linux-kernel - Re: [tip:core/locking] x86/smp: Move waiting on contended ticket lock out of line

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Message-ID: <511C35CB.2010103@zytor.com>
Date:	Wed, 13 Feb 2013 16:54:35 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Rik van Riel <riel@...hat.com>, rostedt@...dmiss.org,
	aquini@...hat.com, Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michel Lespinasse <walken@...gle.com>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:core/locking] x86/smp: Move waiting on contended ticket
 lock out of line

On 02/13/2013 10:30 AM, Linus Torvalds wrote:
> 
> Sadly, gcc doesn't seem to allow specifying which registers are
> clobbered any easy way, which means that both the caller and the
> callee *both* tend to need to have some asm interface. So we bothered
> to do this for __read_lock_failed, but we have *not* bothered to do
> the same for the otherwise very similar __mutex_fastpath_lock() case,
> for example.
> 

It does for the callee, but only on a whole-file basis.  It would be a
lot nicer if we could do it with function attributes.

	-hpa


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