linux-kernel - Re: [PATCH 10/19] Add Kconfig option ARCH_HAVE_NMI_SAFE

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Date:	Wed, 03 Aug 2011 09:44:30 +0100
From:	David Howells <dhowells@...hat.com>
To:	Len Brown <lenb@...nel.org>
Cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, Huang Ying <ying.huang@...el.com>,
	Richard Henderson <rth@...ddle.net>,
	Mikael Starvik <starvik@...s.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Tony Luck <tony.luck@...el.com>,
	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>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH 10/19] Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG

Len Brown <lenb@...nel.org> wrote:

> From: Huang Ying <ying.huang@...el.com>
> 
> 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 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).
> 
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> Acked-by: Mike Frysinger <vapier@...too.org>
> Acked-by: Paul Mundt <lethal@...ux-sh.org>
> Acked-by: Hans-Christian Egtvedt <hans-christian.egtvedt@...el.com>
> Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Acked-by: Chris Metcalf <cmetcalf@...era.com>
> CC: Richard Henderson <rth@...ddle.net>
> CC: Mikael Starvik <starvik@...s.com>
> CC: David Howells <dhowells@...hat.com>
> CC: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> CC: Tony Luck <tony.luck@...el.com>
> CC: Hirokazu Takata <takata@...ux-m32r.org>
> CC: Geert Uytterhoeven <geert@...ux-m68k.org>
> CC: Michal Simek <monstr@...str.eu>
> CC: Ralf Baechle <ralf@...ux-mips.org>
> CC: Kyle McMartin <kyle@...artin.ca>
> CC: Martin Schwidefsky <schwidefsky@...ibm.com>
> CC: Chen Liqin <liqin.chen@...plusct.com>
> CC: "David S. Miller" <davem@...emloft.net>
> CC: Ingo Molnar <mingo@...hat.com>
> CC: Chris Zankel <chris@...kel.net>
> Signed-off-by: Len Brown <len.brown@...el.com>

Acked-by: David Howells <dhowells@...hat.com> [FRV]
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