commit af11f212173e6d92629aaface66982c5a776d78e
Author: Sachin <sachinsetia1001@gmail.com>
Date:   Thu Jul 16 14:24:30 2020 +0530

    MDEV-23089 rpl_parallel2 fails in 10.5
   
    Problem:- rpl_parallel2 was failing non-deterministically
   
    Analysis:-
      So when we issue FTWRL. Worker thread will be waiting in do_ftwrl_wait().
      Then from other connection we issue STOP SLAVE , which turn force_abort = 1
      So we exit out of loop in do_fterl_wait(). Then we get deadlock further down
      the execution path.
    Solution:-
      We will assign 1 to skip_event_group when we are aborted in do_ftwrl_wait.
      And rpl_parallel_entry->pause_sub-id is only reset when force_abort is off
      in rpl_pause_after_ftwrl

diff --git a/mysql-test/suite/rpl/disabled.def b/mysql-test/suite/rpl/disabled.def
index 640c4b56cd0..9e52c277726 100644
--- a/mysql-test/suite/rpl/disabled.def
+++ b/mysql-test/suite/rpl/disabled.def
@@ -19,4 +19,3 @@ rpl_semi_sync_after_sync  : fails after MDEV-16172
 rpl_slave_grp_exec: MDEV-10514
 rpl_auto_increment_update_failure  : disabled for now
 rpl_current_user          : waits for MDEV-22374 fix
-rpl_parallel2             : waits for MDEV-23089
diff --git a/sql/rpl_parallel.cc b/sql/rpl_parallel.cc
index 94882230682..63e0c6bfc20 100644
--- a/sql/rpl_parallel.cc
+++ b/sql/rpl_parallel.cc
@@ -396,13 +396,14 @@ do_gco_wait(rpl_group_info *rgi, group_commit_orderer *gco,
 }
 
 
-static void
+static bool
 do_ftwrl_wait(rpl_group_info *rgi,
               bool *did_enter_cond, PSI_stage_info *old_stage)
 {
   THD *thd= rgi->thd;
   rpl_parallel_entry *entry= rgi->parallel_entry;
   uint64 sub_id= rgi->gtid_sub_id;
+  bool aborted= false;
   DBUG_ENTER("do_ftwrl_wait");
 
   mysql_mutex_assert_owner(&entry->LOCK_parallel_entry);
@@ -425,7 +426,10 @@ do_ftwrl_wait(rpl_group_info *rgi,
     do
     {
       if (entry->force_abort || rgi->worker_error)
+      {
+        aborted= true;
         break;
+      }
       if (unlikely(thd->check_killed()))
       {
         slave_output_error_info(rgi, thd);
@@ -444,7 +448,7 @@ do_ftwrl_wait(rpl_group_info *rgi,
   if (sub_id > entry->largest_started_sub_id)
     entry->largest_started_sub_id= sub_id;
 
-  DBUG_VOID_RETURN;
+  DBUG_RETURN(aborted);
 }
 
 
@@ -530,7 +534,18 @@ rpl_unpause_after_ftwrl(THD *thd)
     mysql_mutex_lock(&e->LOCK_parallel_entry);
     rpt->pause_for_ftwrl = false;
     mysql_mutex_unlock(&rpt->LOCK_rpl_thread);
-    e->pause_sub_id= (uint64)ULONGLONG_MAX;
+    /*
+     * Dont change pause_sub_id if force_abort is on
+     * Reason:- This will make skip_event_group one while calling
+     * do_ftwrl_wait which will make worker to execute transaction in the
+     * queue. And will create gaps, Transaction between setting of pause_sub_id
+     * and unsetting wont be applied on slave. So if there is force_abort
+     * we wont change the pause_sub_id.
+     * We are not changing pause_for_ftwrl because we want worker to exit in
+     * event of STOP SLAVE otherwise it will hang forever
+    */
+    if (!e->force_abort)
+      e->pause_sub_id= (uint64)ULONGLONG_MAX;
     mysql_cond_broadcast(&e->COND_parallel_entry);
     mysql_mutex_unlock(&e->LOCK_parallel_entry);
   }
@@ -1224,7 +1239,7 @@ handle_rpl_parallel_thread(void *arg)
           rgi->worker_error= 1;
         }
         if (likely(!skip_event_group))
-          do_ftwrl_wait(rgi, &did_enter_cond, &old_stage);
+          skip_event_group= do_ftwrl_wait(rgi, &did_enter_cond, &old_stage);
 
         /*
           Register ourself to wait for the previous commit, if we need to do
--