From 98c4476b49b19a289ec61a645a22deea8c4ef8ee Mon Sep 17 00:00:00 2001
From: Konstantin Osipov <kostja@sun.com>
Date: Fri, 20 Nov 2009 23:12:57 +0300
Subject: [PATCH] Backport of:
 ------------------------------------------------------------ revno:
 2476.1116.1 committer: davi@mysql.com/endora.local timestamp: Fri 2007-12-14
 10:10:19 -0200 message: DROP TABLE under LOCK TABLES simultaneous to a FLUSH
 TABLES WITH READ LOCK (global read lock) can lead to a deadlock.

The solution is to not wait for the global read lock if the
thread is holding any locked tables.

Related to bugs 23713 and 32395. This issues is being fixed
only on 6.0 because it depends on the fix for bug 25858 --
which was fixed only on 6.0.
---
 mysql-test/r/lock_multi.result |  9 +++++++++
 mysql-test/t/lock_multi.test   | 37 +++++++++++++++++++++++++++++++++-
 sql/sql_table.cc               | 15 ++++++--------
 3 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/mysql-test/r/lock_multi.result b/mysql-test/r/lock_multi.result
index 49e51631b91..3f1165fd069 100644
--- a/mysql-test/r/lock_multi.result
+++ b/mysql-test/r/lock_multi.result
@@ -210,3 +210,12 @@ select @tlwa < @tlwb;
 @tlwa < @tlwb
 1
 End of 5.1 tests
+drop table if exists t1;
+create table t1 (i int);
+connection: default
+lock tables t1 write;
+connection: flush
+flush tables with read lock;;
+connection: default
+flush tables;
+drop table t1;
diff --git a/mysql-test/t/lock_multi.test b/mysql-test/t/lock_multi.test
index cd4d70bd99e..75ee6d07723 100644
--- a/mysql-test/t/lock_multi.test
+++ b/mysql-test/t/lock_multi.test
@@ -636,6 +636,41 @@ select @tlwa < @tlwb;
 
 --echo End of 5.1 tests
 
+#
+# Test that DROP TABLES does not wait for a impending FLUSH TABLES
+# WITH READ LOCK
+#
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+create table t1 (i int);
+connect (flush,localhost,root,,test,,);
+connection default;
+--echo connection: default
+lock tables t1 write;
+connection flush;
+--echo connection: flush
+--send flush tables with read lock;
+connection default;
+--echo connection: default
+let $wait_condition=
+  select count(*) = 1 from information_schema.processlist
+  where state = "Flushing tables";
+--source include/wait_condition.inc
+flush tables;
+let $wait_condition=
+  select count(*) = 1 from information_schema.processlist
+  where state = "Flushing tables";
+--source include/wait_condition.inc
+drop table t1;
+let $wait_condition=
+  select count(*) = 0 from information_schema.processlist
+  where state = "Flushing tables";
+--source include/wait_condition.inc
+connection flush;
+--reap
+connection default;
+disconnect flush;
 # Wait till all disconnects are completed
 --source include/wait_until_count_sessions.inc
-
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 63dc4e68fdf..150a896103c 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -1766,7 +1766,8 @@ void write_bin_log(THD *thd, bool clear_error,
     If a table is in use, we will wait for all users to free the table
     before dropping it
 
-    Wait if global_read_lock (FLUSH TABLES WITH READ LOCK) is set.
+    Wait if global_read_lock (FLUSH TABLES WITH READ LOCK) is set, but
+    not if under LOCK TABLES.
 
   RETURN
     FALSE OK.  In this case ok packet is sent to user
@@ -1777,7 +1778,7 @@ void write_bin_log(THD *thd, bool clear_error,
 bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
                     my_bool drop_temporary)
 {
-  bool error= FALSE, need_start_waiters= FALSE;
+  bool error= FALSE, need_start_waiting= FALSE;
   Drop_table_error_handler err_handler(thd->get_internal_handler());
   DBUG_ENTER("mysql_rm_table");
 
@@ -1785,13 +1786,9 @@ bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
 
   if (!drop_temporary)
   {
-    if ((error= wait_if_global_read_lock(thd, 0, 1)))
-    {
-      my_error(ER_TABLE_NOT_LOCKED_FOR_WRITE, MYF(0), tables->table_name);
+    if (!thd->locked_tables &&
+        !(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
       DBUG_RETURN(TRUE);
-    }
-    else
-      need_start_waiters= TRUE;
   }
 
   /*
@@ -1804,7 +1801,7 @@ bool mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists,
   thd->pop_internal_handler();
 
 
-  if (need_start_waiters)
+  if (need_start_waiting)
     start_waiting_global_read_lock(thd);
 
   if (error)