#At file:///home/svoj/mysql/server/mysql-5.5-bugfixing-bug54989/ based on revid:alik@stripped
3186 Sergey Vojtovich 2010-08-20
BUG#54989 - With null_audit installed, server hangs on an
attempt to install a plugin twice
Server crashes when [UN]INSTALL PLUGIN fails (returns an
error) and general log is disabled and there are audit
plugins interested in MYSQL_AUDIT_GENERAL_CLASS.
When audit event is triggered, audit subsystem acquires interested
plugins by walking through plugin list. Evidently plugin list
iterator protects plugin list by acquiring LOCK_plugin, see
plugin_foreach_with_mask().
On the other hand [UN]INSTALL PLUGIN is acquiring LOCK_plugin
rather for a long time.
When audit event is triggered during [UN]INSTALL PLUGIN, plugin
list iterator acquires the same lock (within the same thread)
second time.
Repeatable only with general_log disabled, because general_log
triggers MYSQL_AUDIT_GENERAL_LOG event, which acquires audit
plugins before [UN]INSTALL PLUGIN acquired LOCK_plugin.
With this fix we pre-acquire audit plugins for events that
may potentially occur during [UN]INSTALL PLUGIN.
This hack should be removed when LOCK_plugin is fixed so it
protects only what it supposed to protect.
No test case for this fix - we do not have facility to test
audit plugins yet.
@ sql/sql_audit.cc
Move "acquire audit plugin" logics to a separate
function.
@ sql/sql_audit.h
Move "acquire audit plugin" logics to a separate
function.
@ sql/sql_plugin.cc
Pre-acquire audit plugins for events that may potentially occur
during [UN]INSTALL PLUGIN.
modified:
sql/sql_audit.cc
sql/sql_audit.h
sql/sql_plugin.cc
=== modified file 'sql/sql_audit.cc'
--- a/sql/sql_audit.cc 2010-04-15 09:36:36 +0000
+++ b/sql/sql_audit.cc 2010-08-20 09:58:28 +0000
@@ -138,6 +138,30 @@ static my_bool acquire_plugins(THD *thd,
/**
+ @brief Acquire audit plugins
+
+ @param[in] thd MySQL thread handle
+ @param[in] event_class Audit event class
+
+ @details Ensure that audit plugins interested in given event
+ class are locked by current thread.
+*/
+void mysql_audit_acquire_plugins(THD *thd, uint event_class)
+{
+ unsigned long event_class_mask[MYSQL_AUDIT_CLASS_MASK_SIZE];
+ DBUG_ENTER("mysql_audit_acquire_plugins");
+ set_audit_mask(event_class_mask, event_class);
+ if (thd && !check_audit_mask(mysql_global_audit_mask, event_class_mask) &&
+ check_audit_mask(thd->audit_class_mask, event_class_mask))
+ {
+ plugin_foreach(thd, acquire_plugins, MYSQL_AUDIT_PLUGIN, &event_class);
+ add_audit_mask(thd->audit_class_mask, event_class_mask);
+ }
+ DBUG_VOID_RETURN;
+}
+
+
+/**
Notify the audit system of an event
@param[in] thd
@@ -151,21 +175,8 @@ void mysql_audit_notify(THD *thd, uint e
{
va_list ap;
audit_handler_t *handlers= audit_handlers + event_class;
- unsigned long event_class_mask[MYSQL_AUDIT_CLASS_MASK_SIZE];
-
DBUG_ASSERT(event_class < audit_handlers_count);
-
- set_audit_mask(event_class_mask, event_class);
- /*
- Check to see if we have acquired the audit plugins for the
- required audit event classes.
