From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Richter Subject: Re: [PATCH] [SCSI] sr: fix multi-drive performance, remove BKL replacement Date: Tue, 28 Feb 2012 18:11:32 +0100 Message-ID: <20120228181132.13f1088c@stein> References: <20120228153244.70413d34@stein> <20120228170930.132f7c1e@stein> <1330445795.2822.134.camel@dabdike.int.hansenpartnership.com> <201202281642.16496.arnd@arndb.de> <1330448257.2822.138.camel@dabdike.int.hansenpartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1330448257.2822.138.camel@dabdike.int.hansenpartnership.com> Sender: linux-kernel-owner@vger.kernel.org To: James Bottomley Cc: Arnd Bergmann , Jens Axboe , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-scsi@vger.kernel.org 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/