Bug #10600

remove_table_from_cache fails to signal other thread and gets
blocked when other thread also gets blocked


include/thr_lock.h:
  Report if any threads was signalled
mysys/thr_lock.c:
  Report if any threads was signalled
sql/lock.cc:
  Report if any threads was signalled
  Use new interface for remove_table_from_cache
sql/mysql_priv.h:
  New interface for remove_table_from_cache
  + mysql_lock_abort_for_thread
sql/sql_base.cc:
  Use new interface of remove_table_cache
  Rewrote remove_table_from_cache to fix bug
sql/sql_table.cc:
  Use new interface of remove_table_from_cache

include/thr_lock.h

@@ -107,7 +107,7 @@ void thr_unlock(THR_LOCK_DATA *data);
 int thr_multi_lock(THR_LOCK_DATA **data,uint count);
 void thr_multi_unlock(THR_LOCK_DATA **data,uint count);
 void thr_abort_locks(THR_LOCK *lock);
-void thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread);
+bool thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread);
 void thr_print_locks(void);		/* For debugging */
 my_bool thr_upgrade_write_delay_lock(THR_LOCK_DATA *data);
 my_bool thr_reschedule_write_lock(THR_LOCK_DATA *data);

mysys/thr_lock.c

@@ -966,9 +966,10 @@ void thr_abort_locks(THR_LOCK *lock)
   This is used to abort all locks for a specific thread
 */
 
-void thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread)
+bool thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread)
 {
   THR_LOCK_DATA *data;
+  bool found= FALSE;
   DBUG_ENTER("thr_abort_locks_for_thread");
 
   pthread_mutex_lock(&lock->mutex);
@@ -978,6 +979,7 @@ void thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread)
     {
       DBUG_PRINT("info",("Aborting read-wait lock"));
       data->type= TL_UNLOCK;			/* Mark killed */
+      found= TRUE;
       pthread_cond_signal(data->cond);
       data->cond= 0;				/* Removed from list */
 
@@ -993,6 +995,7 @@ void thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread)
     {
       DBUG_PRINT("info",("Aborting write-wait lock"));
       data->type= TL_UNLOCK;
+      found= TRUE;
       pthread_cond_signal(data->cond);
       data->cond= 0;
 
@@ -1003,7 +1006,7 @@ void thr_abort_locks_for_thread(THR_LOCK *lock, pthread_t thread)
     }
   }
   pthread_mutex_unlock(&lock->mutex);
-  DBUG_VOID_RETURN;
+  DBUG_RETURN(found);
 }
 
 

sql/lock.cc

@@ -333,20 +333,25 @@ void mysql_lock_abort(THD *thd, TABLE *table)
 
 /* Abort one thread / table combination */
 
-void mysql_lock_abort_for_thread(THD *thd, TABLE *table)
+bool mysql_lock_abort_for_thread(THD *thd, TABLE *table)
 {
   MYSQL_LOCK *locked;
   TABLE *write_lock_used;
+  bool result= FALSE;
   DBUG_ENTER("mysql_lock_abort_for_thread");
 
   if ((locked = get_lock_data(thd,&table,1,1,&write_lock_used)))
   {
     for (uint i=0; i < locked->lock_count; i++)
-      thr_abort_locks_for_thread(locked->locks[i]->lock,
+    {
+      bool found;
+      found= thr_abort_locks_for_thread(locked->locks[i]->lock,
 	         			 table->in_use->real_id);
+      result|= found;
+    }
     my_free((gptr) locked,MYF(0));
   }
-  DBUG_VOID_RETURN;
+  DBUG_RETURN(result);
 }
 
 
@@ -542,8 +547,15 @@ int lock_table_name(THD *thd, TABLE_LIST *table_list)
     my_free((gptr) table,MYF(0));
     DBUG_RETURN(-1);
   }
-  if (remove_table_from_cache(thd, db, table_list->real_name))
+  
+  {
+    uint flags= 0;
+    if (remove_table_from_cache(thd, db,
+                                table_list->real_name, flags))
+    {
       DBUG_RETURN(1);				// Table is in use
+    }
+  }
   DBUG_RETURN(0);
 }
 

