Applying patch from SergeyV

Fixes bug#17264, for alter table on win32 for successfull operation completion
it is used TL_WRITE(=10) lock instead of TL_WRITE_ALLOW_READ(=6), however here
in innodb handler TL_WRTIE is lifted to TL_WRITE_ALLOW_WRITE, which causes
race condition when several clients do alter table simultaneously.

mysql-test/r/lock_multi.result

@@ -67,3 +67,9 @@ Select_priv
 N
 use test;
 use test;
+create table t1 (f1 int(12) unsigned not null auto_increment, primary key(f1)) engine=innodb;
+lock tables t1 write;
+ alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; //
+ alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; //
+unlock tables;
+drop table t1;

mysql-test/t/lock_multi.test

@@ -171,4 +171,30 @@ use test;
 #
 connection default;
 
+#
+# Bug #17264: MySQL Server freeze
+#
+connection locker;
+create table t1 (f1 int(12) unsigned not null auto_increment, primary key(f1)) engine=innodb;
+lock tables t1 write;
+connection writer;
+--sleep 2
+delimiter //;
+send alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; //
+delimiter ;//
+connection reader;
+--sleep 2
+delimiter //;
+send alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; //
+delimiter ;//
+connection locker;
+--sleep 2
+unlock tables;
+connection writer;
+reap;
+connection reader;
+reap;
+connection locker;
+drop table t1;
+
 # End of 5.0 tests

sql/ha_innodb.cc

@@ -6684,6 +6684,17 @@ ha_innobase::store_lock(
 		    && !thd->tablespace_op
 		    && thd->lex->sql_command != SQLCOM_TRUNCATE
 		    && thd->lex->sql_command != SQLCOM_OPTIMIZE
+#ifdef __WIN__
+                /* 
+                   for alter table on win32 for succesfull operation 
+                   completion it is used TL_WRITE(=10) lock instead of
+                   TL_WRITE_ALLOW_READ(=6), however here in innodb handler
+                   TL_WRITE is lifted to TL_WRITE_ALLOW_WRITE, which causes
+                   race condition when several clients do alter table 
+                   simultaneously (bug #17264). This fix avoids the problem.
+                */
+                    && thd->lex->sql_command != SQLCOM_ALTER_TABLE
+#endif
 		    && thd->lex->sql_command != SQLCOM_CREATE_TABLE) {
 
 			lock_type = TL_WRITE_ALLOW_WRITE;