linux-kernel - Re: [PATCH -v2 1/4] Add Kconfig option ARCH_HAVE_NMI_SAFE

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Message-ID: <20110407173953.GB17049@n2100.arm.linux.org.uk>
Date:	Thu, 7 Apr 2011 18:39:53 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>,
	Tony Luck <tony.luck@...el.com>, linux-acpi@...r.kernel.org,
	Richard Henderson <rth@...ddle.net>,
	Mikael Starvik <starvik@...s.com>,
	David Howells <dhowells@...hat.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Hirokazu Takata <takata@...ux-m32r.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Michal Simek <monstr@...str.eu>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Kyle McMartin <kyle@...artin.ca>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Chen Liqin <liqin.chen@...plusct.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...hat.com>, Chris Zankel <chris@...kel.net>
Subject: Re: [PATCH -v2 1/4] Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG

On Thu, Apr 07, 2011 at 09:29:03AM +0800, Huang Ying wrote:
> cmpxchg() is widely used by lockless code, including NMI-safe lockless
> code.  But on some architectures, the cmpxchg() implementation is not
> NMI-safe, on these architectures the lockless code may need to a
> spin_trylock_irqsave() based implementation.
> 
> This patch adds a Kconfig option: ARCH_HAVE_NMI_SAFE_CMPXCHG, so that
> NMI-safe lockless code can depend on it or provide different
> implementation according to it.
> 
> On many architectures, cmpxchg is only NMI-safe for several specific
> operand sizes. So, ARCH_HAVE_NMI_SAFE_CMPXCHG define in this patch
> only guarantees cmpxchg is NMI-safe for sizeof(unsigned long).

As this no longer touches any ARM code, I thinky you can drop me from the
CC list.  Thanks.
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