Messages in this thread | | | Date | Thu, 21 Oct 2010 09:50:41 -0400 | From | Jason Baron <> | Subject | Re: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c |
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On Thu, Oct 21, 2010 at 01:03:28PM +0200, Peter Zijlstra wrote: > On Thu, 2010-10-21 at 07:01 -0400, Steven Rostedt wrote: > > On Thu, 2010-10-21 at 09:22 +0200, Peter Zijlstra wrote: > > > On Thu, 2010-10-21 at 11:58 +0900, Masami Hiramatsu wrote: > > > > > > > It seems there can be a bug in stop_machine() routine under > > > > heavy use. usually that is called just once at a time, but jump > > > > label and optprobe might call it heavily (thousands times?). > > > > So some racy situation can be happen easily. > > > > > > There are people doing hotplug stress testing, that too results in heavy > > > stop_machine usage. > > > > But with hotplug, isn't there a bit more time between stop machine > > calls? That is, you need to do a bit of work to bring down or up a CPU, > > and that will slow down the number of stop machine calls together. > > > > Here, we do a simple change and call stop machine() several times. > > > > Although, I agree, I do not think the bug is in stop machine itself, but > > perhaps the way we are using it might have some niche anomaly that we > > are hitting. > > Possibly, but wouldn't it make sense to batch up the work and simply > call stop_machine only once? I mean, if you already know you're going to > do this... >
it would. I know Masami is working on text_poke_smp_batch(), and I was planning to move to it when it was ready...nonetheless there is still a bug here...
thanks,
-Jason
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