lkml.org 
[lkml]   [2018]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [RFC] rcu: Prevent expedite reporting within RCU read-side section
From
Date
On 3/9/2018 5:41 PM, Byungchul Park wrote:
> On Thu, Mar 08, 2018 at 10:01:56AM -0800, Paul E. McKenney wrote:
>> On Thu, Mar 08, 2018 at 07:08:25PM +0900, Byungchul Park wrote:
>
> [...]
>
>>> 2. Clear its bit of ->expmask *only* when it's out of RCU read
>>> sections and keep others unchanged. So it will be cleared at the
>>> end of the RCU read section in that case.
>>>
>>> This option would also work because we anyway check both
>>> ->exp_tasks and ->expmask to finish the expedite-gp.
>>
>> This could be made to work, but one shortcoming is that the grace
>> period would end up waiting on later read-side critical sections
>> that it does not really need to wait on. Also, eventually all the
>
> I don't think it waits on any later ones since ->expmask would be
> cleared at the end of the previous RCU read section.

Now having simplified my patch, with the simplified version, I can
see what you were saying. Right, the expedite-gp might be extended
as you said. That optimization cannot be achieved this way without
reggression.

You're awesome. Thank you for explaning the reason why not.

--
Thanks,
Byungchul

\
 
 \ /
  Last update: 2018-03-09 09:54    [W:0.045 / U:2.872 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site