clock(), which uses local_clock(), which in turn translates
to sched_clock_cpu(smp_processor_id())..
So if that code now tries to read the scheduler clock when
update_sched_clock() is doing a update and has done a
write_seqcount_begin()...
Linus
next prev parent reply other threads:[~2014-01-02 20:43 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-31 10:37 v3.13-rc6+ regression (ARM board) Krzysztof Hałasa
2013-12-31 10:45 ` Willy Tarreau
2014-01-02 10:02 ` Krzysztof Hałasa
2014-01-02 10:14 ` Uwe Kleine-König
2014-01-02 12:07 ` Krzysztof Hałasa
2014-01-02 19:38 ` Linus Torvalds
2014-01-02 20:03 ` John Stultz
2014-01-02 20:30 ` John Stultz
2014-01-02 20:42 ` Stephen Boyd
2014-01-02 20:52 ` John Stultz
2014-01-02 20:43 ` Linus Torvalds [this message]
2014-01-02 21:34 ` John Stultz
2014-01-02 21:54 ` [PATCH] sched_clock: Disable seqlock lockdep usage in sched_clock John Stultz
2014-01-02 22:15 ` Linus Torvalds
2014-01-02 22:21 ` John Stultz
2014-01-02 23:11 ` [PATCH 1/2] seqlock: Use raw_ prefix instead of _no_lockdep John Stultz
2014-01-02 23:11 ` [PATCH 2/2] sched_clock: Disable seqlock lockdep usage in sched_clock John Stultz
2014-01-03 0:46 ` Stephen Boyd
2014-01-03 6:05 ` Krzysztof Hałasa
2014-01-03 0:46 ` [PATCH 1/2] seqlock: Use raw_ prefix instead of _no_lockdep Stephen Boyd
2014-01-03 0:50 ` Linus Torvalds
2014-01-04 0:28 ` John Stultz
2014-01-06 10:10 ` Peter Zijlstra
2014-01-03 6:01 ` v3.13-rc6+ regression (ARM board) Krzysztof Hałasa
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