bzr commit into mysql-6.0-backup branch (Sergey.Glukhov:2906) Bug#43357

[Sergey Glukhov]

#At file:///home/gluh/MySQL/mysql-6.0-backup/ based on revid:rafal.somla@stripped

 2906 Sergey Glukhov	2009-12-10
      Bug#43357 Server crash when selecting from INFORMATION_SCHEMA
      Server crashes in mysqld_list_processes() function on 
      pthread_mutex_unlock(&tmp->LOCK_thd_data) call.
      It happens because threads after its delete are still visible
      in thread list with destroyed LOCK_thd_data mutex.
      The fix is to remove deleted thd from thread list.
     @ sql/sql_class.cc
        added deleted thd removal from thread list
     @ sql/sql_list.h
        added is_linked() method

    modified:
      sql/sql_class.cc
      sql/sql_list.h
=== modified file 'sql/sql_class.cc'
--- a/sql/sql_class.cc	2009-12-02 22:58:41 +0000
+++ b/sql/sql_class.cc	2009-12-10 08:58:39 +0000
@@ -1067,6 +1067,8 @@ THD::~THD()
 {
   THD_CHECK_SENTRY(this);
   DBUG_ENTER("~THD()");
+  if (is_linked())
+    safe_mutex_assert_owner(&LOCK_thread_count);
   /* Ensure that no one is using THD */
   pthread_mutex_lock(&LOCK_thd_data);
   /*
@@ -1102,6 +1104,7 @@ THD::~THD()
   safeFree(db);
   free_root(&transaction.mem_root,MYF(0));
   mysys_var=0;					// Safety (shouldn't be needed)
+  unlink();
   pthread_mutex_destroy(&LOCK_thd_data);
 #ifndef DBUG_OFF
   dbug_sentry= THD_SENTRY_GONE;

=== modified file 'sql/sql_list.h'
--- a/sql/sql_list.h	2009-10-12 09:08:34 +0000
+++ b/sql/sql_list.h	2009-12-10 08:58:39 +0000
@@ -476,6 +476,7 @@ struct ilink
     if (next) next->prev=prev;
     prev=0 ; next=0;
   }
+  inline  bool is_linked() { return next || prev; }
   virtual ~ilink() { unlink(); }		/*lint -e1740 */
 };
 


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