Parallel replication async deadlock kill

When a deadlock kill is detected inside the storage engine, the kill
is not done immediately, to avoid calling back into the storage engine
kill_query method with various lock subsystem mutexes held. Instead the
kill is queued and done later by a slave background thread.

This patch in preparation for fixing TokuDB optimistic parallel
replication, as well as for removing locking hacks in InnoDB/XtraDB in
10.2.

Signed-off-by: Kristian Nielsen <knielsen at knielsen-hq.org>

1 files changed, 26 insertions, 4 deletions

diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index f2437a6953b..761471fc1cb 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -107,6 +107,25 @@ handle_queued_pos_update(THD *thd, rpl_parallel_thread::queued_event *qev)
 }
 
 
+/*
+  Wait for any pending deadlock kills. Since deadlock kills happen
+  asynchronously, we need to be sure they will be completed before starting a
+  new transaction. Otherwise the new transaction might suffer a spurious kill.
+*/
+static void
+wait_for_pending_deadlock_kill(THD *thd, rpl_group_info *rgi)
+{
+  PSI_stage_info old_stage;
+
+  mysql_mutex_lock(&thd->LOCK_wakeup_ready);
+  thd->ENTER_COND(&thd->COND_wakeup_ready, &thd->LOCK_wakeup_ready,
+                  &stage_waiting_for_deadlock_kill, &old_stage);
+  while (rgi->killed_for_retry == rpl_group_info::RETRY_KILL_PENDING)
+    mysql_cond_wait(&thd->COND_wakeup_ready, &thd->LOCK_wakeup_ready);
+  thd->EXIT_COND(&old_stage);
+}
+
+
 static void
 finish_event_group(rpl_parallel_thread *rpt, uint64 sub_id,
                    rpl_parallel_entry *entry, rpl_group_info *rgi)
@@ -212,6 +231,8 @@ finish_event_group(rpl_parallel_thread *rpt, uint64 sub_id,
     entry->stop_on_error_sub_id= sub_id;
   mysql_mutex_unlock(&entry->LOCK_parallel_entry);
 
+  if (rgi->killed_for_retry == rpl_group_info::RETRY_KILL_PENDING)
+    wait_for_pending_deadlock_kill(thd, rgi);
   thd->clear_error();
   thd->reset_killed();
   /*
@@ -604,7 +625,6 @@ convert_kill_to_deadlock_error(rpl_group_info *rgi)
   {
     thd->clear_error();
     my_error(ER_LOCK_DEADLOCK, MYF(0));
-    rgi->killed_for_retry= false;
     thd->reset_killed();
   }
 }
@@ -695,14 +715,16 @@ do_retry:
     thd->wait_for_commit_ptr->unregister_wait_for_prior_commit();
   DBUG_EXECUTE_IF("inject_mdev8031", {
       /* Simulate that we get deadlock killed at this exact point. */
-      rgi->killed_for_retry= true;
+      rgi->killed_for_retry= rpl_group_info::RETRY_KILL_KILLED;
       mysql_mutex_lock(&thd->LOCK_thd_data);
       thd->killed= KILL_CONNECTION;
       mysql_mutex_unlock(&thd->LOCK_thd_data);
   });
   rgi->cleanup_context(thd, 1);
+  wait_for_pending_deadlock_kill(thd, rgi);
   thd->reset_killed();
   thd->clear_error();
+  rgi->killed_for_retry = rpl_group_info::RETRY_KILL_NONE;
 
   /*
     If we retry due to a deadlock kill that occurred during the commit step, we
@@ -841,7 +863,7 @@ do_retry:
           {
             /* Simulate that we get deadlock killed during open_binlog(). */
             thd->reset_for_next_command();
-            rgi->killed_for_retry= true;
+            rgi->killed_for_retry= rpl_group_info::RETRY_KILL_KILLED;
             mysql_mutex_lock(&thd->LOCK_thd_data);
             thd->killed= KILL_CONNECTION;
             mysql_mutex_unlock(&thd->LOCK_thd_data);
@@ -1741,7 +1763,7 @@ rpl_parallel_thread::get_rgi(Relay_log_info *rli, Gtid_log_event *gtid_ev,
   rgi->relay_log= rli->last_inuse_relaylog;
   rgi->retry_start_offset= rli->future_event_relay_log_pos-event_size;
   rgi->retry_event_count= 0;
-  rgi->killed_for_retry= false;
+  rgi->killed_for_retry= rpl_group_info::RETRY_KILL_NONE;
 
   return rgi;
 }