lkml.org 
[lkml]   [2011]   [Dec]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: ftrace performance impact with different configuration
Date
Le vendredi 30 décembre 2011 17:25:41 Steven Rostedt a écrit :
> On Fri, 2011-12-30 at 14:07 +0100, Philippe Rétornaz wrote:
> > Sorry about being a bit naive, but why it is not possible to do it in
> > two
> > steps ?
> > call stop_machine to put the jmp which skip the call to mcount
> > Then wait until all tasks hits schedule() (synchronize_sched() ?)
> (...)
> There's no way to safely modify two instructions that depend on each
> other in a preemptible kernel, with the exception of waiting for all
> CPUs to hit idle (which may never happen on a busy system). And even
> that may be racy.
>

Thanks for the detailed explanation, I got it now. I guess the only way would
be to use the freezer api like freeze_processes() is doing. Looks like it does
not worth the pain.

Thanks !

Philippe

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-12-31 00:35    [W:7.331 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site