- */
- if (thd && check_audit_mask(thd->audit_class_mask, event_class_mask))
- {
- plugin_foreach(thd, acquire_plugins, MYSQL_AUDIT_PLUGIN, &event_class);
- add_audit_mask(thd->audit_class_mask, event_class_mask);
- }
-
+ mysql_audit_acquire_plugins(thd, event_class);
va_start(ap, event_subtype);
(*handlers)(thd, event_subtype, ap);
va_end(ap);
@@ -448,6 +459,11 @@ static void event_class_dispatch(THD *th
#else /* EMBEDDED_LIBRARY */
+void mysql_audit_acquire_plugins(THD *thd, uint event_class)
+{
+}
+
+
void mysql_audit_initialize()
{
}
=== modified file 'sql/sql_audit.h'
--- a/sql/sql_audit.h 2010-03-31 14:05:33 +0000
+++ b/sql/sql_audit.h 2010-08-20 09:58:28 +0000
@@ -29,6 +29,7 @@ extern void mysql_audit_finalize();
extern void mysql_audit_init_thd(THD *thd);
extern void mysql_audit_free_thd(THD *thd);
+extern void mysql_audit_acquire_plugins(THD *thd, uint event_class);
extern void mysql_audit_notify(THD *thd, uint event_class,
=== modified file 'sql/sql_plugin.cc'
--- a/sql/sql_plugin.cc 2010-08-05 12:34:19 +0000
+++ b/sql/sql_plugin.cc 2010-08-20 09:58:28 +0000
@@ -29,7 +29,7 @@
#include "records.h" // init_read_record, end_read_record
#include <my_pthread.h>
#include <my_getopt.h>
-#include <mysql/plugin_audit.h>
+#include "sql_audit.h"
#include "lock.h" // MYSQL_LOCK_IGNORE_TIMEOUT
#define REPORT_TO_LOG 1
#define REPORT_TO_USER 2
@@ -1703,6 +1703,27 @@ bool mysql_install_plugin(THD *thd, cons
MYSQL_LOCK_IGNORE_TIMEOUT)))
DBUG_RETURN(TRUE);
+ /*
+ Pre-acquire audit plugins for events that may potentially occur
+ during [UN]INSTALL PLUGIN.
+
+ When audit event is triggered, audit subsystem acquires interested
+ plugins by walking through plugin list. Evidently plugin list
+ iterator protects plugin list by acquiring LOCK_plugin, see
+ plugin_foreach_with_mask().
+
+ On the other hand [UN]INSTALL PLUGIN is acquiring LOCK_plugin
+ rather for a long time.
+
+ When audit event is triggered during [UN]INSTALL PLUGIN, plugin
+ list iterator acquires the same lock (within the same thread)
+ second time.
+
+ This hack should be removed when LOCK_plugin is fixed so it
+ protects only what it supposed to protect.
+ */
+ mysql_audit_acquire_plugins(thd, MYSQL_AUDIT_GENERAL_CLASS);
+
mysql_mutex_lock(&LOCK_plugin);
mysql_rwlock_wrlock(&LOCK_system_variables_hash);
@@ -1783,6 +1804,27 @@ bool mysql_uninstall_plugin(THD *thd, co
if (! (table= open_ltable(thd, &tables, TL_WRITE, MYSQL_LOCK_IGNORE_TIMEOUT)))
DBUG_RETURN(TRUE);
+ /*
+ Pre-acquire audit plugins for events that may potentially occur
+ during [UN]INSTALL PLUGIN.
+
+ When audit event is triggered, audit subsystem acquires interested
+ plugins by walking through plugin list. Evidently plugin list
+ iterator protects plugin list by acquiring LOCK_plugin, see
+ plugin_foreach_with_mask().
+
+ On the other hand [UN]INSTALL PLUGIN is acquiring LOCK_plugin
+ rather for a long time.
+
+ When audit event is triggered during [UN]INSTALL PLUGIN, plugin
+ list iterator acquires the same lock (within the same thread)
+ second time.
+
+ This hack should be removed when LOCK_plugin is fixed so it
+ protects only what it supposed to protect.
+ */
+ mysql_audit_acquire_plugins(thd, MYSQL_AUDIT_GENERAL_CLASS);
+
mysql_mutex_lock(&LOCK_plugin);
if (!(plugin= plugin_find_internal(name, MYSQL_ANY_PLUGIN)))
{
Attachment: [text/bzr-bundle] bzr/svoj@sun.com-20100820095828-o96j4yv6p2y7bzg7.bundle
