locks: Protected racy (read) access of ext_list

Change-Id: Ibf639695ebd99c11c6960c9be82c0cee71b50744
BUG: 905864
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-on: http://review.gluster.org/4458
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>

1 files changed, 18 insertions, 10 deletions

diff --git a/xlators/features/locks/src/common.c b/xlators/features/locks/src/common.c
index cfba16ff735..9c21bddb9e0 100644
--- a/xlators/features/locks/src/common.c
+++ b/xlators/features/locks/src/common.c
@@ -718,22 +718,30 @@ static posix_lock_t *
 first_conflicting_overlap (pl_inode_t *pl_inode, posix_lock_t *lock)
 {
         posix_lock_t *l = NULL;
+        posix_lock_t *conf = NULL;
 
-        list_for_each_entry (l, &pl_inode->ext_list, list) {
-                if (l->blocked)
-                        continue;
-
-                if (locks_overlap (l, lock)) {
-                        if (same_owner (l, lock))
+        pthread_mutex_lock (&pl_inode->mutex);
+        {
+                list_for_each_entry (l, &pl_inode->ext_list, list) {
+                        if (l->blocked)
                                 continue;
 
-                        if ((l->fl_type == F_WRLCK) ||
-                            (lock->fl_type == F_WRLCK))
-                                return l;
+                        if (locks_overlap (l, lock)) {
+                                if (same_owner (l, lock))
+                                        continue;
+
+                                if ((l->fl_type == F_WRLCK) ||
+                                    (lock->fl_type == F_WRLCK)) {
+                                        conf = l;
+                                        goto unlock;
+                                }
+                        }
                 }
         }
+unlock:
+        pthread_mutex_unlock (&pl_inode->mutex);
 
-        return NULL;
+        return conf;
 }
 
 /*