MDEV-9088 Server crashes on shutdown after the second post of feedback report

On shutdown feedback was sending a short report without creating
a THD. At that point current_thd was pointing to the already
destroyed THD from the previous full report.

backport from 10.1:
  commit bfe703a
  Author: Sergei Golubchik <serg@mariadb.org>
  Date:   Tue Feb 3 18:19:56 2015 +0100

      don't let current_thd to point to a destroyed THD

12 files changed, 1 insertions, 55 deletions

diff --git a/sql/events.cc b/sql/events.cc
index 32d194e3bac..75780cd94c5 100644
--- a/sql/events.cc
+++ b/sql/events.cc
@@ -907,10 +907,7 @@ end:
   if (res)
     deinit();
   if (!had_thd)
-  {
     delete thd;
-    set_current_thd(0);
-  }
 
   DBUG_RETURN(res);
 }
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index e52a35bcc8f..e3e331932d0 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -6334,7 +6334,6 @@ void handle_connections_sockets()
 	(void) mysql_socket_close(new_sock);
       }
       delete thd;
-      set_current_thd(0);
       statistic_increment(connection_errors_internal, &LOCK_status);
       continue;
     }
@@ -6449,7 +6448,6 @@ 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 3647520ed4b..63d7d7a0399 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -959,8 +959,6 @@ my_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);
 }
 
@@ -6371,8 +6369,6 @@ my_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 807ec93f4cb..52d5928ea1d 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -9045,7 +9045,6 @@ 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 583abee360f..7a9cdad84f6 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -1645,7 +1645,7 @@ THD::~THD()
     DBUG_ASSERT(status_var.memory_used == 0);  // Ensure everything is freed
   }
 
-  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 dea224398ea..5977cfb8618 100644
--- a/sql/sql_plugin.cc
+++ b/sql/sql_plugin.cc
@@ -1791,9 +1791,7 @@ static void plugin_load(MEM_ROOT *tmp_root)
   table->m_needs_reopen= TRUE;                  // Force close to free memory
   close_mysql_tables(new_thd);
 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 4d22dae1c47..86d1e27a4ef 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 8d5bb2b596d..78d11a6bebf 100644
--- a/sql/sql_servers.cc
+++ b/sql/sql_servers.cc
@@ -177,8 +177,6 @@ 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 ff5c385626a..1e7d4f5e3c6 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -1674,8 +1674,6 @@ void execute_ddl_log_recovery()
   mysql_mutex_unlock(&LOCK_gdl);
   thd->reset_query();
   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 0f9043a77df..74d2f6bc252 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 6486e9b2018..9791e218108 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;
diff --git a/storage/spider/spd_conn.cc b/storage/spider/spd_conn.cc
index 293a209ac68..c5c47064403 100644
--- a/storage/spider/spd_conn.cc
+++ b/storage/spider/spd_conn.cc
@@ -2280,9 +2280,6 @@ void *spider_bg_conn_action(
   if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
   {
     delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-    set_current_thd(NULL);
-#endif
     pthread_mutex_lock(&conn->bg_conn_sync_mutex);
     pthread_cond_signal(&conn->bg_conn_sync_cond);
     pthread_mutex_unlock(&conn->bg_conn_sync_mutex);
@@ -2346,9 +2343,6 @@ void *spider_bg_conn_action(
       spider_free_trx(trx, TRUE);
       /* lex_end(thd->lex); */
       delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-      set_current_thd(NULL);
-#endif
       pthread_mutex_lock(&conn->bg_conn_sync_mutex);
       pthread_cond_signal(&conn->bg_conn_sync_cond);
       pthread_mutex_unlock(&conn->bg_conn_mutex);
@@ -2799,9 +2793,6 @@ void *spider_bg_sts_action(
   if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
   {
     delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-    set_current_thd(NULL);
-#endif
     share->bg_sts_thd_wait = FALSE;
     share->bg_sts_kill = FALSE;
     share->bg_sts_init = FALSE;
@@ -2867,9 +2858,6 @@ void *spider_bg_sts_action(
     }
     spider_free_trx(trx, TRUE);
     delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-    set_current_thd(NULL);
-#endif
     share->bg_sts_thd_wait = FALSE;
     share->bg_sts_kill = FALSE;
     share->bg_sts_init = FALSE;
@@ -2903,9 +2891,6 @@ void *spider_bg_sts_action(
       }
       spider_free_trx(trx, TRUE);
       delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-      set_current_thd(NULL);
-#endif
       pthread_cond_signal(&share->bg_sts_sync_cond);
       pthread_mutex_unlock(&share->sts_mutex);
 #if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
@@ -3190,9 +3175,6 @@ void *spider_bg_crd_action(
   if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
   {
     delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-    set_current_thd(NULL);
-#endif
     share->bg_crd_thd_wait = FALSE;
     share->bg_crd_kill = FALSE;
     share->bg_crd_init = FALSE;
@@ -3262,9 +3244,6 @@ void *spider_bg_crd_action(
     }
     spider_free_trx(trx, TRUE);
     delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-    set_current_thd(NULL);
-#endif
     share->bg_crd_thd_wait = FALSE;
     share->bg_crd_kill = FALSE;
     share->bg_crd_init = FALSE;
@@ -3298,9 +3277,6 @@ void *spider_bg_crd_action(
       }
       spider_free_trx(trx, TRUE);
       delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-      set_current_thd(NULL);
-#endif
       pthread_cond_signal(&share->bg_crd_sync_cond);
       pthread_mutex_unlock(&share->crd_mutex);
 #if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
@@ -3688,9 +3664,6 @@ void *spider_bg_mon_action(
   if (!(trx = spider_get_trx(thd, FALSE, &error_num)))
   {
     delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-    set_current_thd(NULL);
-#endif
     share->bg_mon_kill = FALSE;
     share->bg_mon_init = FALSE;
     pthread_cond_signal(&share->bg_mon_conds[link_idx]);
@@ -3734,9 +3707,6 @@ void *spider_bg_mon_action(
       pthread_mutex_unlock(&share->bg_mon_mutexes[link_idx]);
       spider_free_trx(trx, TRUE);
       delete thd;
-#if defined(MARIADB_BASE_VERSION) && MYSQL_VERSION_ID >= 100000
-      set_current_thd(NULL);
-#endif
 #if !defined(MYSQL_DYNAMIC_PLUGIN) || !defined(_WIN32)
       my_pthread_setspecific_ptr(THR_THD, NULL);
 #endif