From 72e978828edb6b6cc045e6c728747dafd46b8732 Mon Sep 17 00:00:00 2001
From: Davi Arnaut <Davi.Arnaut@Sun.COM>
Date: Fri, 3 Apr 2009 16:11:54 -0300
Subject: Bug#43230: SELECT ... FOR UPDATE can hang with FLUSH TABLES WITH READ
 LOCK indefinitely

The problem is that a SELECT .. FOR UPDATE statement might open
a table and later wait for a impeding global read lock without
noticing whether it is holding a table that is being waited upon
the the flush phase of the process that took the global read
lock.

The same problem also affected the following statements:

LOCK TABLES .. WRITE
UPDATE .. SET (update and multi-table update)
TRUNCATE TABLE ..
LOAD DATA ..

The solution is to make the above statements wait for a impending
global read lock before opening the tables. If there is no
impending global read lock, the statement raises a temporary
protection against global read locks and progresses smoothly
towards completion.

Important notice: the patch does not try to address all possible
cases, only those which are common and can be fixed unintrusively
enough for 5.0.

mysql-test/r/lock_multi.result:
  Add test case result for Bug#43230
mysql-test/t/lock_multi.test:
  Add test case for Bug#43230
sql/sql_lex.cc:
  Initialize flag.
sql/sql_lex.h:
  Add a flag to the lexer.
sql/sql_parse.cc:
  Wait for the global read lock is a write lock is going to be
  taken. The wait is done before opening tables.
sql/sql_yacc.yy:
  Protect against the GRL if its a SELECT .. FOR UPDATE or LOCK TABLES
  .. WRITE statement.
---
 mysql-test/r/lock_multi.result | 55 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

(limited to 'mysql-test/r/lock_multi.result')

diff --git a/mysql-test/r/lock_multi.result b/mysql-test/r/lock_multi.result
index d1b50a0080c..037b375fe0b 100644
--- a/mysql-test/r/lock_multi.result
+++ b/mysql-test/r/lock_multi.result
@@ -133,3 +133,58 @@ ALTER TABLE t1 ADD COLUMN a INT;
 # 2.2.1. normal mode
 # 2.2.2. PS mode
 DROP TABLE t1;
+create table t1 (a int);
+create table t2 like t1;
+# con1
+lock tables t1 write;
+# con2
+flush tables with read lock;
+# con5
+# global read lock is taken
+# con3
+select * from t2 for update;
+# waiting for release of read lock
+# con4
+# would hang and later cause a deadlock
+flush tables t2;
+# clean up
+unlock tables;
+unlock tables;
+a
+drop table t1,t2;
+#
+# Lightweight version:
+# Ensure that the wait for a GRL is done before opening tables.
+#
+create table t1 (a int);
+create table t2 like t1;
+#
+# UPDATE
+#
+# default
+flush tables with read lock;
+# con1
+update t2 set a = 1;
+# default
+# statement is waiting for release of read lock
+# con2
+flush table t2;
+# default
+unlock tables;
+# con1
+#
+# LOCK TABLES .. WRITE
+#
+# default
+flush tables with read lock;
+# con1
+lock tables t2 write;
+# default
+# statement is waiting for release of read lock
+# con2
+flush table t2;
+# default
+unlock tables;
+# con1
+unlock tables;
+drop table t1,t2;
-- 
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