bk commit into 5.1 tree (acurtis:1.2579)

[antony]

Below is the list of changes that have just been committed into a local
5.1 repository of antony. When antony does a push these changes will
be propagated to the main repository and, within 24 hours after the
push, to the public repository.
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ChangeSet@stripped, 2007-04-18 00:17:05-07:00, acurtis@stripped +1 -0
  WL#2936
    Fix for ndb initialization deadlock.
    Changes so that LOCK_plugin is released before calling plugin initialization function
    so that deadlock is avoided should the plugin create THD objects.
    Plugin installation is still serialized.

  sql/sql_plugin.cc@stripped, 2007-04-18 00:17:01-07:00, acurtis@stripped +34 -0
    WL2936
      Changes so that LOCK_plugin is released before calling plugin initialization
function
      so that deadlock is avoided should the plugin create THD objects.
      Plugin installation is still serialized.

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	acurtis
# Host:	ltamd64.xiphis.org
# Root:	/home/antony/work2/mysql-5.1-wl2936

--- 1.49/sql/sql_plugin.cc	2007-04-18 00:17:19 -07:00
+++ 1.50/sql/sql_plugin.cc	2007-04-18 00:17:19 -07:00
@@ -97,6 +97,8 @@
 static HASH plugin_hash[MYSQL_MAX_PLUGIN_TYPE_NUM];
 /* we are always manipulating ref count, so a rwlock is unneccessary */
 static pthread_mutex_t LOCK_plugin;
+static pthread_cond_t COND_plugin;
+static THD *plugin_update_thd= 0;
 static bool initialized= 0;
 static bool reap_needed= false;
 
@@ -974,6 +976,13 @@
   DBUG_ENTER("plugin_initialize");
 
   safe_mutex_assert_owner(&LOCK_plugin);
+  /*
+    A little bit of voodoo here: During plugin subsystem initialization,
+	current_thd will return NULL. After mysqld startup is complete, later
+	calls to mysql_install_plugin will be set to current THD.
+   */
+  DBUG_ASSERT(plugin_update_thd == current_thd);
+  pthread_mutex_unlock(&LOCK_plugin);
 
   if (plugin_type_initialize[plugin->plugin->type])
   {
@@ -981,6 +990,7 @@
     {
       sql_print_error("Plugin '%s' registration as a %s failed.",
                       plugin->name.str,
plugin_type_names[plugin->plugin->type].str);
+      pthread_mutex_lock(&LOCK_plugin);
       goto err;
     }
   }
@@ -990,10 +1000,12 @@
     {
       sql_print_error("Plugin '%s' init function returned error.",
                       plugin->name.str);
+      pthread_mutex_lock(&LOCK_plugin);
       goto err;
     }
   }
 
+  pthread_mutex_lock(&LOCK_plugin);
   plugin->state= PLUGIN_IS_READY;
 
   if (plugin->plugin->status_vars)
@@ -1086,6 +1098,7 @@
 
 
   pthread_mutex_init(&LOCK_plugin, MY_MUTEX_INIT_FAST);
+  pthread_cond_init(&COND_plugin, NULL);
 
   if (my_init_dynamic_array(&plugin_dl_array,
                             sizeof(struct st_plugin_dl),16,16) ||
@@ -1533,6 +1546,7 @@
     pthread_mutex_unlock(&LOCK_plugin);
 
     initialized= 0;
+    pthread_cond_destroy(&COND_plugin);
     pthread_mutex_destroy(&LOCK_plugin);
 
     my_afree(plugins);
@@ -1581,6 +1595,11 @@
     DBUG_RETURN(TRUE);
 
   pthread_mutex_lock(&LOCK_plugin);
+  DBUG_ASSERT(thd != plugin_update_thd);
+  while (plugin_update_thd)
+    pthread_cond_wait(&COND_plugin, &LOCK_plugin);
+  plugin_update_thd= thd;
+  
   rw_wrlock(&LOCK_system_variables_hash);
   error= plugin_add(thd->mem_root, name, dl, &argc, NULL, REPORT_TO_USER);
   rw_unlock(&LOCK_system_variables_hash);
@@ -1606,6 +1625,8 @@
     goto deinit;
   }
 
+  plugin_update_thd= 0;
+  pthread_cond_signal(&COND_plugin);
   pthread_mutex_unlock(&LOCK_plugin);
   DBUG_RETURN(FALSE);
 deinit:
@@ -1613,6 +1634,8 @@
   reap_needed= true;
   reap_plugins();
 err:
+  plugin_update_thd= 0;
+  pthread_cond_signal(&COND_plugin);
   pthread_mutex_unlock(&LOCK_plugin);
   DBUG_RETURN(TRUE);
 }
@@ -1634,6 +1657,11 @@
     DBUG_RETURN(TRUE);
 
   pthread_mutex_lock(&LOCK_plugin);
+  DBUG_ASSERT(thd != plugin_update_thd);
+  while (plugin_update_thd)
+    pthread_cond_wait(&COND_plugin, &LOCK_plugin);
+  plugin_update_thd= thd;
+  
   if (!(plugin= plugin_find_internal(name, MYSQL_ANY_PLUGIN)))
   {
     my_error(ER_SP_DOES_NOT_EXIST, MYF(0), "PLUGIN", name->str);
@@ -1669,8 +1697,14 @@
       DBUG_RETURN(TRUE);
     }
   }
+  
+  plugin_update_thd= 0;
+  pthread_cond_signal(&COND_plugin);  
   DBUG_RETURN(FALSE);
+
 err:
+  plugin_update_thd= 0;
+  pthread_cond_signal(&COND_plugin);
   pthread_mutex_unlock(&LOCK_plugin);
   DBUG_RETURN(TRUE);
 }