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perf_events, x86: Fix bug in hw_perf_enable()

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We cannot assume that because hwc->idx == assign[i], we can avoid
reprogramming the counter in hw_perf_enable().

The event may have been scheduled out and another event may have been
programmed into this counter. Thus, we need a more robust way of
verifying if the counter still contains config/data related to an event.

This patch adds a generation number to each counter on each cpu. Using
this mechanism we can verify reliabilty whether the content of a counter
corresponds to an event.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4b66dc67.0b38560a.1635.ffffae18@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Stephane Eranian
2010-02-01 14:50:01 +02:00
committed by Ingo Molnar
parent fce877e3a4
commit 447a194b39
2 changed files with 30 additions and 6 deletions
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2
include/linux/perf_event.h
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@@ -478,9 +478,11 @@ struct hw_perf_event {
union {
struct { /* hardware */
u64 config;
u64 last_tag;
unsigned long config_base;
unsigned long event_base;
int idx;
int last_cpu;
};
struct { /* software */
s64 remaining;