Fixed a deadlock problem when using LOCK TABLE in one thread and DROP TABLE in another

sql/lock.cc:
  Added functions to handle list of table name locks
sql/mysql_priv.h:
  Added functions to handle list of named locks
sql/sql_rename.cc:
  Use new general table name lock functions
sql/sql_table.cc:
  Require table name locks when doing drop table.
  This fixed a deadlock problem when using LOCK TABLE in one thread and DROP TABLE in another

4 files changed, 94 insertions, 28 deletions

diff --git a/sql/lock.cc b/sql/lock.cc
index 84d10d61366..e46e2aac7bc 100644
--- a/sql/lock.cc
+++ b/sql/lock.cc
@@ -416,10 +416,11 @@ int lock_table_name(THD *thd, TABLE_LIST *table_list)
 {
   TABLE *table;
   char  key[MAX_DBKEY_LENGTH];
+  char *db= table_list->db ? table_list->db : (thd->db ? thd->db : (char*) "");
   uint  key_length;
   DBUG_ENTER("lock_table_name");
 
-  key_length=(uint) (strmov(strmov(key,table_list->db)+1,table_list->real_name)
+  key_length=(uint) (strmov(strmov(key,db)+1,table_list->real_name)
 		     -key)+ 1;
 
   /* Only insert the table if we haven't insert it already */
@@ -447,7 +448,7 @@ 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, table_list->db, table_list->real_name))
+  if (remove_table_from_cache(thd, db, table_list->real_name))
     DBUG_RETURN(1);					// Table is in use
   DBUG_RETURN(0);
 }
@@ -490,6 +491,77 @@ bool wait_for_locked_table_names(THD *thd, TABLE_LIST *table_list)
   DBUG_RETURN(result);
 }
 
+
+/*
+  Lock all tables in list with a name lock
+
+  SYNOPSIS
+    lock_table_names()
+    thd			Thread handle
+    table_list		Names of tables to lock
+
+  NOTES
+    One must have a lock on LOCK_open when calling this
+
+  RETURN
+    0	ok
+    1	Fatal error (end of memory ?)
+*/
+
+bool lock_table_names(THD *thd, TABLE_LIST *table_list)
+{
+  bool got_all_locks=1;
+  TABLE_LIST *lock_table;
+
+  for (lock_table=table_list ; lock_table ; lock_table=lock_table->next)
+  {
+    int got_lock;
+    if ((got_lock=lock_table_name(thd,lock_table)) < 0)
+      goto end;					// Fatal error
+    if (got_lock)
+      got_all_locks=0;				// Someone is using table
+  }
+
+  /* If some table was in use, wait until we got the lock */
+  if (!got_all_locks && wait_for_locked_table_names(thd, table_list))
+    goto end;
+  return 0;
+
+end:
+  unlock_table_names(thd, table_list, lock_table);
+  return 1;
+}
+
+
+/*
+  Unlock all tables in list with a name lock
+
+  SYNOPSIS
+    unlock_table_names()
+    thd			Thread handle
+    table_list		Names of tables to unlock
+    last_table		Don't unlock any tables after this one.
+			(default 0, which will unlock all tables)
+
+  NOTES
+    One must have a lock on LOCK_open when calling this
+    This function will send a COND_refresh signal to inform other threads
+    that the name locks are removed
+
+  RETURN
+    0	ok
+    1	Fatal error (end of memory ?)
+*/
+
+void unlock_table_names(THD *thd, TABLE_LIST *table_list,
+			TABLE_LIST *last_table)
+{
+  for (TABLE_LIST *table=table_list ; table != last_table ; table=table->next)
+    unlock_table_name(thd,table);
+  pthread_cond_broadcast(&COND_refresh);
+}
+
+
 static void print_lock_error(int error)
 {
   int textno;
diff --git a/sql/mysql_priv.h b/sql/mysql_priv.h
index 49f1713bbc9..237a8a79acd 100644
--- a/sql/mysql_priv.h
+++ b/sql/mysql_priv.h
@@ -594,6 +594,9 @@ MYSQL_LOCK *mysql_lock_merge(MYSQL_LOCK *a,MYSQL_LOCK *b);
 int lock_table_name(THD *thd, TABLE_LIST *table_list);
 void unlock_table_name(THD *thd, TABLE_LIST *table_list);
 bool wait_for_locked_table_names(THD *thd, TABLE_LIST *table_list);
+bool lock_table_names(THD *thd, TABLE_LIST *table_list);
+void unlock_table_names(THD *thd, TABLE_LIST *table_list,
+			TABLE_LIST *last_table= 0);
 
