MDEV-9573 'Stop slave' hangs on replication slave

The reason for this is that stop slave takes LOCK_active_mi over the
whole operation while some slave operations will also need LOCK_active_mi
which causes deadlocks.

Fixed by introducing object counting for Master_info and not taking
LOCK_active_mi over stop slave or even stop_all_slaves()

Another benefit of this approach is that it allows:
- Multiple threads can run SHOW SLAVE STATUS at the same time
- START/STOP/RESET/SLAVE STATUS on a slave will not block other slaves
- Simpler interface for handling get_master_info()
- Added some missing unlock of 'log_lock' in error condtions
- Moved rpl_parallel_inactivate_pool(&global_rpl_thread_pool) to end
  of stop_slave() to not have to use LOCK_active_mi inside
  terminate_slave_threads()
- Changed argument for remove_master_info() to Master_info, as we always
  have this available
- Fixed core dump when doing FLUSH TABLES WITH READ LOCK and parallel
  replication. Problem was that waiting for pause_for_ftwrl was not done
  when deleting rpt->current_owner after a force_abort.

1 files changed, 29 insertions, 27 deletions

diff --git a/sql/sql_reload.cc b/sql/sql_reload.cc
index bcf2585ca2a..f9c5757f721 100644
--- a/sql/sql_reload.cc
+++ b/sql/sql_reload.cc
@@ -174,24 +174,20 @@ bool reload_acl_and_cache(THD *thd, unsigned long long options,
       slave is not likely to have the same connection names.
     */
     tmp_write_to_binlog= 0;
-    mysql_mutex_lock(&LOCK_active_mi);
-    if (master_info_index)
+
+    if (!(mi= (get_master_info(&connection_name,
+                               Sql_condition::WARN_LEVEL_ERROR))))
     {
-      if (!(mi= (master_info_index->
-                 get_master_info(&connection_name,
-                                 Sql_condition::WARN_LEVEL_ERROR))))
-      {
-        result= 1;
-      }
-      else
-      {
-        mysql_mutex_lock(&mi->data_lock);
-        if (rotate_relay_log(mi))
-          *write_to_binlog= -1;
-        mysql_mutex_unlock(&mi->data_lock);
-      }
+      result= 1;
+    }
+    else
+    {
+      mysql_mutex_lock(&mi->data_lock);
+      if (rotate_relay_log(mi))
+        *write_to_binlog= -1;
+      mysql_mutex_unlock(&mi->data_lock);
+      mi->release();
     }
-    mysql_mutex_unlock(&LOCK_active_mi);
 #endif
   }
 #ifdef HAVE_QUERY_CACHE
@@ -349,27 +345,33 @@ bool reload_acl_and_cache(THD *thd, unsigned long long options,
    LEX_MASTER_INFO* lex_mi= &thd->lex->mi;
    Master_info *mi;
    tmp_write_to_binlog= 0;
-   mysql_mutex_lock(&LOCK_active_mi);
-   if (master_info_index)
+
+   if (!(mi= get_master_info(&lex_mi->connection_name,
+                             Sql_condition::WARN_LEVEL_ERROR)))
    {
-     if (!(mi= (master_info_index->
-                get_master_info(&lex_mi->connection_name,
-                                Sql_condition::WARN_LEVEL_ERROR))))
-     {
-       result= 1;
-     }
-     else if (reset_slave(thd, mi))
+     result= 1;
+   }
+   else
+   {
+     /* The following will fail if slave is running */
+     if (reset_slave(thd, mi))
      {
+       mi->release();
        /* NOTE: my_error() has been already called by reset_slave(). */
        result= 1;
      }
      else if (mi->connection_name.length && thd->lex->reset_slave_info.all)
      {
        /* If not default connection and 'all' is used */
-       master_info_index->remove_master_info(&mi->connection_name);
+       mi->release();
+       mysql_mutex_lock(&LOCK_active_mi);
+       if (master_info_index->remove_master_info(mi))
+         result= 1;
+       mysql_mutex_unlock(&LOCK_active_mi);
      }
+     else
+       mi->release();
    }
-   mysql_mutex_unlock(&LOCK_active_mi);
  }
 #endif
  if (options & REFRESH_USER_RESOURCES)