Date: Tue, 28 Feb 2012 18:11:32 +0100
From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Jens Axboe <axboe@kernel.dk>,
        linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [SCSI] sr: fix multi-drive performance, remove BKL
 replacement
Message-ID: <20120228181132.13f1088c@stein>
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On Feb 28 James Bottomley wrote:
> On Tue, 2012-02-28 at 16:42 +0000, Arnd Bergmann wrote:
> > I took another look and I believe the cdi->use_count in
> > cdrom_open/cdrom_release still requires some protection that is
> > currently provided by sr_mutex.
> 
> So I think this is fine ... it's protected by the bdev->bd_mutex.
> 
> >  Some parts of cdrom_ioctl also
> > access this variable and things like cdi->options or cdi->keeplocked.
> 
> This would be problematic because we no longer lock the ioctl.
> 
> > I could imagine that you can get rid of the mutex if you turn those
> > into atomics and bitops, but there may be other parts of cdrom_device_info
> > that need locking. A safer option to solve the performance problems
> > could be to replace sr_mutex with a per-device mutex inside of
> > cdrom_device_info.
> 
> I'd say the latter.

Thanks Arnd and James, I will pursue this when I get the time.
-- 
Stefan Richter
-=====-===-- --=- ===--
http://arcgraph.de/sr/
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