Message-ID: <4D9E579C.3030101@intel.com>
Date: Fri, 08 Apr 2011 08:32:28 +0800
From: Huang Ying <ying.huang@intel.com>
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To: Russell King - ARM Linux <linux@arm.linux.org.uk>
CC: Len Brown <lenb@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, "Luck, Tony" <tony.luck@intel.com>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        Richard Henderson <rth@twiddle.net>, Mikael Starvik <starvik@axis.com>,
        David Howells <dhowells@redhat.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Hirokazu Takata <takata@linux-m32r.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Michal Simek <monstr@monstr.eu>, Ralf Baechle <ralf@linux-mips.org>,
        Kyle McMartin <kyle@mcmartin.ca>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Chen Liqin <liqin.chen@sunplusct.com>,
        "David S. Miller" <davem@davemloft.net>,
        Ingo Molnar <mingo@redhat.com>, Chris Zankel <chris@zankel.net>
Subject: Re: [PATCH -v2 1/4] Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG
References: <1302139746-1030-1-git-send-email-ying.huang@intel.com> <1302139746-1030-2-git-send-email-ying.huang@intel.com> <20110407173953.GB17049@n2100.arm.linux.org.uk>
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On 04/08/2011 01:39 AM, Russell King - ARM Linux wrote:
> 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.

OK.  Will do this.

Best Regards,
Huang Ying
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