From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] libsas: Check for completed commands before calling
        lldd_abort_task()
Date: Mon, 8 Jan 2018 12:23:48 +0100
Message-ID: <20180108112348.GA7106@lst.de>
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To: Hannes Reinecke <hare@suse.de>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>, Christoph Hellwig <hch@lst.de>, James Bottomley <james.bottomley@hansenpartnership.com>, linux-scsi@vger.kernel.org, Yves-Alexis Perez <corsac@debian.org>, Hannes Reinecke <hare@suse.com>

On Mon, Jan 08, 2018 at 11:51:56AM +0100, Hannes Reinecke wrote:
> The abort handler might be racing with command completion, so the
> task might already be NULL by the time the abort handler is called.

But without taking dev_done_lock (or using cmpxchg) what prevents
use from still hitting this, although in a more narrow window?