From: Jens Axboe <jens.axboe@oracle.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Elias Oltmanns <eo@nebensachen.de>,
linux-scsi@vger.kernel.org, stable@kernel.org
Subject: Re: [PATCH] SCSI: Fix some locking issues
Date: Wed, 2 Jul 2008 20:45:27 +0200 [thread overview]
Message-ID: <20080702184526.GM20055@kernel.dk> (raw)
In-Reply-To: <1215010189.3330.17.camel@localhost.localdomain>
On Wed, Jul 02 2008, James Bottomley wrote:
> On Wed, 2008-07-02 at 13:50 +0200, Jens Axboe wrote:
> > On Wed, Jul 02 2008, Elias Oltmanns wrote:
> > > > The blk_plug_queue change looks reasonable ... however, blk_plug_queue
> > > > itself looks like it might not entirely need the queue lock ... I need
> > > > to investigate more closely.
> > >
> > > Well, I rather think it does. We have to serialise access to the
> > > unplug_timer and there is a call to __set_bit() which, as I understand,
> > > requires the calling function to ensure atomicity.
> >
> > Yep, blk_plug_device() needs to be called with the queue lock held.
>
> That's what the comment says ... but if you replaced the test_bit with
> an atomic operation then the rest of it does look to be in no need of
> serialisation ... unless there's something I missed?
Indeed, but then you would have to use atomic bitops everywhere and that
is the bit we moved away from.
--
Jens Axboe
next prev parent reply other threads:[~2008-07-02 18:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-06-29 11:38 [PATCH] SCSI: Fix some locking issues Elias Oltmanns
2008-07-01 21:37 ` Elias Oltmanns
2008-07-02 1:55 ` James Bottomley
2008-07-02 7:08 ` Elias Oltmanns
2008-07-02 11:50 ` Jens Axboe
2008-07-02 14:49 ` James Bottomley
2008-07-02 18:45 ` Jens Axboe [this message]
2008-07-02 20:18 ` James Bottomley
2008-07-03 7:53 ` Elias Oltmanns
2008-07-03 10:38 ` Elias Oltmanns
2008-07-03 11:24 ` Jens Axboe
2008-07-03 16:31 ` James Bottomley
2008-07-03 17:54 ` Jens Axboe
2008-07-03 19:47 ` Elias Oltmanns
2008-07-03 21:33 ` James Bottomley
2008-07-02 14:46 ` James Bottomley
2008-07-02 15:59 ` Elias Oltmanns
2008-07-02 16:23 ` Matthew Wilcox
2008-07-03 7:12 ` Elias Oltmanns
2008-07-03 15:22 ` James Bottomley
2008-07-03 19:39 ` Elias Oltmanns
2008-07-03 15:47 ` Matthew Wilcox
2008-07-02 16:32 ` James Bottomley
2008-07-03 7:25 ` Elias Oltmanns
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