lkml.org 
[lkml]   [2018]   [Dec]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 1/1] epoll: use rwlock in order to reduce ep_poll_callback() contention
On 2018-12-05 00:59, Andrea Parri wrote:
> Hi Roman,
>
> On Tue, Dec 04, 2018 at 12:50:58PM +0100, Roman Penyaev wrote:
>> On 2018-12-03 18:34, Linus Torvalds wrote:
>
>> > This also ends up making the memory ordering of "xchg()" very very
>> > important. Yes, we've documented it as being an ordering op, but I'm
>> > not sure we've relied on it this directly before.
>>
>> Seems exit_mm() does exactly the same, the following chunk:
>>
>> up_read(&mm->mmap_sem);
>>
>> self.task = current;
>> self.next = xchg(&core_state->dumper.next, &self);
>>
>>
>> At least code pattern looks similar.
>
> Maybe add a comment on top of (your) xchg() to note/justify these
> memory
> ordering requirements? As Paul said: "if there are races, this would
> help force them to happen" (and simplify the review, this/future).

Hi Andrea,

Sure, this path is tricky, so will I cook something up.

--
Roman

\
 
 \ /
  Last update: 2018-12-05 12:27    [W:0.035 / U:1.824 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site