From: Stephane Eranian <eranian@google.com>
Date: Mon, 1 Feb 2010 12:50:01 +0000 (+0200)
Subject: perf_events, x86: Fix bug in hw_perf_enable()
X-Git-Tag: v2.6.34-rc1~197^2~43
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=447a194b393f32699607fd99617a40abd6a95114;p=pandora-kernel.git

perf_events, x86: Fix bug in hw_perf_enable()

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>
---

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