Message-ID: <52E155A8.7000206@hp.com>
Date: Thu, 23 Jan 2014 12:47:20 -0500
From: Waiman Long <waiman.long@hp.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12
MIME-Version: 1.0
To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Peter Zijlstra <peterz@infradead.org>,
        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" <linux-arch@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Linux Kernel Mailing List <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>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        George Spelvin <linux@horizon.com>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        Scott J Norton <scott.norton@hp.com>
Subject: Re: [PATCH v10 1/4] qrwlock: A queue read/write lock implementation
References: <1390426438-31252-1-git-send-email-Waiman.Long@hp.com> <1390426438-31252-2-git-send-email-Waiman.Long@hp.com> <20140123100751.GS30183@twins.programming.kicks-ass.net> <52E14D67.4000202@hp.com> <CA+55aFzhx6K9A62ve6E5X4juvNPewED_g1nWwq+-EY0fd0A-0g@mail.gmail.com>
In-Reply-To: <CA+55aFzhx6K9A62ve6E5X4juvNPewED_g1nWwq+-EY0fd0A-0g@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org

On 01/23/2014 12:15 PM, Linus Torvalds wrote:
> On Thu, Jan 23, 2014 at 9:12 AM, Waiman Long<waiman.long@hp.com>  wrote:
>> I thought that all atomic RMW instructions are memory barrier.
> On x86 they are. Not necessarily elsewhere.
>
>> If they are not, what kind of barrier should be added?
> smp_mb__before_atomic_xyz() and smp_mb__after_atomic_xyz() will do it,
> and are no-op (well, barriers - I don't think it matters) on x86.
>
>              Linus
> -

Thank for the info. I am less familiar with that kind of issues on other 
architecture. I will add a smp_mb__after_atomic_dec() & send out a new 
patch.

-Longman
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/