Date: Sat, 5 Mar 2016 16:25:17 -0500
From: Wakko Warner <wakko@animx.eu.org>
To: Johan de Jong <jrdejong@gmail.com>
Cc: linux-kernel@vger.kernel.org, Thomas Schmitt <scdbackup@gmx.net>
Subject: Re: SCSI sr driver: parallel writes to optical serialized which
 hurts performance (sr_mutex)
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Johan de Jong wrote:
> In the mean time I have applied and tested the 2013 patch by Otto Meta:
> 
> http://marc.info/?l=linux-scsi&m=135705061804384&w=2
> 
> which, in short, replaces mutex_lock(&sr_mutex) (global mutex), that
> was introduced in 2010 to replace lock_kernel(), by per-device mutexes
> and allowing concurrent ioctl(SG_IO) in different processes with
> different sr devices.

There seems to be a few patches floating around.  I've had one running on
3.3.0 for a long time w/o any issues.  I'm currently using the one from Tim
Small (Search for subject Fix performance burning or extracting audio etc.
from multiple optical drives.) on 4.x (where x is 3-4) and a 3.14.something
without any issues.

I still have the emails from Tim.  My current usage is 2 systems with 3
burners from the same source.