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

From: Waiman Long
Date: Mon Jan 07 2019 - 10:35:38 EST

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@xxxxxxxxxxxxx> 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:// 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.