Wait for slave threads to start during startup

- Before this patch during startup all slave threads was started without
  any check that they had started properly.
- If one did a START SLAVE, STOP SLAVE or CHANGE MASTER as first command to the server
  there was a chance that server could access structures that where not
  properly  initialized which could lead to crashes in
  Log_event::read_log_event
- Fixed by waiting for slave threads to start up properly also during
  server startup, like we do with START SLAVE.

Author: montywi

sql/rpl_mi.cc

@@ -949,6 +949,7 @@ bool Master_info_index::init_all_master_info()
   int err_num= 0, succ_num= 0; // The number of success read Master_info
   char sign[MAX_CONNECTION_NAME+1];
   File index_file_nr;
+  THD *thd;
   DBUG_ENTER("init_all_master_info");
 
   DBUG_ASSERT(master_info_index);
@@ -980,6 +981,10 @@ bool Master_info_index::init_all_master_info()
     DBUG_RETURN(1);
   }
 
+  thd= new THD;  /* Needed by start_slave_threads */
+  thd->thread_stack= (char*) &thd;
+  thd->store_globals();
+
   reinit_io_cache(&index_file, READ_CACHE, 0L,0,0);
   while (!init_strvar_from_file(sign, sizeof(sign),
                                 &index_file, NULL))
@@ -995,7 +1000,7 @@ bool Master_info_index::init_all_master_info()
         mi->error())
     {
       delete mi;
-      DBUG_RETURN(1);
+      goto error;
     }
 
     init_thread_mask(&thread_mask,mi,0 /*not inverse*/);
@@ -1024,7 +1029,7 @@ bool Master_info_index::init_all_master_info()
       {
         /* Master_info is not in HASH; Add it */
         if (master_info_index->add_master_info(mi, FALSE))
-          DBUG_RETURN(1);
+          goto error;
         succ_num++;
         mi->unlock_slave_threads();
       }
@@ -1059,13 +1064,13 @@ bool Master_info_index::init_all_master_info()
 
       /* Master_info was not registered; add it */
       if (master_info_index->add_master_info(mi, FALSE))
-        DBUG_RETURN(1);
+        goto error;
       succ_num++;
 
       if (!opt_skip_slave_start)
       {
         if (start_slave_threads(1 /* need mutex */,
-              0 /* no wait for start*/,
+              1 /* wait for start*/,
               mi,
               buf_master_info_file,
               buf_relay_log_info_file,
@@ -1084,23 +1089,28 @@ bool Master_info_index::init_all_master_info()
       mi->unlock_slave_threads();
     }
   }
+  thd->reset_globals();
+  delete thd;
 
   if (!err_num) // No Error on read Master_info
   {
     if (global_system_variables.log_warnings > 1)
       sql_print_information("Reading of all Master_info entries succeded");
     DBUG_RETURN(0);
   }
-  else if (succ_num) // Have some Error and some Success
+  if (succ_num) // Have some Error and some Success
   {
     sql_print_warning("Reading of some Master_info entries failed");
     DBUG_RETURN(2);
   }
-  else // All failed
-  {
-    sql_print_error("Reading of all Master_info entries failed!");
-    DBUG_RETURN(1);
-  }
+
+  sql_print_error("Reading of all Master_info entries failed!");
+  DBUG_RETURN(1);
+
+error:
+  thd->reset_globals();
+  delete thd;
+  DBUG_RETURN(1);
 }
 
 

sql/slave.cc

@@ -421,12 +421,21 @@ int init_slave()
 
   if (active_mi->host[0] && !opt_skip_slave_start)
   {
-    if (start_slave_threads(1 /* need mutex */,
-                            0 /* no wait for start*/,
-                            active_mi,
-                            master_info_file,
-                            relay_log_info_file,
-                            SLAVE_IO | SLAVE_SQL))
+    int error;
+    THD *thd= new THD;
+    thd->thread_stack= (char*) &thd;
+    thd->store_globals();
+
+    error= start_slave_threads(1 /* need mutex */,
+                               1 /* wait for start*/,
+                               active_mi,
+                               master_info_file,
+                               relay_log_info_file,
+                               SLAVE_IO | SLAVE_SQL);
+
+    thd->reset_globals();
+    delete thd;
+    if (error)
     {
       sql_print_error("Failed to create slave threads");
       goto err;