Bug#40536: SELECT is blocked by INSERT DELAYED waiting on

           upgrading lock, even with low_priority_updates

The problem is that there is no mechanism to control whether a
delayed insert takes a high or low priority lock on a table.

The solution is to modify the delayed insert thread ("handler")
to take into account the global value of low_priority_updates
when taking table locks. The value of low_priority_updates is
retrieved when the insert delayed thread is created and will
remain the same for the duration of the thread.


include/thr_lock.h:
  Update prototype.
mysql-test/r/delayed.result:
  Add test case result for Bug#40536
mysql-test/t/delayed.test:
  Add test case for Bug#40536
mysys/thr_lock.c:
  Add function parameter which specifies the write lock type.
sql/sql_insert.cc:
  Take a low priority write lock if global value of low_priority_updates
  was ON when the thread was created.

1 files changed, 2 insertions, 1 deletions

diff --git a/include/thr_lock.h b/include/thr_lock.h
index c7754ada299..e409df30972 100644
--- a/include/thr_lock.h
+++ b/include/thr_lock.h
@@ -159,7 +159,8 @@ void thr_multi_unlock(THR_LOCK_DATA **data,uint count);
 void thr_abort_locks(THR_LOCK *lock, my_bool upgrade_lock);
 my_bool thr_abort_locks_for_thread(THR_LOCK *lock, my_thread_id thread);
 void thr_print_locks(void);		/* For debugging */
-my_bool thr_upgrade_write_delay_lock(THR_LOCK_DATA *data);
+my_bool thr_upgrade_write_delay_lock(THR_LOCK_DATA *data,
+                                     enum thr_lock_type new_lock_type);
 void    thr_downgrade_write_lock(THR_LOCK_DATA *data,
                                  enum thr_lock_type new_lock_type);
 my_bool thr_reschedule_write_lock(THR_LOCK_DATA *data);