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From: Bart Van Assche <bvanassche@acm.org>
To: dgilbert@interlog.com, Christoph Hellwig <hch@infradead.org>
Cc: SCSI development list <linux-scsi@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	James Bottomley <james.bottomley@hansenpartnership.com>,
	Milan Broz <gmazyland@gmail.com>
Subject: Re: [PATCH] scsi_debug: deadlock between completions and surprise module removal
Date: Mon, 08 Sep 2014 11:11:23 +0200	[thread overview]
Message-ID: <540D72BB.2020100@acm.org> (raw)
In-Reply-To: <540B1CC6.8010800@interlog.com>

On 09/06/14 16:40, Douglas Gilbert wrote:
> On 14-09-05 11:25 AM, Bart Van Assche wrote:
>> An LLD must call scsi_remove_host() directly or indirectly from the
>> module
>> cleanup path. scsi_remove_host() triggers a call to
>> blk_cleanup_queue(). That
>> last function sets the flag QUEUE_FLAG_DYING which prevents that new
>> I/O is
>> queued and waits until previously queued requests have finished before
>> returning.
>
> And they do call scsi_remove_host(). But they do that toward
> the end of their clean-up. The problem that I observed has
> already happened before that.
>
> IOW I think the QUEUE_FLAG_DYING state needs to be set and
> acknowledged as the first order of business by the code
> that implements 'rmmod LLD'.

Hello Doug,

In the scsi_debug driver scsi_remove_host() is called from inside the 
sdebug_driver_remove() callback function. Unless I have missed something 
it is not guaranteed that that callback function is invoked before 
unloading of the scsi_debug driver has finished. I think most of the 
code in sdebug_driver_remove() should be moved to sdebug_remove_adapter().

Bart.


  parent reply	other threads:[~2014-09-08  9:11 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-31 23:09 [PATCH] scsi_debug: deadlock between completions and surprise module removal Douglas Gilbert
2014-09-01 15:36 ` Christoph Hellwig
2014-09-01 19:52   ` Douglas Gilbert
2014-09-05  5:24 ` Christoph Hellwig
2014-09-05 13:56   ` Douglas Gilbert
2014-09-05 15:25     ` Bart Van Assche
2014-09-06 14:40       ` Douglas Gilbert
2014-09-06 14:44         ` Christoph Hellwig
2014-09-08  9:11         ` Bart Van Assche [this message]
2014-09-08 15:07           ` Christoph Hellwig
2014-09-08 20:31             ` Douglas Gilbert
2014-09-09 15:30               ` Christoph Hellwig
2014-09-25 12:13 ` Christoph Hellwig
2014-10-03 18:16   ` Elliott, Robert (Server Storage)

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