Backport of:

------------------------------------------------------------
revno: 2617.69.37
committer: Dmitry Lenev <dlenev@mysql.com>
branch nick: mysql-next-bg46748
timestamp: Fri 2009-08-21 18:17:02 +0400
message:
  Fix for bug #46748 "Assertion in MDL_context::wait_for_locks()
  on INSERT + CREATE TRIGGER".

  Concurrent execution of statements involving stored functions or triggers
  which were using several tables and DDL statements which affected those
  tables on debug build of server might have led to assertion failures in
  MDL_context::wait_for_locks(). Non-debug build was not affected.

  The problem was that during back-off which happens when open_tables()
  encounters conflicting metadata lock for one of the tables being open
  we didn't reset MDL_request::ticket value for requests which correspond
  to tables from extended prelocking set. Since these requests are part
  of of list of requests to be waited for in Open_table_context this broke
  assumption that ticket value for them is 0 in MDL_context::wait_for_locks()
  and caused assertion failure.

  This fix ensures that close_tables_for_reopen(), which performs this back-off
  resets MDL_request::ticket value not only for tables directly used by the
  statement but also for tables from extended prelocking set, thus satisfying
  assumption described above.

mysql-test/r/mdl_sync.result

@@ -19,3 +19,46 @@ connection: con2
 ERROR 42S02: Unknown table 't1'
 drop table t3;
 SET DEBUG_SYNC= 'RESET';
+#
+# Test for bug #46748 "Assertion in MDL_context::wait_for_locks()
+# on INSERT + CREATE TRIGGER".
+#
+drop tables if exists t1, t2, t3, t4, t5;
+# Let us simulate scenario in which we open some tables from extended
+# part of prelocking set but then encounter conflicting metadata lock,
+# so have to back-off and wait for it to go away.
+create table t1 (i int);
+create table t2 (j int);
+create table t3 (k int);
+create table t4 (l int);
+create trigger t1_bi before insert on t1 for each row
+insert into t2 values (new.i);
+create trigger t2_bi before insert on t2 for each row
+insert into t3 values (new.j);
+#
+# Switching to connection 'con1root'.
+lock tables t4 read;
+#
+# Switching to connection 'con2root'.
+# Send :
+rename table t3 to t5, t4 to t3;;
+#
+# Switching to connection 'default'.
+# Wait until the above RENAME TABLE adds pending requests for exclusive
+# metadata lock on its tables and blocks due to 't4' being used by LOCK
+# TABLES.
+# Send :
+insert into t1 values (1);;
+#
+# Switching to connection 'con1root'.
+# Wait until INSERT statement waits due to encountering pending
+# exclusive metadata lock on 't3'.
+unlock tables;
+#
+# Switching to connection 'con2root'.
+# Reap RENAME TABLE.
+#
+# Switching to connection 'default'.
+# Reap INSERT.
+# Clean-up.
+drop tables t1, t2, t3, t5;

mysql-test/t/mdl_sync.test

@@ -3,6 +3,10 @@
 #
 --source include/have_debug_sync.inc
 
+# Save the initial number of concurrent sessions.
+--source include/count_sessions.inc
+
+
 # Clean up resources used in this test case.
 --disable_warnings
 SET DEBUG_SYNC= 'RESET';
@@ -67,3 +71,76 @@ disconnect con3;
 --disable_warnings
 SET DEBUG_SYNC= 'RESET';
 --enable_warnings
+
+
+--echo #
+--echo # Test for bug #46748 "Assertion in MDL_context::wait_for_locks()
+--echo # on INSERT + CREATE TRIGGER".
+--echo #
+--disable_warnings
+drop tables if exists t1, t2, t3, t4, t5;
+--enable_warnings
+--echo # Let us simulate scenario in which we open some tables from extended
+--echo # part of prelocking set but then encounter conflicting metadata lock,
+--echo # so have to back-off and wait for it to go away.
+connect (con1root,localhost,root,,test,,);
+connect (con2root,localhost,root,,test,,);
+connection default;
+create table t1 (i int);
+create table t2 (j int);
+create table t3 (k int);
+create table t4 (l int);
+create trigger t1_bi before insert on t1 for each row
+  insert into t2 values (new.i);
+create trigger t2_bi before insert on t2 for each row
+  insert into t3 values (new.j);
+--echo #
+--echo # Switching to connection 'con1root'.
+connection con1root;
+lock tables t4 read;
+--echo #
+--echo # Switching to connection 'con2root'.
+connection con2root;
+--echo # Send :
+--send rename table t3 to t5, t4 to t3;
+--echo #
+--echo # Switching to connection 'default'.
+connection default;
+--echo # Wait until the above RENAME TABLE adds pending requests for exclusive
+--echo # metadata lock on its tables and blocks due to 't4' being used by LOCK
+--echo # TABLES.
+let $wait_condition= select count(*)= 1 from information_schema.processlist
+                       where state= 'Waiting for table' and
+                             info='rename table t3 to t5, t4 to t3';
+--source include/wait_condition.inc
+--echo # Send :
+--send insert into t1 values (1);
+--echo #
+--echo # Switching to connection 'con1root'.
+connection con1root;
+--echo # Wait until INSERT statement waits due to encountering pending
+--echo # exclusive metadata lock on 't3'.
+let $wait_condition= select count(*)= 1 from information_schema.processlist
+                       where state= 'Waiting for table' and
+                             info='insert into t1 values (1)';
+--source include/wait_condition.inc
+unlock tables;
+--echo #
+--echo # Switching to connection 'con2root'.
+connection con2root;
+--echo # Reap RENAME TABLE.
+--reap
+--echo #
+--echo # Switching to connection 'default'.
+connection default;
+--echo # Reap INSERT.
+--reap
+--echo # Clean-up.
+disconnect con1root;
+disconnect con2root;
+drop tables t1, t2, t3, t5;
+
+
+# Check that all connections opened by test cases in this file are really
+# gone so execution of other tests won't be affected by their presence.
+--source include/wait_until_count_sessions.inc

sql/sql_base.cc

@@ -5104,19 +5104,31 @@ bool lock_tables(THD *thd, TABLE_LIST *tables, uint count,
 
 void close_tables_for_reopen(THD *thd, TABLE_LIST **tables)
 {
+  TABLE_LIST *first_not_own_table= thd->lex->first_not_own_table();
+  TABLE_LIST *tmp;
+
   /*
     If table list consists only from tables from prelocking set, table list
     for new attempt should be empty, so we have to update list's root pointer.
   */
-  if (thd->lex->first_not_own_table() == *tables)
+  if (first_not_own_table == *tables)
     *tables= 0;
   thd->lex->chop_off_not_own_tables();
   sp_remove_not_own_routines(thd->lex);
-  for (TABLE_LIST *tmp= *tables; tmp; tmp= tmp->next_global)
+  for (tmp= *tables; tmp; tmp= tmp->next_global)
   {
     tmp->table= 0;
     tmp->mdl_request.ticket= NULL;
   }
+  /*
+    Metadata lock requests for tables from extended part of prelocking set
+    are part of list of requests to be waited for in Open_table_context.
+    So to satisfy assumptions in MDL_context::wait_for_locks(), which will
+    performs the waiting, we have to reset MDL_request::ticket values for
+    them as well.
+  */
+  for (tmp= first_not_own_table; tmp; tmp= tmp->next_global)
+    tmp->mdl_request.ticket= NULL;
   close_thread_tables(thd);
   if (!thd->locked_tables_mode)
     thd->mdl_context.release_all_locks();