sql/mysql_priv.h

@@ -606,8 +606,11 @@ bool rename_temporary_table(THD* thd, TABLE *table, const char *new_db,
 			    const char *table_name);
 void remove_db_from_cache(const my_string db);
 void flush_tables();
+#define OWNED_BY_THD_FLAG 1
+#define WAIT_OTHER_THREAD_FLAG 2
+#define CHECK_KILLED_FLAG 4
 bool remove_table_from_cache(THD *thd, const char *db, const char *table,
-			     bool return_if_owned_by_thd=0);
+                             uint flags);
 bool close_cached_tables(THD *thd, bool wait_for_refresh, TABLE_LIST *tables);
 void copy_field_from_tmp_record(Field *field,int offset);
 int fill_record(List<Item> &fields,List<Item> &values, bool ignore_errors);
@@ -776,7 +779,7 @@ void mysql_unlock_read_tables(THD *thd, MYSQL_LOCK *sql_lock);
 void mysql_unlock_some_tables(THD *thd, TABLE **table,uint count);
 void mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table);
 void mysql_lock_abort(THD *thd, TABLE *table);
-void mysql_lock_abort_for_thread(THD *thd, TABLE *table);
+bool mysql_lock_abort_for_thread(THD *thd, TABLE *table);
 MYSQL_LOCK *mysql_lock_merge(MYSQL_LOCK *a,MYSQL_LOCK *b);
 bool lock_global_read_lock(THD *thd);
 void unlock_global_read_lock(THD *thd);

sql/sql_base.cc

@@ -370,7 +370,9 @@ bool close_cached_tables(THD *thd, bool if_wait_for_refresh,
     bool found=0;
     for (TABLE_LIST *table=tables ; table ; table=table->next)
     {
-      if (remove_table_from_cache(thd, table->db, table->real_name, 1))
+      uint flags= OWNED_BY_THD_FLAG;
+      if (remove_table_from_cache(thd, table->db, table->real_name,
+                                  flags))
 	found=1;
     }
     if (!found)
@@ -2407,15 +2409,22 @@ void flush_tables()
 */
 
 bool remove_table_from_cache(THD *thd, const char *db, const char *table_name,
-			     bool return_if_owned_by_thd)
+                             uint flags)
 {
   char key[MAX_DBKEY_LENGTH];
   uint key_length;
   TABLE *table;
-  bool result=0;
+  bool result=0, signalled= 0;
+  bool return_if_owned_by_thd= flags & OWNED_BY_THD_FLAG;
+  bool wait_for_other_thread= flags & WAIT_OTHER_THREAD_FLAG;
+  bool check_killed_flag= flags & CHECK_KILLED_FLAG;
   DBUG_ENTER("remove_table_from_cache");
 
   key_length=(uint) (strmov(strmov(key,db)+1,table_name)-key)+1;
+  do
+  {
+    result= signalled= 0;
+
     for (table=(TABLE*) hash_search(&open_cache,(byte*) key,key_length) ;
          table;
          table = (TABLE*) hash_next(&open_cache,(byte*) key,key_length))
@@ -2441,6 +2450,7 @@ bool remove_table_from_cache(THD *thd, const char *db, const char *table_name,
 	  if (in_use->mysys_var->current_cond)
 	  {
 	    pthread_mutex_lock(in_use->mysys_var->current_mutex);
+            signalled= 1;
 	    pthread_cond_broadcast(in_use->mysys_var->current_cond);
 	    pthread_mutex_unlock(in_use->mysys_var->current_mutex);
 	  }
@@ -2455,7 +2465,11 @@ bool remove_table_from_cache(THD *thd, const char *db, const char *table_name,
 	     thd_table= thd_table->next)
         {
 	  if (thd_table->db_stat)		// If table is open
-	  mysql_lock_abort_for_thread(thd, thd_table);
+          {
+            bool found;
+	    found= mysql_lock_abort_for_thread(thd, thd_table);
+            signalled|= found;
+          }
         }
       }
       else
@@ -2463,6 +2477,38 @@ bool remove_table_from_cache(THD *thd, const char *db, const char *table_name,
     }
     while (unused_tables && !unused_tables->version)
       VOID(hash_delete(&open_cache,(byte*) unused_tables));
+    if (result && wait_for_other_thread)
+    {
+      if (!check_killed_flag || !thd->killed)
+      {
+        if (likely(signalled))
+        {
+          dropping_tables++;
+          (void) pthread_cond_wait(&COND_refresh, &LOCK_open);
+          dropping_tables--;
+          continue;
+        }
+        else
+        {
+          /*
+            It can happen that another thread has opened the
+            table but has not yet locked any table at all. Since
+            it can be locked waiting for a table that our thread
+            has done LOCK TABLE x WRITE on previously, we need to
+            ensure that the thread actually hears our signal
+            before we go to sleep. Thus we wait for a short time
+            and then we retry another loop in the
+            remove_table_from_cache routine.
+          */
+          pthread_mutex_unlock(&LOCK_open);
+          my_sleep(10);
+          pthread_mutex_lock(&LOCK_open);
+          continue;
+        }
+      }
+    }
+    break;
+  } while (1);
   DBUG_RETURN(result);
 }
 

