linux-kernel - Re: [2.6.36-rc3] Workqueues, XFS, dependencies and deadlocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4C862F8E.7030507@kernel.org>
Date:	Tue, 07 Sep 2010 14:26:54 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Dave Chinner <david@...morbit.com>
CC:	linux-kernel@...r.kernel.org, xfs@....sgi.com,
	linux-fsdevel@...r.kernel.org
Subject: Re: [2.6.36-rc3] Workqueues, XFS, dependencies and deadlocks

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/