Applying InnoDB snapshot 5.1-ss5488,part 2. Fixes BUG#45749

BUG#45749 - Race condition in SET GLOBAL innodb_commit_concurrency=DEFAULT

Detailed revision comments:

r5419 | marko | 2009-06-25 16:11:57 +0300 (Thu, 25 Jun 2009) | 18 lines
branches/5.1: Merge r5418 from branches/zip:

  ------------------------------------------------------------------------
  r5418 | marko | 2009-06-25 15:55:52 +0300 (Thu, 25 Jun 2009) | 5 lines
  Changed paths:
     M /branches/zip/ChangeLog
     M /branches/zip/handler/ha_innodb.cc
     M /branches/zip/mysql-test/innodb_bug42101-nonzero.result
     M /branches/zip/mysql-test/innodb_bug42101-nonzero.test
     M /branches/zip/mysql-test/innodb_bug42101.result
     M /branches/zip/mysql-test/innodb_bug42101.test
  
  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.
  ------------------------------------------------------------------------

mysql-test/r/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/r/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/t/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/t/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;

storage/innobase/handler/ha_innodb.cc

@@ -166,6 +166,20 @@ static handler *innobase_create_handler(handlerton *hton,
 
 static const char innobase_hton_name[]= "InnoDB";
 
+/** @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);
+/*==========================================*/
+
 /*****************************************************************
 Check for a valid value of innobase_commit_concurrency. */
 static
@@ -1775,6 +1789,8 @@ innobase_init(
 						(char*)"latin1_swedish_ci"));
 	memcpy(srv_latin1_ordering, my_charset_latin1.sort_order, 256);
 
+	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
@@ -8464,3 +8480,21 @@ mysql_declare_plugin(innobase)
   NULL /* reserved */
 }
 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;
+}