sql/sql_table.cc

@@ -178,6 +178,7 @@ int mysql_rm_table_part2(THD *thd, TABLE_LIST *tables, bool if_exists,
   for (table=tables ; table ; table=table->next)
   {
     char *db=table->db;
+    uint flags;
     mysql_ha_flush(thd, table, MYSQL_HA_CLOSE_FINAL);
     if (!close_temporary_table(thd, db, table->real_name))
     {
@@ -186,12 +187,8 @@ int mysql_rm_table_part2(THD *thd, TABLE_LIST *tables, bool if_exists,
     }
 
     abort_locked_tables(thd,db,table->real_name);
-    while (remove_table_from_cache(thd,db,table->real_name) && !thd->killed)
-    {
-      dropping_tables++;
-      (void) pthread_cond_wait(&COND_refresh,&LOCK_open);
-      dropping_tables--;
-    }
+    flags= WAIT_OTHER_THREAD_FLAG | CHECK_KILLED_FLAG;
+    remove_table_from_cache(thd,db,table->real_name,flags);
     drop_locked_tables(thd,db,table->real_name);
     if (thd->killed)
       DBUG_RETURN(-1);
@@ -979,6 +976,7 @@ mysql_rename_table(enum db_type base,
 static void wait_while_table_is_used(THD *thd,TABLE *table,
 				     enum ha_extra_function function)
 {
+  uint flags;
   DBUG_PRINT("enter",("table: %s", table->real_name));
   DBUG_ENTER("wait_while_table_is_used");
   safe_mutex_assert_owner(&LOCK_open);
@@ -988,13 +986,9 @@ static void wait_while_table_is_used(THD *thd,TABLE *table,
   mysql_lock_abort(thd, table);			// end threads waiting on lock
 
   /* Wait until all there are no other threads that has this table open */
-  while (remove_table_from_cache(thd,table->table_cache_key,
-				 table->real_name))
-  {
-    dropping_tables++;
-    (void) pthread_cond_wait(&COND_refresh,&LOCK_open);
-    dropping_tables--;
-  }
+  flags= WAIT_OTHER_THREAD_FLAG;
+  remove_table_from_cache(thd,table->table_cache_key,
+                          table->real_name,flags);
   DBUG_VOID_RETURN;
 }
 
@@ -1306,18 +1300,14 @@ static int mysql_admin_table(THD* thd, TABLE_LIST* tables,
     /* Close all instances of the table to allow repair to rename files */
     if (lock_type == TL_WRITE && table->table->version)
     {
+      uint flags;
       pthread_mutex_lock(&LOCK_open);
       const char *old_message=thd->enter_cond(&COND_refresh, &LOCK_open,
 					      "Waiting to get writelock");
       mysql_lock_abort(thd,table->table);
-      while (remove_table_from_cache(thd, table->table->table_cache_key,
-				     table->table->real_name) &&
-	     ! thd->killed)
-      {
-	dropping_tables++;
-	(void) pthread_cond_wait(&COND_refresh,&LOCK_open);
-	dropping_tables--;
-      }
+      flags= WAIT_OTHER_THREAD_FLAG | CHECK_KILLED_FLAG;
+      remove_table_from_cache(thd, table->table->table_cache_key,
+                              table->table->real_name, flags);
       thd->exit_cond(old_message);
       if (thd->killed)
 	goto err;
@@ -1382,9 +1372,10 @@ static int mysql_admin_table(THD* thd, TABLE_LIST* tables,
       table->table->version=0;			// Force close of table
     else if (open_for_modify)
     {
+      uint flags= 0;
       pthread_mutex_lock(&LOCK_open);
       remove_table_from_cache(thd, table->table->table_cache_key,
-			      table->table->real_name);
+			      table->table->real_name, flags);
       pthread_mutex_unlock(&LOCK_open);
       /* May be something modified consequently we have to invalidate cache */
       query_cache_invalidate3(thd, table->table, 0);
@@ -2108,8 +2099,9 @@ int mysql_alter_table(THD *thd,char *new_db, char *new_name,
     */
     if (table)
     {
+      uint flags= 0;
       VOID(table->file->extra(HA_EXTRA_FORCE_REOPEN)); // Use new file
-      remove_table_from_cache(thd,db,table_name); // Mark all in-use copies old
+      remove_table_from_cache(thd,db,table_name,flags);// Mark in-use copies old
       mysql_lock_abort(thd,table);		 // end threads waiting on lock
     }
     VOID(quick_rm_table(old_db_type,db,old_name));