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s390/cpumf: cpum_cf PMU displays invalid value after hotplug remove
commit9d48c7afed
upstream. When a CPU is hotplugged while the perf stat -e cycles command is running, a wrong (very large) value is displayed immediately after the CPU removal: Check the values, shouldn't be too high as in time counts unit events 1.001101919 29261846 cycles 2.002454499 17523405 cycles 3.003659292 24361161 cycles 4.004816983 18446744073638406144 cycles 5.005671647 <not counted> cycles ... The CPU hotplug off took place after 3 seconds. The issue is the read of the event count value after 4 seconds when the CPU is not available and the read of the counter returns an error. This is treated as a counter value of zero. This results in a very large value (0 - previous_value). Fix this by detecting the hotplugged off CPU and report 0 instead of a very large number. Cc: stable@vger.kernel.org Fixes:a029a4eab3
("s390/cpumf: Allow concurrent access for CPU Measurement Counter Facility") Reported-by: Sumanth Korikkar <sumanthk@linux.ibm.com> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com> Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 3 additions and 1 deletions
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@ -687,8 +687,10 @@ static void cpumf_pmu_stop(struct perf_event *event, int flags)
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false);
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if (cfdiag_diffctr(cpuhw, event->hw.config_base))
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cfdiag_push_sample(event, cpuhw);
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} else
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} else if (cpuhw->flags & PMU_F_RESERVED) {
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/* Only update when PMU not hotplugged off */
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hw_perf_event_update(event);
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}
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hwc->state |= PERF_HES_UPTODATE;
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}
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}
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