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Subject: Re: [PATCH][RESEND] scalable rw_mutex
From: Peter Zijlstra <peterz@infradead.org>
To: Ryan Hope <rmh3093@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>
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Date: Fri, 08 Aug 2008 16:15:23 +0200
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A: http://en.wikipedia.org/wiki/Top_post
Q: Were do I find info about this thing called top-posting?
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

On Fri, 2008-08-08 at 10:04 -0400, Ryan Hope wrote:
> Sorry for not CCing you, I had intended to CC you and others but I
> clicked send too quick. One of the reiser4 todo's was remove all
> semaphore's, I didnt realize rw_semaphores were not real semaphores

Yeah, more people make that mistake. They're basically a sleeping rw
lock and already conform to the semantics that are required for lockdep
and are thus also already covered by lockdep.

> On Fri, Aug 8, 2008 at 6:21 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Thu, 2008-08-07 at 18:56 -0400, Ryan Hope wrote:
> >> This was posted sometime last year I think and it never got merged. Can this get
> >> a go around in -mm, it would help in converting the semaphore's in reiser4 to
> >> mutexes.
> >
> > Thanks for CC'ing me :-/
> >
> > I dropped it because its only more scalable up to around 4 cpus.
> >
> > Also, how would it help reiser4? using rwsems is perfectly fine - as
> > they aren't actual semaphores.

<snip code>

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