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.

1 files changed, 128 insertions, 0 deletions

diff --git a/mysql-test/t/lock_multi.test b/mysql-test/t/lock_multi.test
index 6c3c942b046..fa6af85f29c 100644
--- a/mysql-test/t/lock_multi.test
+++ b/mysql-test/t/lock_multi.test
@@ -683,6 +683,134 @@ DROP TABLE t1;
 --disconnect locker
 --disconnect writer
 
+#
+# Bug#43230: SELECT ... FOR UPDATE can hang with FLUSH TABLES WITH READ LOCK indefinitely
+#
+
+connect (con1,localhost,root,,);
+connect (con2,localhost,root,,);
+connect (con3,localhost,root,,);
+connect (con4,localhost,root,,);
+connect (con5,localhost,root,,);
+
+create table t1 (a int);
+create table t2 like t1;
+
+connection con1;
+--echo # con1
+lock tables t1 write;
+connection con2;
+--echo # con2
+send flush tables with read lock;
+connection con5;
+--echo # con5
+let $show_statement= SHOW PROCESSLIST;
+let $field= State;
+let $condition= = 'Flushing tables';
+--source include/wait_show_condition.inc
+--echo # global read lock is taken
+connection con3;
+--echo # con3
+send select * from t2 for update;
+connection con5;
+let $show_statement= SHOW PROCESSLIST;
+let $field= State;
+let $condition= = 'Waiting for release of readlock';
+--source include/wait_show_condition.inc
+--echo # waiting for release of read lock
+connection con4;
+--echo # con4
+--echo # would hang and later cause a deadlock
+flush tables t2;
+connection con1;
+--echo # clean up
+unlock tables;
+connection con2;
+--reap
+unlock tables;
+connection con3;
+--reap
+connection default;
+disconnect con5;
+disconnect con4;
+disconnect con3;
+disconnect con2;
+disconnect con1;
+
+drop table t1,t2;
+
+--echo #
+--echo # Lightweight version:
+--echo # Ensure that the wait for a GRL is done before opening tables.
+--echo #
+
+connect (con1,localhost,root,,);
+connect (con2,localhost,root,,);
+
+create table t1 (a int);
+create table t2 like t1;
+
+--echo #
+--echo # UPDATE
+--echo #
+
+connection default;
+--echo # default
+flush tables with read lock;
+connection con1;
+--echo # con1
+send update t2 set a = 1;
+connection default;
+--echo # default
+let $show_statement= SHOW PROCESSLIST;
+let $field= State;
+let $condition= = 'Waiting for release of readlock';
+--source include/wait_show_condition.inc
+--echo # statement is waiting for release of read lock
+connection con2;
+--echo # con2
+flush table t2;
+connection default;
+--echo # default
+unlock tables;
+connection con1;
+--echo # con1
+--reap
+
+--echo #
+--echo # LOCK TABLES .. WRITE
+--echo #
+
+connection default;
+--echo # default
+flush tables with read lock;
+connection con1;
+--echo # con1
+send lock tables t2 write;
+connection default;
+--echo # default
+let $show_statement= SHOW PROCESSLIST;
+let $field= State;
+let $condition= = 'Waiting for release of readlock';
+--source include/wait_show_condition.inc
+--echo # statement is waiting for release of read lock
+connection con2;
+--echo # con2
+flush table t2;
+connection default;
+--echo # default
+unlock tables;
+connection con1;
+--echo # con1
+--reap
+unlock tables;
+
+connection default;
+disconnect con2;
+disconnect con1;
+
+drop table t1,t2;
+
 # End of 5.0 tests
 
 # Wait till all disconnects are completed