From: Tejun Heo <tj@kernel.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
xfs@oss.sgi.com
Subject: Re: [2.6.36-rc3] Workqueues, XFS, dependencies and deadlocks
Date: Tue, 07 Sep 2010 14:26:54 +0200 [thread overview]
Message-ID: <4C862F8E.7030507@kernel.org> (raw)
In-Reply-To: <4C861582.6080102@kernel.org>
On 09/07/2010 12:35 PM, Tejun Heo wrote:
> Can you please help me a bit more? Are you saying the following?
>
> Work w0 starts execution on wq0. w0 tries locking but fails. Does
> delay(1) and requeues itself on wq0 hoping another work w1 would be
> queued on wq0 which will release the lock. The requeueing should make
> w0 queued and executed after w1, but instead w1 never gets executed
> while w0 hogs the CPU constantly by re-executing itself. Also, how
> does delay(1) help with chewing up CPU? Are you talking about
> avoiding constant lock/unlock ops starving other lockers? In such
> case, wouldn't cpu_relax() make more sense?
Ooh, almost forgot. There was nr_active underflow bug in workqueue
code which could lead to malfunctioning max_active regulation and
problems during queue freezing, so you could be hitting that too. I
sent out pull request some time ago but hasn't been pulled into
mainline yet. Can you please pull from the following branch and add
WQ_HIGHPRI as discussed before and see whether the problem is still
reproducible? And if the problem is reproducible, can you please
trigger sysrq thread dump and attach it?
git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-linus
Thanks.
--
tejun
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WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-kernel@vger.kernel.org, xfs@oss.sgi.com,
linux-fsdevel@vger.kernel.org
Subject: Re: [2.6.36-rc3] Workqueues, XFS, dependencies and deadlocks
Date: Tue, 07 Sep 2010 14:26:54 +0200 [thread overview]
Message-ID: <4C862F8E.7030507@kernel.org> (raw)
In-Reply-To: <4C861582.6080102@kernel.org>
On 09/07/2010 12:35 PM, Tejun Heo wrote:
> Can you please help me a bit more? Are you saying the following?
>
> Work w0 starts execution on wq0. w0 tries locking but fails. Does
> delay(1) and requeues itself on wq0 hoping another work w1 would be
> queued on wq0 which will release the lock. The requeueing should make
> w0 queued and executed after w1, but instead w1 never gets executed
> while w0 hogs the CPU constantly by re-executing itself. Also, how
> does delay(1) help with chewing up CPU? Are you talking about
> avoiding constant lock/unlock ops starving other lockers? In such
> case, wouldn't cpu_relax() make more sense?
Ooh, almost forgot. There was nr_active underflow bug in workqueue
code which could lead to malfunctioning max_active regulation and
problems during queue freezing, so you could be hitting that too. I
sent out pull request some time ago but hasn't been pulled into
mainline yet. Can you please pull from the following branch and add
WQ_HIGHPRI as discussed before and see whether the problem is still
reproducible? And if the problem is reproducible, can you please
trigger sysrq thread dump and attach it?
git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-linus
Thanks.
--
tejun
next prev parent reply other threads:[~2010-09-07 12:26 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-07 7:29 [2.6.36-rc3] Workqueues, XFS, dependencies and deadlocks Dave Chinner
2010-09-07 7:29 ` Dave Chinner
2010-09-07 9:04 ` Tejun Heo
2010-09-07 9:04 ` Tejun Heo
2010-09-07 10:01 ` Dave Chinner
2010-09-07 10:01 ` Dave Chinner
2010-09-07 10:35 ` Tejun Heo
2010-09-07 10:35 ` Tejun Heo
2010-09-07 12:26 ` Tejun Heo [this message]
2010-09-07 12:26 ` Tejun Heo
2010-09-07 13:02 ` Dave Chinner
2010-09-07 13:02 ` Dave Chinner
2010-09-08 8:22 ` Dave Chinner
2010-09-08 8:22 ` Dave Chinner
2010-09-08 8:51 ` Tejun Heo
2010-09-08 8:51 ` Tejun Heo
2010-09-08 10:05 ` Dave Chinner
2010-09-08 10:05 ` Dave Chinner
2010-09-08 10:05 ` Dave Chinner
2010-09-08 14:10 ` Tejun Heo
2010-09-08 14:10 ` Tejun Heo
2010-09-07 12:48 ` Dave Chinner
2010-09-07 12:48 ` Dave Chinner
2010-09-07 15:39 ` Tejun Heo
2010-09-07 15:39 ` Tejun Heo
2010-09-08 7:34 ` Dave Chinner
2010-09-08 7:34 ` Dave Chinner
2010-09-08 8:20 ` Tejun Heo
2010-09-08 8:20 ` Tejun Heo
2010-09-08 8:28 ` Dave Chinner
2010-09-08 8:28 ` Dave Chinner
2010-09-08 8:46 ` Tejun Heo
2010-09-08 8:46 ` Tejun Heo
2010-09-08 10:12 ` Dave Chinner
2010-09-08 10:12 ` Dave Chinner
2010-09-08 10:28 ` Tejun Heo
2010-09-08 10:28 ` Tejun Heo
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