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.

1 files changed, 15 insertions, 6 deletions

diff --git a/sql/slave.cc b/sql/slave.cc
index 36d28382c56..70b1c5b025e 100644
--- a/sql/slave.cc
+++ b/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;