From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] scsi_debug: deadlock between completions and surprise
 module removal
Date: Sat, 6 Sep 2014 07:44:06 -0700
Message-ID: <20140906144406.GA25469@infradead.org>
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 <20140905052402.GA27094@infradead.org>
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 <5409D5D0.8060801@acm.org>
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To: Douglas Gilbert <dgilbert@interlog.com>
Cc: Bart Van Assche <bvanassche@acm.org>, Christoph Hellwig <hch@infradead.org>, 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>

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.