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perf, x86: Fix double enable calls 

hw_perf_enable() would enable already enabled events.

This causes problems with code that assumes that ->enable/->disable calls
are balanced (like the LBR code does).

What happens is that events that were already running and left in place
would get enabled again.

Avoid this by only enabling new events that match their previous
assignment.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: paulus@samba.org
Cc: eranian@google.com
Cc: robert.richter@amd.com
Cc: fweisbec@gmail.com
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-03-06 13:24:58 +01:00 committed by Ingo Molnar
parent 19925ce778
commit f3d46b2e6f
1 changed files with 4 additions and 0 deletions
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4
arch/x86/kernel/cpu/perf_event.c
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@ -835,6 +835,10 @@ void hw_perf_enable(void)
event = cpuc->event_list[i];
hwc = &event->hw;
if (i < n_running &&
match_prev_assignment(hwc, cpuc, i))
continue;
if (hwc->idx == -1)
x86_assign_hw_event(event, cpuc, i);