linux-kernel - [PATCH] perf: fixing variable initialisation

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Date:	Mon, 27 Jul 2015 16:41:19 -0600
From:	Mathieu Poirier <mathieu.poirier@...aro.org>
To:	a.p.zijlstra@...llo.nl, mingo@...hat.com, acme@...nel.org,
	alexander.shishkin@...ux.intel.com
Cc:	linux-kernel@...r.kernel.org, mathieu.poirier@...aro.org
Subject: [PATCH] perf: fixing variable initialisation

Variable 'max_order' needs to be initialised to log2 of the
number of pages invariant of the no scather-gather PMU option.
Otherwise 'rb_alloc_aux_page' gets an order that is equal to
'0', which prevents the private page information to be set
properly.

Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
---
 kernel/events/ring_buffer.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 96472824a752..bd3da7bebe9e 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -449,18 +449,18 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
 {
 	bool overwrite = !(flags & RING_BUFFER_WRITABLE);
 	int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
-	int ret = -ENOMEM, max_order = 0;
+	int ret = -ENOMEM, max_order;
 
 	if (!has_aux(event))
 		return -ENOTSUPP;
 
-	if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
-		/*
-		 * We need to start with the max_order that fits in nr_pages,
-		 * not the other way around, hence ilog2() and not get_order.
-		 */
-		max_order = ilog2(nr_pages);
+	/*
+	 * We need to start with the max_order that fits in nr_pages,
+	 * not the other way around, hence ilog2() and not get_order.
+	 */
+	max_order = ilog2(nr_pages);
 
+	if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) {
 		/*
 		 * PMU requests more than one contiguous chunks of memory
 		 * for SW double buffering
-- 
1.9.1

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