branches/zip: Fix a race condition caused by

SET GLOBAL innodb_commit_concurrency=DEFAULT. (Bug #45749)
When innodb_commit_concurrency is initially set nonzero,
DEFAULT would change it back to 0, triggering Bug #42101.
rb://139 approved by Heikki Tuuri.

ChangeLog

+2009-06-25	The InnoDB Team
+
+	* handler/ha_innodb.cc,
+	mysql-test/innodb_bug42101.test,
+	mysql-test/innodb_bug42101.result,
+	mysql-test/innodb_bug42101-nonzero.test,
+	mysql-test/innodb_bug42101-nonzero.result:
+	Fix Bug#45749 Race condition in SET GLOBAL
+	innodb_commit_concurrency=DEFAULT
+
 2009-06-25	The InnoDB Team
 
 	* dict/dict0dict.c:

handler/ha_innodb.cc

@@ -228,6 +228,20 @@ static handler *innobase_create_handler(handlerton *hton,
                                         TABLE_SHARE *table,
                                         MEM_ROOT *mem_root);
 
+/** @brief Initialize the default value of innodb_commit_concurrency.
+
+Once InnoDB is running, the innodb_commit_concurrency must not change
+from zero to nonzero. (Bug #42101)
+
+The initial default value is 0, and without this extra initialization,
+SET GLOBAL innodb_commit_concurrency=DEFAULT would set the parameter
+to 0, even if it was initially set to nonzero at the command line
+or configuration file. */
+static
+void
+innobase_commit_concurrency_init_default(void);
+/*==========================================*/
+
 /************************************************************//**
 Validate the file format name and return its corresponding id.
 @return	valid file format id */
@@ -2196,6 +2210,8 @@ innobase_change_buffering_inited_ok:
 	ut_a(0 == strcmp(my_charset_latin1.name, "latin1_swedish_ci"));
 	srv_latin1_ordering = my_charset_latin1.sort_order;
 
+	innobase_commit_concurrency_init_default();
+
 	/* Since we in this module access directly the fields of a trx
 	struct, and due to different headers and flags it might happen that
 	mutex_t has a different size in this module and in InnoDB
@@ -9887,6 +9903,24 @@ i_s_innodb_cmpmem,
 i_s_innodb_cmpmem_reset
 mysql_declare_plugin_end;
 
+/** @brief Initialize the default value of innodb_commit_concurrency.
+
+Once InnoDB is running, the innodb_commit_concurrency must not change
+from zero to nonzero. (Bug #42101)
+
+The initial default value is 0, and without this extra initialization,
+SET GLOBAL innodb_commit_concurrency=DEFAULT would set the parameter
+to 0, even if it was initially set to nonzero at the command line
+or configuration file. */
+static
+void
+innobase_commit_concurrency_init_default(void)
+/*==========================================*/
+{
+	MYSQL_SYSVAR_NAME(commit_concurrency).def_val
+		= innobase_commit_concurrency;
+}
+
 #ifdef UNIV_COMPILE_TEST_FUNCS
 
 typedef struct innobase_convert_name_test_struct {

mysql-test/innodb_bug42101-nonzero.result

@@ -11,11 +11,15 @@ set global innodb_commit_concurrency=42;
 select @@innodb_commit_concurrency;
 @@innodb_commit_concurrency
 42
+set global innodb_commit_concurrency=DEFAULT;
+select @@innodb_commit_concurrency;
+@@innodb_commit_concurrency
+1
 set global innodb_commit_concurrency=0;
 ERROR HY000: Incorrect arguments to SET
 select @@innodb_commit_concurrency;
 @@innodb_commit_concurrency
-42
+1
 set global innodb_commit_concurrency=1;
 select @@innodb_commit_concurrency;
 @@innodb_commit_concurrency

mysql-test/innodb_bug42101-nonzero.test

@@ -12,6 +12,8 @@ set global innodb_commit_concurrency=1;
 select @@innodb_commit_concurrency;
 set global innodb_commit_concurrency=42;
 select @@innodb_commit_concurrency;
+set global innodb_commit_concurrency=DEFAULT;
+select @@innodb_commit_concurrency;
 --error ER_WRONG_ARGUMENTS
 set global innodb_commit_concurrency=0;
 select @@innodb_commit_concurrency;

mysql-test/innodb_bug42101.result

@@ -16,3 +16,7 @@ set global innodb_commit_concurrency=0;
 select @@innodb_commit_concurrency;
 @@innodb_commit_concurrency
 0
+set global innodb_commit_concurrency=DEFAULT;
+select @@innodb_commit_concurrency;
+@@innodb_commit_concurrency
+0

mysql-test/innodb_bug42101.test

@@ -15,3 +15,5 @@ set global innodb_commit_concurrency=42;
 select @@innodb_commit_concurrency;
 set global innodb_commit_concurrency=0;
 select @@innodb_commit_concurrency;
+set global innodb_commit_concurrency=DEFAULT;
+select @@innodb_commit_concurrency;