linux-kernel - Re: [PATCH] scsi_debug: deadlock between completions and surprise module removal

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Date:	Sat, 6 Sep 2014 07:44:06 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Douglas Gilbert <dgilbert@...erlog.com>
Cc:	Bart Van Assche <bvanassche@....org>,
	Christoph Hellwig <hch@...radead.org>,
	SCSI development list <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	James Bottomley <james.bottomley@...senpartnership.com>,
	Milan Broz <gmazyland@...il.com>
Subject: Re: [PATCH] scsi_debug: deadlock between completions and surprise
 module removal

On Sat, Sep 06, 2014 at 10:40:06AM -0400, Douglas Gilbert wrote:
> 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'.

That's how driver should implement their ->remove driver callback:

foo_remove()
{
	scsi_remove_host()
	< actual cleanup here>

	scsi_host_put();
}

if a driver doesn't do that, thats a bug in the driver which needs
fixing.
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