Re: [RFC] locking/rwsem: Avoid issuing wakeup before setting the reader waiter to nil

From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Yongji Xie <elohimes@gmail.com>,
	dave@stgolabs.net, mingo@redhat.com, will.deacon@arm.com,
	linux-kernel@vger.kernel.org, Xie Yongji <xieyongji@baidu.com>,
	zhangyu31@baidu.com, liuqi16@baidu.com, yuanlinsi01@baidu.com,
	nixun@baidu.com, lilin24@baidu.com,
	andrea.parri@amarulasolutions.com
Subject: Re: [RFC] locking/rwsem: Avoid issuing wakeup before setting the reader waiter to nil
Date: Mon, 7 Jan 2019 10:35:31 -0500	[thread overview]
Message-ID: <904530fd-10b6-208c-4baf-faf382f74a7f@redhat.com> (raw)
In-Reply-To: <20190107153125.GL2218@hirez.programming.kicks-ass.net>

On 01/07/2019 10:31 AM, Peter Zijlstra wrote:
> On Mon, Jan 07, 2019 at 09:35:09AM -0500, Waiman Long wrote:
>> On 12/17/2018 08:12 AM, Yongji Xie wrote:
>>> On Mon, 17 Dec 2018 at 19:37, Peter Zijlstra <peterz@infradead.org> wrote:
>>>> On Mon, Dec 10, 2018 at 11:12:52PM +0800, Yongji Xie wrote:
>>>>> Hi Peter,
>>>>>
>>>>> Please let me know If there is any progress on this issue. Thank you!
>>>> Right, sorry, my brain was filled with snot and didn't want to make
>>>> sense of things.
>>>>
>>>> I've put some patches here:
>>>>
>>>>   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core
>>>>
>>>> Could you have a look?
>>> That looks good to me. Thank you!
>>>
>>> Thanks,
>>> Yongji
>> Peter,
>>
>> Are you planning to move the patch over to tip as the merge window has
>> just closed?
> Sorry; yes, probably, I just got back from a 2 week holiday and am
> somewhat scrambling to remember where I left off and what all landed in
> my inbox.

Happy New Year!

I have bug reports on some mysterious rwsem related hangs which I think
can probably be fixed by this patch. That is why I am looking forward
for it to land into the tip tree.

Thanks,
Longman