From: Sasha Levin <sasha.levin@oracle.com>
To: John Stultz <john.stultz@linaro.org>,
LKML <linux-kernel@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Prarit Bhargava <prarit@redhat.com>,
Richard Cochran <richardcochran@gmail.com>,
Ingo Molnar <mingo@kernel.org>, stable <stable@vger.kernel.org>
Subject: Re: [RFC][PATCH 3/5] timekeeping: Avoid possible deadlock from clock_was_set_delayed
Date: Thu, 12 Dec 2013 11:34:58 -0500 [thread overview]
Message-ID: <52A9E5B2.8040702@oracle.com> (raw)
In-Reply-To: <1386789098-17391-4-git-send-email-john.stultz@linaro.org>
On 12/11/2013 02:11 PM, John Stultz wrote:
> As part of normal operaions, the hrtimer subsystem frequently calls
> into the timekeeping code, creating a locking order of
> hrtimer locks -> timekeeping locks
>
> clock_was_set_delayed() was suppoed to allow us to avoid deadlocks
> between the timekeeping the hrtimer subsystem, so that we could
> notify the hrtimer subsytem the time had changed while holding
> the timekeeping locks. This was done by scheduling delayed work
> that would run later once we were out of the timekeeing code.
>
> But unfortunately the lock chains are complex enoguh that in
> scheduling delayed work, we end up eventually trying to grab
> an hrtimer lock.
>
> Sasha Levin noticed this in testing when the new seqlock lockdep
> enablement triggered the following (somewhat abrieviated) message:
[snip]
This seems to work for me, I don't see the lockdep spew anymore.
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Thanks,
Sasha
next prev parent reply other threads:[~2013-12-12 16:34 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1386789098-17391-1-git-send-email-john.stultz@linaro.org>
2013-12-11 19:11 ` [RFC][PATCH 1/5] timekeeping: Fix lost updates to tai adjustment John Stultz
2013-12-11 19:11 ` [RFC][PATCH 2/5] timekeeping: Fix potential lost pv notification of time change John Stultz
2013-12-11 19:11 ` [RFC][PATCH 3/5] timekeeping: Avoid possible deadlock from clock_was_set_delayed John Stultz
2013-12-12 13:23 ` Ingo Molnar
2013-12-12 18:53 ` John Stultz
2013-12-12 16:34 ` Sasha Levin [this message]
2013-12-12 18:32 ` Sasha Levin
2013-12-12 18:59 ` John Stultz
2013-12-12 19:05 ` Sasha Levin
2013-12-12 19:13 ` John Stultz
2013-12-17 5:15 ` John Stultz
2013-12-17 6:41 ` Sasha Levin
2013-12-17 16:34 ` John Stultz
2013-12-11 19:11 ` [RFC][PATCH 4/5] timekeeping: Fix CLOCK_TAI timer/nanosleep delays John Stultz
2013-12-12 13:25 ` Ingo Molnar
2013-12-12 18:31 ` John Stultz
2013-12-13 14:10 ` Ingo Molnar
2013-12-11 19:11 ` [RFC][PATCH 5/5] timekeeping: Fix missing timekeeping_update in suspend path John Stultz
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=52A9E5B2.8040702@oracle.com \
--to=sasha.levin@oracle.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=prarit@redhat.com \
--cc=richardcochran@gmail.com \
--cc=stable@vger.kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).