Message-ID: <52692AE7.3060701@hp.com>
Date: Thu, 24 Oct 2013 10:12:55 -0400
From: Waiman Long <waiman.long@hp.com>
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To: Thomas Gleixner <tglx@linutronix.de>
CC: walken@google.com, 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, Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        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>,
        "Chandramouleeswaran, Aswin" <aswin@hp.com>,
        "Norton, Scott J" <scott.norton@hp.com>
Subject: Re: [PATCH v4 1/3] qrwlock: A queue read/write lock implementation
References: <1380722946-30468-1-git-send-email-Waiman.Long@hp.com> <1380722946-30468-2-git-send-email-Waiman.Long@hp.com> <20131023120004.GD2862@localhost> <52680022.1020200@hp.com> <alpine.DEB.2.02.1310241207500.4983@ionos.tec.linutronix.de>
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On 10/24/2013 06:14 AM, Thomas Gleixner wrote:
> On Wed, 23 Oct 2013, Waiman Long wrote:
>> On 10/23/2013 08:00 AM, walken@google.com wrote:
>>>> +	/*
>>>> +	 * Wait until the next one in queue set up the next field
>>>> +	 */
>>>> +	while (likely(!(next = ACCESS_ONCE(node->next))))
>>>> +		cpu_relax();
>>>> +	/*
>>>> +	 * The next one in queue is now at the head
>>>> +	 */
>>>> +notify_next:
>>>> +	barrier();
>>>> +	ACCESS_ONCE(next->wait) = false;
>>>> +	smp_wmb();
>>>> +}
>>> I believe this could be unified with mspin_lock() / mspin_unlock() in
>>> kernel/mutex.c ? (there is already talk of extending these functions
>>> to be used by rwsem for adaptive spinning as well...)
>> It probably can, but the unification can wait until the code are in.
> The unification has to be done as a part of this series. Cleanups are
> part of the development process of new code and not an optional
> feature.
>
> Thanks,
>
> 	tglx
>

There is an outstanding rwsem patch series that is doing the 
unification. I am waiting for that patch series to be at least in a tip 
or linux-next branch before doing the unification. Otherwise, it will 
cause merge conflict.

-Longman
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