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From: Tejun Heo <tj@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Jens Axboe <axboe@kernel.dk>, "Rafael J. Wysocki" <rjw@sisk.pl>,
	Linux-pm mailing list <linux-pm@vger.kernel.org>,
	Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: Bug in disk event polling
Date: Fri, 10 Feb 2012 13:12:55 -0800	[thread overview]
Message-ID: <20120210211255.GK19392@google.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1202101557280.1281-100000@iolanthe.rowland.org>

Hello, Alan.

On Fri, Feb 10, 2012 at 04:03:51PM -0500, Alan Stern wrote:
> None of those resets above should have occurred.  They are the result
> of trying to recover from the failure of a TEST UNIT READY command.

Thanks for the log.  Yeah, I was just thinking about libata and
wondering why it would break that badly.

> > > I have verified that changing all occurrences of system_nrt_wq in 
> > > block/genhd.c to system_freezable_wq fixes the bug.  However this may 
> > > not be the way you want to solve it; you may prefer to have a freezable 
> > > non-reentrant work queue.
> > 
> > Please feel free to send out a patch to fix the issue. :)
> 
> Is there a real reason for using system_nrt_wq?  Are you okay with just
> switching over to system_freezable_wq?

I think it should be nrt.  It assumes that no one else is running it
concurrently; otherwise, multiple CPUs could jump into
disk->fops->check_events() concurrently which can be pretty ugly.

Thanks.

-- 
tejun

  reply	other threads:[~2012-02-10 21:13 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-10 20:31 Bug in disk event polling Alan Stern
2012-02-10 20:46 ` Tejun Heo
2012-02-10 21:03   ` Alan Stern
2012-02-10 21:12     ` Tejun Heo [this message]
2012-02-10 21:44       ` Alan Stern
2012-02-11  0:23         ` Tejun Heo
2012-02-12 17:48           ` Alan Stern
2012-02-12 21:26             ` Rafael J. Wysocki
2012-02-12 22:02               ` Alan Stern
2012-02-13 17:30             ` Tejun Heo

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