Bug #26019 - valgrind warning ndbcluster_log_schema_op/safe_mutex_lock invalid read

protect the setting of ndb_schema_share = NULL with a mutex


sql/ha_ndbcluster_binlog.cc:
  protect the setting of ndb_schema_share = NULL with a mutec

sql/ha_ndbcluster_binlog.cc

@@ -97,6 +97,7 @@ static ulonglong ndb_latest_received_binlog_epoch= 0;
 
 NDB_SHARE *ndb_apply_status_share= 0;
 NDB_SHARE *ndb_schema_share= 0;
+pthread_mutex_t ndb_schema_share_mutex;
 
 /* Schema object distribution handling */
 HASH ndb_schema_objects;
@@ -621,6 +622,7 @@ static int ndbcluster_binlog_end(THD *thd)
 
   pthread_mutex_destroy(&injector_mutex);
   pthread_cond_destroy(&injector_cond);
+  pthread_mutex_destroy(&ndb_schema_share_mutex);
 #endif
   DBUG_RETURN(0);
 }
@@ -1271,6 +1273,16 @@ int ndbcluster_log_schema_op(THD *thd, NDB_SHARE *share,
     int no_storage_nodes= g_ndb_cluster_connection->no_db_nodes();
     bitmap_init(&schema_subscribers, bitbuf, sizeof(bitbuf)*8, FALSE);
     bitmap_set_all(&schema_subscribers);
+
+    /* begin protect ndb_schema_share */
+    pthread_mutex_lock(&ndb_schema_share_mutex);
+    if (ndb_schema_share == 0)
+    {
+      pthread_mutex_unlock(&ndb_schema_share_mutex);
+      if (ndb_schema_object)
+        ndb_free_schema_object(&ndb_schema_object, FALSE);
+      DBUG_RETURN(0);    
+    }
     (void) pthread_mutex_lock(&ndb_schema_share->mutex);
     for (i= 0; i < no_storage_nodes; i++)
     {
@@ -1283,6 +1295,9 @@ int ndbcluster_log_schema_op(THD *thd, NDB_SHARE *share,
       }
     }
     (void) pthread_mutex_unlock(&ndb_schema_share->mutex);
+    pthread_mutex_unlock(&ndb_schema_share_mutex);
+    /* end protect ndb_schema_share */
+
     if (updated)
     {
       bitmap_clear_bit(&schema_subscribers, node_id);
@@ -1478,6 +1493,14 @@ int ndbcluster_log_schema_op(THD *thd, NDB_SHARE *share,
                                       &abstime);
       if (thd->killed)
         break;
+
+      /* begin protect ndb_schema_share */
+      pthread_mutex_lock(&ndb_schema_share_mutex);
+      if (ndb_schema_share == 0)
+      {
+        pthread_mutex_unlock(&ndb_schema_share_mutex);
+        break;
+      }
       (void) pthread_mutex_lock(&ndb_schema_share->mutex);
       for (i= 0; i < no_storage_nodes; i++)
       {
@@ -1487,6 +1510,8 @@ int ndbcluster_log_schema_op(THD *thd, NDB_SHARE *share,
           bitmap_intersect(&schema_subscribers, tmp);
       }
       (void) pthread_mutex_unlock(&ndb_schema_share->mutex);
+      pthread_mutex_unlock(&ndb_schema_share_mutex);
+      /* end protect ndb_schema_share */
 
       /* remove any unsubscribed from ndb_schema_object->slock */
       bitmap_intersect(&ndb_schema_object->slock_bitmap, &schema_subscribers);
@@ -1910,8 +1935,14 @@ ndb_binlog_thread_handle_schema_event(THD *thd, Ndb *ndb,
           ndb_binlog_tables_inited && ndb_binlog_running)
         sql_print_information("NDB Binlog: ndb tables initially "
                               "read only on reconnect.");
+
+      /* begin protect ndb_schema_share */
+      pthread_mutex_lock(&ndb_schema_share_mutex);
       free_share(&ndb_schema_share);
       ndb_schema_share= 0;
+      pthread_mutex_unlock(&ndb_schema_share_mutex);
+      /* end protect ndb_schema_share */
+
       close_cached_tables((THD*) 0, 0, (TABLE_LIST*) 0, FALSE);
       // fall through
     case NDBEVENT::TE_ALTER:
@@ -2278,6 +2309,7 @@ int ndbcluster_binlog_start()
 
   pthread_mutex_init(&injector_mutex, MY_MUTEX_INIT_FAST);
   pthread_cond_init(&injector_cond, NULL);
+  pthread_mutex_init(&ndb_schema_share_mutex, MY_MUTEX_INIT_FAST);
 
   /* Create injector thread */
   if (pthread_create(&ndb_binlog_thread, &connection_attrib,
@@ -3966,8 +3998,12 @@ pthread_handler_t ndb_binlog_thread_func(void *arg)
   }
   if (ndb_schema_share)
   {
+    /* begin protect ndb_schema_share */
+    pthread_mutex_lock(&ndb_schema_share_mutex);
     free_share(&ndb_schema_share);
     ndb_schema_share= 0;
+    pthread_mutex_unlock(&ndb_schema_share_mutex);
+    /* end protect ndb_schema_share */
   }
 
   /* remove all event operations */