From: Tejun Heo <tj@kernel.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>,
linux-kernel@vger.kernel.org, Jens Axboe <jaxboe@fusionio.com>
Subject: Re: Strange block/scsi/workqueue issue
Date: Tue, 12 Apr 2011 11:51:45 +0900 [thread overview]
Message-ID: <20110412025145.GJ9673@mtj.dyndns.org> (raw)
In-Reply-To: <1302569276.2558.9.camel@mulgrave.site>
Hello, James.
On Mon, Apr 11, 2011 at 07:47:56PM -0500, James Bottomley wrote:
> Actually, I don't think it's anything to do with the user process stuff.
> The problem seems to be that the block delay function ends up being the
> last user of the SCSI device, so it does the final put of the sdev when
> it's finished processing. This will trigger queue destruction
> (blk_cleanup_queue) and so on with your analysis.
Hmm... this I can understand.
> The problem seems to be that with the new workqueue changes, the queue
> itself may no longer be the last holder of a reference on the sdev
> because the queue destruction is in the sdev release function and a
> queue cannot now be destroyed from its own delayed work. This is a bit
> contrary to the principles SCSI was using, which was that we drive queue
> lifetime from the sdev, not vice versa.
But confused here. Why does it make any difference whether the
release operation is in the request_fn context or not? What makes
SCSI refcounting different from others?
Thanks.
--
tejun
next prev parent reply other threads:[~2011-04-12 2:51 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-11 14:56 Strange block/scsi/workqueue issue Steven Whitehouse
2011-04-11 17:18 ` Tejun Heo
2011-04-11 17:29 ` Jens Axboe
2011-04-11 17:52 ` Steven Whitehouse
2011-04-12 0:14 ` Tejun Heo
2011-04-12 8:49 ` Steven Whitehouse
2011-04-12 0:47 ` James Bottomley
2011-04-12 2:51 ` Tejun Heo [this message]
2011-04-12 4:49 ` James Bottomley
2011-04-12 5:02 ` James Bottomley
2011-04-12 8:42 ` Steven Whitehouse
2011-04-12 13:42 ` James Bottomley
2011-04-12 14:06 ` Steven Whitehouse
2011-04-12 15:14 ` James Bottomley
2011-04-12 16:04 ` Steven Whitehouse
2011-04-12 16:27 ` James Bottomley
2011-04-12 16:51 ` Steven Whitehouse
2011-04-12 17:41 ` James Bottomley
2011-04-12 18:33 ` Steven Whitehouse
2011-04-12 19:56 ` James Bottomley
2011-04-12 20:30 ` Steven Whitehouse
2011-04-12 20:43 ` James Bottomley
2011-04-13 5:18 ` Tejun Heo
2011-04-13 6:06 ` Tejun Heo
2011-04-13 9:20 ` Steven Whitehouse
2011-04-13 14:00 ` Steven Whitehouse
2011-04-13 17:01 ` James Bottomley
2011-04-13 19:35 ` Steven Whitehouse
2011-04-13 20:12 ` Jens Axboe
2011-04-13 20:17 ` James Bottomley
2011-04-22 18:01 ` Tejun Heo
2011-04-22 18:06 ` James Bottomley
2011-04-22 18:30 ` Tejun Heo
2011-05-31 6:05 ` Anton V. Boyarshinov
2011-04-22 18:03 ` Tejun Heo
2011-04-12 5:15 ` Tejun Heo
2011-04-12 15:15 ` James Bottomley
2011-04-13 5:11 ` Tejun Heo
2011-04-13 14:15 ` James Bottomley
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