[PATCH RFC 06/10] 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.

Signed-off-by: Kan Liang <kan.li...@intel.com>
---
 tools/perf/util/comm.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
index 7bc981b..1bdfef1 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 <pthread.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 pthread_mutex_t comm_str_lock = PTHREAD_MUTEX_INITIALIZER;
 
 static struct comm_str *comm_str__get(struct comm_str *cs)
 {
@@ -24,11 +26,13 @@ static struct comm_str *comm_str__get(struct comm_str *cs)
 
 static void comm_str__put(struct comm_str *cs)
 {
+       pthread_mutex_lock(&comm_str_lock);
        if (cs && refcount_dec_and_test(&cs->refcnt)) {
                rb_erase(&cs->rb_node, &comm_str_root);
                zfree(&cs->str);
                free(cs);
        }
+       pthread_mutex_unlock(&comm_str_lock);
 }
 
 static struct comm_str *comm_str__alloc(const char *str)
@@ -52,18 +56,22 @@ static struct comm_str *comm_str__alloc(const char *str)
 
 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;
        struct comm_str *iter, *new;
+       struct rb_node **p;
        int cmp;
 
+       pthread_mutex_lock(&comm_str_lock);
+       p = &root->rb_node;
        while (*p != NULL) {
                parent = *p;
                iter = rb_entry(parent, struct comm_str, rb_node);
 
                cmp = strcmp(str, iter->str);
-               if (!cmp)
-                       return comm_str__get(iter);
+               if (!cmp) {
+                       new = comm_str__get(iter);
+                       goto unlock;
+               }
 
                if (cmp < 0)
                        p = &(*p)->rb_left;
@@ -73,11 +81,13 @@ static struct comm_str *comm_str__findnew(const char *str, 
struct rb_root *root)
 
        new = comm_str__alloc(str);
        if (!new)
-               return NULL;
+               goto unlock;
 
        rb_link_node(&new->rb_node, parent, p);
        rb_insert_color(&new->rb_node, root);
 
+unlock:
+       pthread_mutex_unlock(&comm_str_lock);
        return new;
 }
 
-- 
2.5.5