Message-ID: <53078865.8060808@hp.com>
Date: Fri, 21 Feb 2014 12:09:57 -0500
From: Waiman Long <waiman.long@hp.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Arnd Bergmann <arnd@arndb.de>,
        linux-arch@vger.kernel.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Michel Lespinasse <walken@google.com>,
        Andi Kleen <andi@firstfloor.org>, Rik van Riel <riel@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        George Spelvin <linux@horizon.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Daniel J Blueman <daniel@numascale.com>,
        Alexander Fyodorov <halcy@yandex.ru>,
        Aswin Chandramouleeswaran <aswin@hp.com>,
        Scott J Norton <scott.norton@hp.com>,
        Thavatchai Makphaibulchoke <thavatchai.makpahibulchoke@hp.com>
Subject: Re: [PATCH v4 3/3] qspinlock, x86: Add x86 specific optimization
 for 2 contending tasks
References: <1392669684-4807-1-git-send-email-Waiman.Long@hp.com> <1392669684-4807-4-git-send-email-Waiman.Long@hp.com> <20140221121222.GQ9987@twins.programming.kicks-ass.net> <530787F3.6020400@hp.com>
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On 02/21/2014 12:08 PM, Waiman Long wrote:
> On 02/21/2014 07:12 AM, Peter Zijlstra wrote:
>>
>> Why is this x86 only code?
>
> The code is making use of the fact that byte write is atomic which is 
> true in x86 and probably in a few other architectures. I could pull 
> these codes into the generic qspinlock.c file and set a flag in the 
> asm header file to activate it if it is what you want.
>
> -Longman

BTW, I also assume that 8-bit and 16-bit cmpxchg() and xchg() are available.

-Longman
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