MDEV#4109: Galera: Valgrind warnings "blocks are still

           reachable" in wsrep_init_startup on MTR tests

The initialization & de-initialization of wsrep plugin is solely
controlled by wsrep_on system variable. Now, as wsrep_on is ON by
default, the plugin gets initialized during server start. However,
there would be a leakage in case wsrep_on is turned off before plugin's
deinitialization (while server is shutting down) takes place, in which
case the deinit routine will not be invoked.

In this particular case, wsrep_on is turned off as no wsrep provider
has been specified & thus the valgrind warnings.

Fixed by introducing a flag which tracks and now controls the
(de|)initialization of the wsrep plugin instead on wsrep_on.
Added necessary asserts.

main.connect                             [ pass ]  16534
valgrind_report                          [ pass ]

sql/mysqld.cc

@@ -1751,7 +1751,8 @@ static void __cdecl kill_server(int sig_ptr)
 
   close_connections();
 #ifdef WITH_WSREP
-  if (WSREP_ON) wsrep_deinit();
+  if (wsrep_inited == 1)
+    wsrep_deinit();
 #endif
   if (sig != MYSQL_KILL_SIGNAL &&
       sig != 0)

sql/wsrep_mysqld.cc

@@ -56,6 +56,11 @@ my_bool wsrep_desync                   = 0; // desynchronize the node from the c
  * End configuration options
  */
 
+/*
+ * Other wsrep global variables.
+ */
+my_bool wsrep_inited                   = 0; // initialized ?
+
 static const wsrep_uuid_t cluster_uuid = WSREP_UUID_UNDEFINED;
 const wsrep_uuid_t* wsrep_cluster_uuid()
 {
@@ -414,6 +419,7 @@ static void wsrep_init_position()
 int wsrep_init()
 {
   int rcode= -1;
+  DBUG_ASSERT(wsrep_inited == 0);
 
   wsrep_ready_set(FALSE);
   assert(wsrep_provider);
@@ -442,6 +448,7 @@ int wsrep_init()
   {
     // enable normal operation in case no provider is specified
     wsrep_ready_set(TRUE);
+    wsrep_inited= 1;
     global_system_variables.wsrep_on = 0;
     return 0;
   }
@@ -565,6 +572,8 @@ int wsrep_init()
     WSREP_ERROR("wsrep::init() failed: %d, must shutdown", rcode);
     free(wsrep);
     wsrep = NULL;
+  } else {
+    wsrep_inited= 1;
   }
 
   return rcode;
@@ -595,6 +604,7 @@ void wsrep_init_startup (bool first)
 
 void wsrep_deinit()
 {
+  DBUG_ASSERT(wsrep_inited == 1);
   wsrep_unload(wsrep);
   wsrep= 0;
   provider_name[0]=    '\0';
@@ -603,6 +613,7 @@ void wsrep_deinit()
 
   delete wsrep_format_desc;
   wsrep_format_desc= NULL;
+  wsrep_inited= 0;
 }
 
 void wsrep_recover()

sql/wsrep_mysqld.h

@@ -117,6 +117,9 @@ extern const char* wsrep_provider_vendor;
 extern int         wsrep_show_status(THD *thd, SHOW_VAR *var, char *buff);
 extern void        wsrep_free_status(THD *thd);
 
+// Other wsrep global variables
+extern my_bool     wsrep_inited; // whether wsrep is initialized ?
+
 #define WSREP_SST_ADDRESS_AUTO   "AUTO"
 #define WSREP_NODE_INCOMING_AUTO "AUTO"
 

sql/wsrep_var.cc

@@ -247,7 +247,8 @@ bool wsrep_provider_update (sys_var *self, THD* thd, enum_var_type type)
   wsrep_stop_replication(thd);
   mysql_mutex_lock(&LOCK_global_system_variables);
 
-  wsrep_deinit();
+  if (wsrep_inited == 1)
+    wsrep_deinit();
 
   char* tmp= strdup(wsrep_provider); // wsrep_init() rewrites provider 
                                      //when fails