Messages in this thread |  | | Date | Fri, 7 Jul 2017 10:11:20 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/cputime: Fix using smp_processor_id() in preemptible |
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On Thu, Jul 06, 2017 at 08:18:41PM -0700, Wanpeng Li wrote: > --- a/kernel/sched/cputime.c > +++ b/kernel/sched/cputime.c > @@ -683,7 +683,7 @@ static u64 vtime_delta(struct vtime *vtime) > { > unsigned long long clock; > > - clock = sched_clock_cpu(smp_processor_id()); > + clock = sched_clock(); > if (clock < vtime->starttime) > return 0; >
This is broken. sched_clock_cpu() and sched_clock() do not have the exact same value :-/
So this ends up doing:
vtime->starttime = sched_clock_cpu(cpu);
/* ... */
clock = sched_clock();
delta = clock - vtime->starttime;
And you compute a delta using two different clocks.
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