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;