Date: Wed, 7 Jan 2009 08:25:30 -0800 (PST)
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
cc: paulmck@linux.vnet.ibm.com, Gregory Haskins <ghaskins@novell.com>,
       Ingo Molnar <mingo@elte.hu>, Matthew Wilcox <matthew@wil.cx>,
       Andi Kleen <andi@firstfloor.org>, Chris Mason <chris.mason@oracle.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-fsdevel <linux-fsdevel@vger.kernel.org>,
       linux-btrfs <linux-btrfs@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Steven Rostedt <rostedt@goodmis.org>, Nick Piggin <npiggin@suse.de>,
       Peter Morreale <pmorreale@novell.com>,
       Sven Dietrich <SDietrich@novell.com>
Subject: Re: [PATCH -v4][RFC]: mutex: implement adaptive spinning
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On Wed, 7 Jan 2009, Peter Zijlstra wrote:
>
> Change mutex contention behaviour such that it will sometimes busy wait on
> acquisition - moving its behaviour closer to that of spinlocks.

Ok, this one looks _almost_ ok.

The only problem is that I think you've lost the UP case. 

In UP, you shouldn't have the code to spin, and the "spin_or_schedule()" 
should fall back to just the schedule case.

It migth also be worthwhile to try to not set the owner, and re-organize 
that a bit (by making it a inline function that sets the owner only for 
CONFIG_SMP or lockdep/debug). 

			Linus
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