Re: [PATCH v4 1/3] qrwlock: A queue read/write lock implementation

[Waiman Long <waiman.long@hp.com>]

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