linux-kernel - Re: [RFC PATCH] cifs: Fix possible deadlock with cifs and work queues

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Message-ID: <20140321081706.271e390c@gandalf.local.home>
Date:	Fri, 21 Mar 2014 08:17:06 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Pavel Shilovsky <piastry@...rsoft.ru>
Cc:	Jeff Layton <jlayton@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-cifs <linux-cifs@...r.kernel.org>,
	Steve French <sfrench@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Clark Williams <williams@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tejun Heo <tj@...nel.org>, uobergfe@...hat.com
Subject: Re: [RFC PATCH] cifs: Fix possible deadlock with cifs and work
 queues

On Fri, 21 Mar 2014 12:32:12 +0400
Pavel Shilovsky <piastry@...rsoft.ru> wrote:


> Read and write codepaths both obtain lock_sem for read and then wait
> for cifsiod_wq to complete and release lock_sem. They don't do any
> lock_sem operations inside their work task queued to cifsiod_wq. But
> oplock code can obtain/release lock_sem in its work task. So, that's
> why I agree with Jeff and suggest to move the oplock code to a
> different work queue (cifsioopd_wq?) but leave read and write
> codepaths use cifsiod_wq.

OK, how about I submit a second patch that moves the reader and writer
to its own "safe" workqueue?

-- Steve

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