Merge from 5.0

******
manual merge 5.0-bugteam --> 5.1-bugteam (bug 38816)

1 files changed, 31 insertions, 21 deletions

diff --git a/sql/sql_class.h b/sql/sql_class.h
index a758d24131b..f1b56551b50 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -631,22 +631,16 @@ public:
     we need to declare it char * because all table handlers are written
     in C and need to point to it.
 
-    Note that (A) if we set query = NULL, we must at the same time set
-    query_length = 0, and protect the whole operation with the
-    LOCK_thread_count mutex. And (B) we are ONLY allowed to set query to a
-    non-NULL value if its previous value is NULL. We do not need to protect
-    operation (B) with any mutex. To avoid crashes in races, if we do not
-    know that thd->query cannot change at the moment, one should print
+    Note that if we set query = NULL, we must at the same time set
+    query_length = 0, and protect the whole operation with
+    LOCK_thd_data mutex. To avoid crashes in races, if we do not
+    know that thd->query cannot change at the moment, we should print
     thd->query like this:
-      (1) reserve the LOCK_thread_count mutex;
-      (2) check if thd->query is NULL;
-      (3) if not NULL, then print at most thd->query_length characters from
-      it. We will see the query_length field as either 0, or the right value
-      for it.
-    Assuming that the write and read of an n-bit memory field in an n-bit
-    computer is atomic, we can avoid races in the above way. 
-    This printing is needed at least in SHOW PROCESSLIST and SHOW INNODB
-    STATUS.
+      (1) reserve the LOCK_thd_data mutex;
+      (2) print or copy the value of query and query_length
+      (3) release LOCK_thd_data mutex.
+    This printing is needed at least in SHOW PROCESSLIST and SHOW
+    ENGINE INNODB STATUS.
   */
   char *query;
   uint32 query_length;                          // current query length
@@ -678,7 +672,7 @@ public:
   virtual ~Statement();
 
   /* Assign execution context (note: not all members) of given stmt to self */
-  void set_statement(Statement *stmt);
+  virtual void set_statement(Statement *stmt);
   void set_n_backup_statement(Statement *stmt, Statement *backup);
   void restore_backup_statement(Statement *stmt, Statement *backup);
   /* return class type */
@@ -1298,7 +1292,15 @@ public:
   THR_LOCK_OWNER main_lock_id;          // To use for conventional queries
   THR_LOCK_OWNER *lock_id;              // If not main_lock_id, points to
                                         // the lock_id of a cursor.
-  pthread_mutex_t LOCK_delete;		// Locked before thd is deleted
+  /**
+    Protects THD data accessed from other threads:
+    - thd->query and thd->query_length (used by SHOW ENGINE
+      INNODB STATUS and SHOW PROCESSLIST
+    - thd->mysys_var (used by KILL statement and shutdown).
+    Is locked when THD is deleted.
+  */
+  pthread_mutex_t LOCK_thd_data;
+
   /* all prepared statements and cursors of this connection */
   Statement_map stmt_map;
   /*
@@ -1890,15 +1892,15 @@ public:
 #ifdef SIGNAL_WITH_VIO_CLOSE
   inline void set_active_vio(Vio* vio)
   {
-    pthread_mutex_lock(&LOCK_delete);
+    pthread_mutex_lock(&LOCK_thd_data);
     active_vio = vio;
-    pthread_mutex_unlock(&LOCK_delete);
+    pthread_mutex_unlock(&LOCK_thd_data);
   }
   inline void clear_active_vio()
   {
-    pthread_mutex_lock(&LOCK_delete);
+    pthread_mutex_lock(&LOCK_thd_data);
     active_vio = 0;
-    pthread_mutex_unlock(&LOCK_delete);
+    pthread_mutex_unlock(&LOCK_thd_data);
   }
   void close_active_vio();
 #endif
@@ -2271,6 +2273,14 @@ public:
   */
   void pop_internal_handler();
 
+  /** Overloaded to guard query/query_length fields */
+  virtual void set_statement(Statement *stmt);
+
+  /**
+    Assign a new value to thd->query.
+    Protected with LOCK_thd_data mutex.
+  */
+  void set_query(char *query_arg, uint32 query_length_arg);
 private:
   /** The current internal error handler for this thread, or NULL. */
   Internal_error_handler *m_internal_handler;