Commit 374ea106 authored by unknown's avatar unknown
Browse files

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
parent 391bc11a

sql/lock.cc

+74 −2
Original line number Diff line number Diff line
@@ -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;

sql/mysql_priv.h

+3 −0
Original line number Diff line number Diff line
@@ -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 */

sql/sql_rename.cc

+10 −22
Original line number Diff line number Diff line
@@ -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)

  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 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list) 
    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 @@ bool mysql_rename_tables(THD *thd, TABLE_LIST *table_list) 
    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);

}

sql/sql_table.cc

+7 −4
Original line number Diff line number Diff line
@@ -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;