Fix for MDEV-4009: main.delayed sporadically fails with "query 'REPLACE DELAYED t1 VALUES (5)' failed: 1317: Query execution was interrupted"

- Fixed broadcast without a proper mutex
- Don't break existing locks if we are just testing if we can get the lock

mysql-test/r/create_delayed.result:
  Added test case for failures with INSERT DELAYED with CREATE and DROP TABLE
mysql-test/t/create_delayed.test:
  Added test case for failures with INSERT DELAYED with CREATE and DROP TABLE
sql/mdl.cc:
  Don't break existing locks for timeout=0 (ie, just check if there are conflicting locks).
  This fixed the bug that INSERT DELAYED didn't work properly with CREATE TABLE
sql/sql_base.cc:
  One neads to hold the mutex before doing a mysql_cond_broadcast()
  This fixed the bug that INSERT DELAYED didn't work properly with DROP TABLE
sql/sql_insert.cc:
  Protect setting of mysys_var->current_mutex.

1 files changed, 5 insertions, 1 deletions

diff --git a/sql/mdl.cc b/sql/mdl.cc
index 5e297051377..a2113909116 100644
--- a/sql/mdl.cc
+++ b/sql/mdl.cc
@@ -2078,7 +2078,11 @@ MDL_context::acquire_lock(MDL_request *mdl_request, ulong lock_wait_timeout)
   */
   m_wait.reset_status();
 
-  if (lock->needs_notification(ticket))
+  /*
+    Don't break conflicting locks if timeout is 0 as 0 is used
+    To check if there is any conflicting locks...
+  */
+  if (lock->needs_notification(ticket) && lock_wait_timeout)
     lock->notify_conflicting_locks(this);
 
   mysql_prlock_unlock(&lock->m_rwlock);