don't let current_thd to point to a destroyed THD

* reset current_thd in THD::~THD, otherwise my_malloc_size_cb_func()
  might access THD after it was destroyed.
* remove now redundant set_current_thd(0) calls that follow delete thd.

11 files changed, 1 insertions, 25 deletions

diff --git a/sql/events.cc b/sql/events.cc
index c4a7f63dbbc..7268686a33e 100644
--- a/sql/events.cc
+++ b/sql/events.cc
@@ -896,8 +896,6 @@ end:
     delete scheduler;
   }
   delete thd;
-  /* Remember that we don't have a THD */
-  set_current_thd(0);
 
   DBUG_RETURN(res);
 }
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index a94b696281b..423d07b02cd 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -2973,8 +2973,6 @@ bool one_thread_per_connection_end(THD *thd, bool put_in_cache)
   const bool wsrep_applier= IF_WSREP(thd->wsrep_applier, false);
 
   unlink_thd(thd);
-  /* Mark that current_thd is not valid anymore */
-  set_current_thd(0);
 
   if (put_in_cache && cache_thread() && !wsrep_applier)
     DBUG_RETURN(0);                             // Thread is reused
@@ -6555,7 +6553,6 @@ void handle_connections_sockets()
 	(void) mysql_socket_close(new_sock);
       }
       delete thd;
-      set_current_thd(0);
       statistic_increment(connection_errors_internal, &LOCK_status);
       continue;
     }
@@ -6670,7 +6667,6 @@ pthread_handler_t handle_connections_namedpipes(void *arg)
     {
       close_connection(thd, ER_OUT_OF_RESOURCES);
       delete thd;
-      set_current_thd(0);
       continue;
     }
     /* Host is unknown */
diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index c8714423933..96fff6d6763 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -1140,8 +1140,6 @@ bool acl_init(bool dont_read_acl_tables)
   */
   return_val= acl_reload(thd);
   delete thd;
-  /* Remember that we don't have a THD */
-  set_current_thd(0);
   DBUG_RETURN(return_val);
 }
 
@@ -6556,8 +6554,6 @@ bool grant_init()
   thd->store_globals();
   return_val=  grant_reload(thd);
   delete thd;
-  /* Remember that we don't have a THD */
-  set_current_thd(0);
   DBUG_RETURN(return_val);
 }
 
diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index 70529b207b1..a5d7881707c 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -9024,7 +9024,6 @@ my_bool mysql_rm_tmp_tables(void)
     my_dirend(dirp);
   }
   delete thd;
-  set_current_thd(0);
   DBUG_RETURN(0);
 }
 
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index aaff36767da..7e26c77afcd 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1712,7 +1712,7 @@ THD::~THD()
     DBUG_ASSERT(status_var.local_memory_used == 0);
   }
 
-  set_current_thd(orig_thd);
+  set_current_thd(orig_thd == this ? 0 : orig_thd);
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/sql_plugin.cc b/sql/sql_plugin.cc
index e9a0f138212..900167c1fab 100644
--- a/sql/sql_plugin.cc
+++ b/sql/sql_plugin.cc
@@ -1775,7 +1775,6 @@ static void plugin_load(MEM_ROOT *tmp_root)
 end:
   /* Remember that we don't have a THD */
   delete new_thd;
-  set_current_thd(0);
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/sql_reload.cc b/sql/sql_reload.cc
index fe494c760dc..6fc0e0024af 100644
--- a/sql/sql_reload.cc
+++ b/sql/sql_reload.cc
@@ -98,8 +98,6 @@ bool reload_acl_and_cache(THD *thd, unsigned long long options,
     if (tmp_thd)
     {
       delete tmp_thd;
-      /* Remember that we don't have a THD */
-      set_current_thd(0);
       thd= 0;
     }
     reset_mqh((LEX_USER *)NULL, TRUE);
diff --git a/sql/sql_servers.cc b/sql/sql_servers.cc
index 7f4d70a6b43..9b944662545 100644
--- a/sql/sql_servers.cc
+++ b/sql/sql_servers.cc
@@ -173,8 +173,6 @@ bool servers_init(bool dont_read_servers_table)
   */
   return_val= servers_reload(thd);
   delete thd;
-  /* Remember that we don't have a THD */
-  set_current_thd(0);
 
 end:
   DBUG_RETURN(return_val);
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index ef6252c496b..e9a1ae981dc 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -1674,8 +1674,6 @@ void execute_ddl_log_recovery()
   global_ddl_log.recovery_phase= FALSE;
   mysql_mutex_unlock(&LOCK_gdl);
   delete thd;
-  /* Remember that we don't have a THD */
-  set_current_thd(0);
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/sql_udf.cc b/sql/sql_udf.cc
index 2354f120041..d266e8f6bc7 100644
--- a/sql/sql_udf.cc
+++ b/sql/sql_udf.cc
@@ -258,8 +258,6 @@ void udf_init()
 end:
   close_mysql_tables(new_thd);
   delete new_thd;
-  /* Remember that we don't have a THD */
-  set_current_thd(0);
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/tztime.cc b/sql/tztime.cc
index 24e61588a06..1cb1f5a0d5c 100644
--- a/sql/tztime.cc
+++ b/sql/tztime.cc
@@ -1803,11 +1803,7 @@ end:
   if (org_thd)
     org_thd->store_globals();			/* purecov: inspected */
   else
-  {
-    /* Remember that we don't have a THD */
-    set_current_thd(0);
     my_pthread_setspecific_ptr(THR_MALLOC,  0);
-  }
   
   default_tz= default_tz_name ? global_system_variables.time_zone
                               : my_tz_SYSTEM;