lkml.org 
[lkml]   [2008]   [Apr]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH]: Fix SMP-reordering race in mark_buffer_dirty


On Wed, 2 Apr 2008, Andrew Morton wrote:
>
> But then the test-and-set of an already-set flag would newly cause the
> cacheline to be dirtied, requiring additional bus usage to write it back?
>
> The CPU's test-and-set-bit operation could of course optimise that away in
> this case. But does it?

No, afaik no current x86 uarch will optimize away the write on a locked
instuction if it turns out to be unnecessary.

Can somebody find a timing reason to have the ugly code?

Linus


\
 
 \ /
  Last update: 2008-04-03 00:11    [W:0.494 / U:0.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site