powerpc/perf_event: Fix for power_pmu_disable()
authorMatt Evans <matt@ozlabs.org>
Mon, 5 Jul 2010 17:36:32 +0000 (17:36 +0000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Thu, 8 Jul 2010 08:11:37 +0000 (18:11 +1000)
commit219a92a4c40db2fac604f63bce9a5a3fe1967879
treea02b36dca8a413ca6793b316afbd7e5592d7ae7b
parent2aa72f612144a0a7d4b0b22ae7c122692ac6a013
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>
arch/powerpc/kernel/perf_event.c