linux-kernel - Re: [PATCH] futex: cmpxchg_futex_value

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Date:	Mon, 7 Mar 2011 09:25:34 -0500
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Michel Lespinasse <walken@...gle.com>
CC:	Darren Hart <dvhltc@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Matt Turner <mattst88@...il.com>,
	Russell King <linux@....linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	Michal Simek <monstr@...str.eu>,
	Ralf Baechle <ralf@...ux-mips.org>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] futex: cmpxchg_futex_value_locked API change

On 3/6/2011 9:11 PM, Michel Lespinasse wrote:
> The cmpxchg_futex_value_locked API was funny in that it returned either
> the original, user-exposed futex value OR an error code such as -EFAULT.
> This was confusing at best, and could be a source of livelocks in places
> that retry the cmpxchg_futex_value_locked after trying to fix the issue
> by running fault_in_user_writeable().
>
> This change makes the cmpxchg_futex_value_locked API more similar to the
> get_futex_value_locked one, returning an error code and updating the
> original value through a reference argument.
> [...]
> diff --git a/arch/tile/include/asm/futex.h b/arch/tile/include/asm/futex.h

Makes sense to me; that API is a little crazy.

For the tile changes:

Acked-by: Chris Metcalf <cmetcalf@...era.com>

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

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