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

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Message-ID: <alpine.LFD.2.00.0901080955400.3283@localhost.localdomain>
Date:	Thu, 8 Jan 2009 10:00:57 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chris Mason <chris.mason@...cle.com>
cc:	Peter Zijlstra <peterz@...radead.org>, 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>,
	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



Unrelated:

On Thu, 8 Jan 2009, Chris Mason wrote:
>
> RIP: 0010:[<ffffffff8024f4de>]  [<ffffffff8024f4de>] __cmpxchg+0x36/0x3f

Ouch. HOW THE HELL DID THAT NOT GET INLINED?

cmpxchg() is a _single_ instruction if it's inlined, but it's a horrible 
mess of dynamic conditionals on the (constant - per call-site) size 
argument if it isn't.

It looks like you probably enabled the "let gcc mess up inlining" config 
option.

Ingo - I think we need to remove that crap again. Because gcc gets the 
inlining horribly horribly wrong. As usual.

				Linus
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