linux-kernel - Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning

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Message-ID: <alpine.LFD.2.00.0901080746290.3283@localhost.localdomain>
Date:	Thu, 8 Jan 2009 08:11:22 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	paulmck@...ux.vnet.ibm.com, Gregory Haskins <ghaskins@...ell.com>,
	Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>,
	Chris Mason <chris.mason@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>
Subject: Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning



On Thu, 8 Jan 2009, Peter Zijlstra wrote:
> 
> This was done because the interaction between trylock_slowpath and that
> -1000 state hurt my head.

Yeah, it was a stupid hacky thing to avoid the "list_empty()", but doing 
it explicitly is fine (we don't hold the lock, so the list isn't 
necessarily stable, but doing "list_empty()" is fine because we don't ever 
dereference the pointers, we just compare the pointers themselves).

I shouldn't have done that hacky thing, it wasn't worth it.

		Linus
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