linux-kernel - [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values

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Message-Id: <1367827480-5375-1-git-send-email-khandual@linux.vnet.ibm.com>
Date:	Mon,  6 May 2013 13:34:40 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Cc:	michael@...erman.id.au, mikey@...ling.org, benh@...nel.crashing.org
Subject: [PATCH] powerpc, perf: Clear out branch entries to avoid any previous stale values

The 'to' field inside branch entries might contain stale values from previous
PMU interrupt instances which had indirect branches. So clear all the values
before reading a fresh set of BHRB entries after a PMU interrupt.

Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
---
 arch/powerpc/perf/core-book3s.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index c627843..09db68d 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -1590,6 +1590,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
 		if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
 			struct cpu_hw_events *cpuhw;
 			cpuhw = &__get_cpu_var(cpu_hw_events);
+			memset(cpuhw->bhrb_entries, 0,
+				sizeof(struct perf_branch_entry) * BHRB_MAX_ENTRIES);
 			power_pmu_bhrb_read(cpuhw);
 			data.br_stack = &cpuhw->bhrb_stack;
 		}
-- 
1.7.11.7

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