linux-kernel - [PATCH] perf map: remove extra indirection from map_

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Date:   Fri, 23 Nov 2018 02:42:39 -0800
From:   Eric Saint-Etienne <eric.saint.etienne@...cle.com>
To:     Linux Kernel <linux-kernel@...r.kernel.org>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.co>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Eric Saint-Etienne <eric.saintetienne@...il.com>
Subject: [PATCH] perf map: remove extra indirection from map__find()

A double pointer is used in map__find() where a single pointer is enough
because the function doesn't affect the rbtree and the rbtree is locked.

Signed-off-by: Eric Saint-Etienne <eric.saint.etienne@...cle.com>
---
 tools/perf/util/map.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 354e545..3dac766 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -846,19 +846,18 @@ void maps__remove(struct maps *maps, struct map *map)
 
 struct map *maps__find(struct maps *maps, u64 ip)
 {
-	struct rb_node **p, *parent = NULL;
+	struct rb_node *p;
 	struct map *m;
 
 	down_read(&maps->lock);
 
-	p = &maps->entries.rb_node;
-	while (*p != NULL) {
-		parent = *p;
-		m = rb_entry(parent, struct map, rb_node);
+	p = maps->entries.rb_node;
+	while (p != NULL) {
+		m = rb_entry(p, struct map, rb_node);
 		if (ip < m->start)
-			p = &(*p)->rb_left;
+			p = p->rb_left;
 		else if (ip >= m->end)
-			p = &(*p)->rb_right;
+			p = p->rb_right;
 		else
 			goto out;
 	}
-- 
1.8.3.1