linux-kernel - Re: [PATCH v2 2/3] mutex: add support for reservation style locks, v2

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Date:	Wed, 10 Apr 2013 11:33:22 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Daniel Vetter <daniel@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	linux-arch@...r.kernel.org, daniel.vetter@...ll.ch, x86@...nel.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, robclark@...il.com,
	tglx@...utronix.de, mingo@...e.hu, linux-media@...r.kernel.org
Subject: Re: [PATCH v2 2/3] mutex: add support for reservation style locks, v2

On Tue, Apr 09, 2013 at 06:28:08PM -0400, Steven Rostedt wrote:
> On Thu, Apr 04, 2013 at 06:41:02PM +0200, Peter Zijlstra wrote:
> > On Thu, 2013-04-04 at 15:31 +0200, Daniel Vetter wrote:
> > > The thing is now that you're not expected to hold these locks for a
> > > long
> > > time - if you need to synchronously stall while holding a lock
> > > performance
> > > will go down the gutters anyway. And since most current
> > > gpus/co-processors
> > > still can't really preempt fairness isn't that high a priority,
> > > either.
> > > So we didn't think too much about that.
> > 
> > Yeah but you're proposing a new synchronization primitive for the core
> > kernel.. all such 'fun' details need to be considered, not only those
> > few that bear on the one usecase.
> 
> Which bares the question, what other use cases are there?

Tbh I don't see any other either - but I agree with Peter and thinking
things through and making the api a bit more generic seems to help in
clarifying the semantics. Reminds me that I still need to draw a few
diagrams ;-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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