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23 October 2021, 00:29:24 UTC
Revision 219a92a4c40db2fac604f63bce9a5a3fe1967879 authored by Matt Evans on 05 July 2010, 17:36:32 UTC, committed by Benjamin Herrenschmidt on 08 July 2010, 08:11:37 UTC 
powerpc/perf_event: Fix for power_pmu_disable()
 
When power_pmu_disable() removes the given event from a particular index into
cpuhw->event[], it shuffles down higher event[] entries.  But, this array is
paired with cpuhw->events[] and cpuhw->flags[] so should shuffle them
similarly.

If these arrays get out of sync, code such as power_check_constraints() will
fail.  This caused a bug where events were temporarily disabled and then failed
to be re-enabled; subsequent code tried to write_pmc() with its (disabled) idx
of 0, causing a message "oops trying to write PMC0".  This triggers this bug on
POWER7, running a miss-heavy test:

  perf record -e L1-dcache-load-misses -e L1-dcache-store-misses ./misstest

Signed-off-by: Matt Evans <matt@ozlabs.org>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
1 parent 2aa72f6
History
Tip revision: 219a92a4c40db2fac604f63bce9a5a3fe1967879 authored by Matt Evans on 05 July 2010, 17:36:32 UTC
powerpc/perf_event: Fix for power_pmu_disable()
Tip revision: 219a92a
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