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

From:  Linus Torvalds <torvalds-AT-linux-foundation.org>
To:  Chris Mason <chris.mason-AT-oracle.com>
Subject:  Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning
Date:  Thu, 8 Jan 2009 10:00:57 -0800 (PST)
Message-ID:  <alpine.LFD.2.00.0901080955400.3283@localhost.localdomain>
Cc:  Peter Zijlstra <peterz-AT-infradead.org>, Ingo Molnar <mingo-AT-elte.hu>, Steven Rostedt <rostedt-AT-goodmis.org>, paulmck-AT-linux.vnet.ibm.com, Gregory Haskins <ghaskins-AT-novell.com>, Matthew Wilcox <matthew-AT-wil.cx>, Andi Kleen <andi-AT-firstfloor.org>, Andrew Morton <akpm-AT-linux-foundation.org>, Linux Kernel Mailing List <linux-kernel-AT-vger.kernel.org>, linux-fsdevel <linux-fsdevel-AT-vger.kernel.org>, linux-btrfs <linux-btrfs-AT-vger.kernel.org>, Thomas Gleixner <tglx-AT-linutronix.de>, Nick Piggin <npiggin-AT-suse.de>, Peter Morreale <pmorreale-AT-novell.com>, Sven Dietrich <SDietrich-AT-novell.com>
Archive-link:  Article



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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