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

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Message-ID: <4D775FA4.50706@monstr.eu>
Date:	Wed, 09 Mar 2011 12:08:20 +0100
From:	Michal Simek <monstr@...str.eu>
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>,
	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>,
	Chris Metcalf <cmetcalf@...era.com>,
	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

Michel Lespinasse wrote:
> Aplogies for the long CC list - as this proposal involves asm changes
> in many architectures, and I have only been able to test on x86,
> I have tried to include one maintainer from every arch so they can
> hopefully double check me. I do think I got all architectures right,
> but you can never be 100% sure...
> 
> ------------------------------------8<---------------------------------
> 
> 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.
> 
> Signed-off-by: Michel Lespinasse <walken@...gle.com>
> ---
>  arch/alpha/include/asm/futex.h      |   22 +++++++++-------
>  arch/arm/include/asm/futex.h        |   23 +++++++++--------
>  arch/frv/include/asm/futex.h        |    3 +-
>  arch/ia64/include/asm/futex.h       |    9 ++++--
>  arch/microblaze/include/asm/futex.h |   24 ++++++++++--------

For microblaze:
Tested-by: Michal Simek <monstr@...str.eu>

M

-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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