Messages in this thread | | | Date | Wed, 4 May 2016 19:51:14 +0800 | Subject | Re: [lkp] [sched/fair] 41e0d37f7a: divide error: 0000 [#1] SMP | From | Wanpeng Li <> |
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2016-05-04 19:44 GMT+08:00 Rafael J. Wysocki <rafael@kernel.org>: > On Wed, May 4, 2016 at 2:58 AM, Wanpeng Li <kernellwp@gmail.com> wrote: >> 2016-05-03 20:15 GMT+08:00 Rafael J. Wysocki <rafael@kernel.org>: >>> On Tue, May 3, 2016 at 10:32 AM, Peter Zijlstra <peterz@infradead.org> wrote: >>>> On Tue, May 03, 2016 at 09:10:51AM +0800, kernel test robot wrote: >>>>> FYI, we noticed the following commit: >>>>> >>>>> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core >>>>> commit 41e0d37f7ac81297c07ba311e4ad39465b8c8295 ("sched/fair: Do not call cpufreq hook unless util changed") >>>> > > [cut] > >>>> >>>> That's intel_pstate.c:get_avg_frequency(), which assumes mperf != 0. It >>>> being 0 seems to suggest intel_pstate_sample() hasn't been called yet or >>>> so. >>> >>> Well, what's the tree based on? >>> >>> The mainline does this: >>> >>> bool sample_taken = intel_pstate_sample(cpu, time); >>> >>> if (sample_taken && !hwp_active) >>> intel_pstate_adjust_busy_pstate(cpu); >>> >>> and (the mainline version of) intel_pstate_sample() returns false when >>> it is called for the first time after setting the update_util hook. >> >> The callsites in scheduler will set time to rq_clock(rq) when trigger >> sample, so when time 0 will be used even if it is set just before >> setting the update_util hook? > > I'm not sure what you mean. > > time=0 is special as it will cause intel_pstate_sample() to return > false on the next invocation.
Sample is driven by cpufreq_update_util() which uses rq_clock(rq) as time parameter, so there is no opportunity to pass time 0 to intel_pstate_sample().
Regards, Wanpeng Li
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