fix for thread getting stuck after BF ABORT (#1362)

- Fixes a situation in which a thread gets BF aborted and does not send the reply back to
  the client, even though the connection is still alive. That caused
  both sides to hang waiting for the next message. Now we explicitly
  check that the connection is still alive.
- MTR test for the above
- Replaced thd->killed assignments to thd->reset_kill_query where applicable.

2 files changed, 19 insertions, 15 deletions

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 4e04ddf544f..c0b78ead6d6 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -1829,8 +1829,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
       {
         WSREP_DEBUG("Deadlock error for: %s", thd->query());
         mysql_mutex_lock(&thd->LOCK_thd_data);
-        thd->killed               = NOT_KILLED;
-        thd->mysys_var->abort     = 0;
+        thd->reset_kill_query();
         thd->wsrep_retry_counter  = 0;
         mysql_mutex_unlock(&thd->LOCK_thd_data);
         goto dispatch_end;
@@ -1933,8 +1932,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
         {
           WSREP_DEBUG("Deadlock error for: %s", thd->query());
           mysql_mutex_lock(&thd->LOCK_thd_data);
-          thd->killed               = NOT_KILLED;
-          thd->mysys_var->abort     = 0;
+          thd->reset_kill_query();
           thd->wsrep_retry_counter  = 0;
           mysql_mutex_unlock(&thd->LOCK_thd_data);
 
@@ -2410,13 +2408,11 @@ dispatch_end:
     */
     DBUG_ASSERT((command != COM_QUIT && command != COM_STMT_CLOSE)
                   || thd->get_stmt_da()->is_disabled());
+    DBUG_ASSERT(thd->wsrep_trx().state() != wsrep::transaction::s_replaying);
     /* wsrep BF abort in query exec phase */
-    mysql_mutex_lock(&thd->LOCK_thd_data);
-    do_end_of_statement=
-      thd->wsrep_trx().state() != wsrep::transaction::s_replaying
-      && !thd->killed;
-
-    mysql_mutex_unlock(&thd->LOCK_thd_data);
+    mysql_mutex_lock(&thd->LOCK_thd_kill);
+    do_end_of_statement= thd_is_connection_alive(thd);
+    mysql_mutex_unlock(&thd->LOCK_thd_kill);
   }
   else
     do_end_of_statement= true;
@@ -7737,14 +7733,22 @@ static bool wsrep_mysql_parse(THD *thd, char *rawbuf, uint length,
                   (thd->get_stmt_da()->is_error()) ?
                    thd->get_stmt_da()->sql_errno() : 0);
 
-      thd->killed = NOT_KILLED;
+      thd->reset_kill_query();
       wsrep_override_error(thd, ER_LOCK_DEADLOCK);
     }
 
-    if (wsrep_after_statement(thd) && is_autocommit)
+#ifdef ENABLED_DEBUG_SYNC
+    /* we need the test otherwise we get stuck in the "SET DEBUG_SYNC" itself */
+    if (thd->lex->sql_command != SQLCOM_SET_OPTION)
+      DEBUG_SYNC(thd, "wsrep_after_statement_enter");
+#endif
+
+    if (wsrep_after_statement(thd) &&
+        is_autocommit              &&
+        thd_is_connection_alive(thd))
     {
       thd->reset_for_next_command();
-      thd->killed= NOT_KILLED;
+      thd->reset_kill_query();
       if (is_autocommit                           &&
           thd->lex->sql_command != SQLCOM_SELECT  &&
           thd->wsrep_retry_counter < thd->variables.wsrep_retry_autocommit)
@@ -7774,7 +7778,7 @@ static bool wsrep_mysql_parse(THD *thd, char *rawbuf, uint length,
                     thd->variables.wsrep_retry_autocommit,
                     WSREP_QUERY(thd));
         my_error(ER_LOCK_DEADLOCK, MYF(0));
-        thd->killed= NOT_KILLED;
+        thd->reset_kill_query();
         thd->wsrep_retry_counter= 0;             //  reset
       }
     }
diff --git a/sql/wsrep_high_priority_service.cc b/sql/wsrep_high_priority_service.cc
index 73cdbd1c217..3077985250d 100644
--- a/sql/wsrep_high_priority_service.cc
+++ b/sql/wsrep_high_priority_service.cc
@@ -598,7 +598,7 @@ Wsrep_replayer_service::~Wsrep_replayer_service()
   if (m_replay_status == wsrep::provider::success)
   {
     DBUG_ASSERT(replayer_thd->wsrep_cs().current_error() == wsrep::e_success);
-    orig_thd->killed= NOT_KILLED;
+    orig_thd->reset_kill_query();
     my_ok(orig_thd, m_da_shadow.affected_rows, m_da_shadow.last_insert_id);
   }
   else if (m_replay_status == wsrep::provider::error_certification_failed)