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Date: Thu, 1 Mar 2007 16:27:16 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Chuck Ebbert <cebbert@...hat.com> Cc: tglx@...utronix.de, Ingo Molnar <mingo@...e.hu>, john stultz <johnstul@...ibm.com>, Roman Zippel <zippel@...ux-m68k.org>, Mike Galbraith <efault@....de>, Ken Chen <kenneth.w.chen@...el.com>, balducci@...ts.it, LKML <linux-kernel@...r.kernel.org>, Greg KH <greg@...ah.com> Subject: Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value On Thu, 01 Mar 2007 18:45:14 -0500 Chuck Ebbert <cebbert@...hat.com> wrote: > Thomas Gleixner wrote: > > Problem description at: > > http://bugzilla.kernel.org/show_bug.cgi?id=8048 > > > > Commit b18ec80396834497933d77b81ec0918519f4e2a7 > > [PATCH] sched: improve migration accuracy > > optimized the scheduler time calculations, but broke posix-cpu-timers. > > > > The problem is that the p->last_ran value is not updated after a context > > switch. So a subsequent call to current_sched_time() calculates with a > > stale p->last_ran value, i.e. accounts the full time, which the task was > > scheduled away. > > > > Signed-off-by: Thomas Gleixner <tglx@...utronix.de> > > > > Index: linux-2.6/kernel/sched.c > > =================================================================== > > --- linux-2.6.orig/kernel/sched.c > > +++ linux-2.6/kernel/sched.c > > @@ -3566,7 +3566,7 @@ switch_tasks: > > > > sched_info_switch(prev, next); > > if (likely(prev != next)) { > > - next->timestamp = now; > > + next->timestamp = next->last_ran = now; > > rq->nr_switches++; > > rq->curr = next; > > ++*switch_count; > > > > Is this going to be merged or not?? It just hit mainline. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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