lkml.org 
[lkml]   [2015]   [Feb]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] sched/completion: completion_done() should serialize with complete()
From
Date
On Thu, 2015-02-12 at 20:59 +0100, Oleg Nesterov wrote:
> Commit de30ec47302c "Remove unnecessary ->wait.lock serialization when
> reading completion state" was not correct, without lock/unlock the code
> like stop_machine_from_inactive_cpu()
>
> while (!completion_done())
> cpu_relax();
>
> can return before complete() finishes its spin_unlock() which writes to
> this memory. And spin_unlock_wait().

How about reverting the patch altogether?

This was never a problem nor have I ever seen a performance issues in
completions that would merit these lockless checks. The commit changelog
has *zero* information, so I don't know if this was ever a real issue.

Thanks,
Davidlohr



\
 
 \ /
  Last update: 2015-02-13 23:01    [W:0.128 / U:0.332 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site