[PATCH RFC V4 2/6] perf tools: lock to protect comm_str rb tree

[kan . liang]

From: Kan Liang <kan.li...@intel.com>

Add comm_str_lock to protect comm_str rb tree.

The lock is only needed for multithreaded code, so using mutex wrappers
provided by perf tool.

Signed-off-by: Kan Liang <kan.li...@intel.com>
---
 tools/perf/util/comm.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
index 7bc981b..756a9c1 100644
--- a/tools/perf/util/comm.c
+++ b/tools/perf/util/comm.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <linux/refcount.h>
+#include "rwsem.h"
 
 struct comm_str {
        char *str;
@@ -14,6 +15,7 @@ struct comm_str {
 
 /* Should perhaps be moved to struct machine */
 static struct rb_root comm_str_root;
+static struct rw_semaphore comm_str_lock = {.lock = 
PTHREAD_RWLOCK_INITIALIZER,};
 
 static struct comm_str *comm_str__get(struct comm_str *cs)
 {
@@ -25,7 +27,9 @@ static struct comm_str *comm_str__get(struct comm_str *cs)
 static void comm_str__put(struct comm_str *cs)
 {
        if (cs && refcount_dec_and_test(&cs->refcnt)) {
+               down_write(&comm_str_lock);
                rb_erase(&cs->rb_node, &comm_str_root);
+               up_write(&comm_str_lock);
                zfree(&cs->str);
                free(cs);
        }
@@ -50,7 +54,8 @@ static struct comm_str *comm_str__alloc(const char *str)
        return cs;
 }
 
-static struct comm_str *comm_str__findnew(const char *str, struct rb_root 
*root)
+static
+struct comm_str *__comm_str__findnew(const char *str, struct rb_root *root)
 {
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent = NULL;
@@ -81,6 +86,17 @@ static struct comm_str *comm_str__findnew(const char *str, 
struct rb_root *root)
        return new;
 }
 
+static struct comm_str *comm_str__findnew(const char *str, struct rb_root 
*root)
+{
+       struct comm_str *cs;
+
+       down_write(&comm_str_lock);
+       cs = __comm_str__findnew(str, root);
+       up_write(&comm_str_lock);
+
+       return cs;
+}
+
 struct comm *comm__new(const char *str, u64 timestamp, bool exec)
 {
        struct comm *comm = zalloc(sizeof(*comm));
-- 
2.5.5