Messages in this thread | | | From | Philippe Rétornaz <> | Subject | Re: ftrace performance impact with different configuration | Date | Sat, 31 Dec 2011 00:31:55 +0100 |
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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
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