 
 /* old unireg functions */
diff --git a/sql/sql_rename.cc b/sql/sql_rename.cc
index a6614f3f3f6..9eee8ccf7ac 100644
--- a/sql/sql_rename.cc
+++ b/sql/sql_rename.cc
@@ -31,8 +31,8 @@ static TABLE_LIST *rename_tables(THD *thd, TABLE_LIST *table_list,
 
 bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list)
 {
-  bool error=1,cerror,got_all_locks=1;
-  TABLE_LIST *lock_table,*ren_table=0;
+  bool error=1, cerror;
+  TABLE_LIST *ren_table= 0;
   DBUG_ENTER("mysql_rename_tables");
   
   /* Avoid problems with a rename on a table that we have locked or
@@ -45,23 +45,11 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list)
   }
       
   VOID(pthread_mutex_lock(&LOCK_open));
-  for (lock_table=table_list ; lock_table ; lock_table=lock_table->next)
-  {
-    int got_lock;
-    if ((got_lock=lock_table_name(thd,lock_table)) < 0)
-      goto end;
-    if (got_lock)
-      got_all_locks=0;
-  }
-  
-  if (!got_all_locks && wait_for_locked_table_names(thd,table_list))
-    goto end;
+  if (lock_table_names(thd, table_list))
+    goto err;
 
-  if (!(ren_table=rename_tables(thd,table_list,0)))
-    error=0;
-  
-end:
-  if (ren_table)
+  error= 0;
+  if ((ren_table=rename_tables(thd,table_list,0)))
   {
     /* Rename didn't succeed;  rename back the tables in reverse order */
     TABLE_LIST *prev=0,*table;
@@ -83,7 +71,7 @@ end:
     table=table->next->next;			// Skipp error table
     /* Revert to old names */
     rename_tables(thd, table, 1);
-    /* Note that lock_table == 0 here, so the unlock loop will work */
+    error= 1;
   }
 
   /* Lets hope this doesn't fail as the result will be messy */ 
@@ -103,9 +91,9 @@ end:
     send_ok(&thd->net);
   }
 
-  for (TABLE_LIST *table=table_list ; table != lock_table ; table=table->next)
-    unlock_table_name(thd,table);
-  pthread_cond_broadcast(&COND_refresh);
+  unlock_table_names(thd,table_list);
+
+err:
   pthread_mutex_unlock(&LOCK_open);
   DBUG_RETURN(error);
 }
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 4691c2fd494..2ff7c9c1a75 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -49,7 +49,7 @@ int mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists)
   char	path[FN_REFLEN];
   String wrong_tables;
   bool some_tables_deleted=0;
-  uint error;
+  uint error= 1;
   db_type table_type;
   TABLE_LIST *table;
   DBUG_ENTER("mysql_rm_table");
@@ -66,7 +66,6 @@ int mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists)
     {
       my_error(ER_TABLE_NOT_LOCKED_FOR_WRITE,MYF(0),
 	       tables->real_name);
-      error = 1;
       goto err;
     }
     while (global_read_lock && ! thd->killed)
@@ -76,9 +75,12 @@ int mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists)
 
   }
   
+  if (lock_table_names(thd, tables))
+    goto err;
+
   for (table=tables ; table ; table=table->next)
   {
-    char *db=table->db ? table->db : thd->db;
+    char *db=table->db ? table->db : (thd->db ? thd->db : (char*) "");
     if (!close_temporary_table(thd, db, table->real_name))
     {
       some_tables_deleted=1;			// Log query
@@ -149,9 +151,10 @@ int mysql_rm_table(THD *thd,TABLE_LIST *tables, my_bool if_exists)
   }
   
   error = 0;
+  unlock_table_names(thd, tables);
+
  err:  
   pthread_mutex_unlock(&LOCK_open);
-  VOID(pthread_cond_broadcast(&COND_refresh)); // Signal to refresh
 
   pthread_mutex_lock(&thd->mysys_var->mutex);
   thd->mysys_var->current_mutex= 0;