Commit e1c8d9c9 authored by unknown's avatar unknown
Browse files

Fix for bug #16593 "Deadlock or crash in stress test for case where 

trigger starts trigger".

In short, the deadlock/crash happened when execution of statement, which used
stored functions or activated triggers, coincided with alteration of the
tables used by these functions or triggers (in highly concurrent environment).

Bug was caused by the incorrect handling of tables from prelocked set in
open_tables() functions in situations when refresh happened. This fix replaces
old smart but not very robust way of handling tables after refresh (which was
closing only old tables), with new one which simply closes all tables opened so
far and restarts open_tables().
Also fixed handling of temporary tables in close_tables_for_reopen().

No test case present since bug manifests itself only in concurrent environment.


sql/mysql_priv.h:
  In order to handle correctly case when table list completely consists from tables
  from prelocked set close_tables_for_reopen() have to accept table list as in/out
  parameter.
sql/sql_base.cc:
  open_tables():
    Removed part of comment  which was out of date.
    Changed handling of case when refresh happens during opening of tables, now
    instead of having code which decides for each table if it should be closed
    we simply close all tables. Old code also incorrectly handled tables from
    prelocked set in this situation which resulted in bug #16593 "Deadlock or
    crash in stress test for case where triggers starting trigger".
  close_tables_for_reopen():
    Now we correctly handle the case when table list completely consists from
    tables from prelocked set. Also now we simply close all tables instead
    leaving temporary tables non-closed (such approach allows easily handle
    correctly tables from prelocked set).
sql/sql_prepare.cc:
  In order to handle correctly case when table list completely consists from tables
  from prelocked set close_tables_for_reopen() have to accept table list as in/out
  parameter.
sql/sql_update.cc:
  In order to handle correctly case when table list completely consists from tables
  from prelocked set close_tables_for_reopen() have to accept table list as in/out
  parameter.
parent 86733db8

sql/mysql_priv.h

+1 −1
Original line number Diff line number Diff line
@@ -981,7 +981,7 @@ void free_io_cache(TABLE *entry); 
void intern_close_table(TABLE *entry);

bool close_thread_table(THD *thd, TABLE **table_ptr);

void close_temporary_tables(THD *thd);

void close_tables_for_reopen(THD *thd, TABLE_LIST *tables);

void close_tables_for_reopen(THD *thd, TABLE_LIST **tables);

TABLE_LIST *find_table_in_list(TABLE_LIST *table,

                               uint offset_to_list,

                               const char *db_name,

sql/sql_base.cc

+27 −57
Original line number Diff line number Diff line
@@ -1982,22 +1982,11 @@ int open_tables(THD *thd, TABLE_LIST **start, uint *counter, uint flags) 
    statement for which table list for prelocking is already built, let

    us cache routines and try to build such table list.



    NOTE: We can't delay prelocking until we will met some sub-statement

    which really uses tables, since this will imply that we have to restore

    its table list to be able execute it in some other context.

    And current views implementation assumes that view tables are added to

    global table list only once during PS preparing/first SP execution.

    Also locking at earlier stage is probably faster altough may decrease

    concurrency a bit.



    NOTE: We will mark statement as requiring prelocking only if we will

    have non empty table list. But this does not guarantee that in prelocked

    mode we will have some locked tables, because queries which use only

    derived/information schema tables and views possible. Thus "counter"

    may be still zero for prelocked statement...



    NOTE: The above notes may be out of date. Please wait for psergey to

          document new prelocked behavior.

  */



  if (!thd->prelocked_mode && !thd->lex->requires_prelocking() &&
@@ -2083,48 +2072,23 @@ int open_tables(THD *thd, TABLE_LIST **start, uint *counter, uint flags) 


      if (refresh)				// Refresh in progress

      {

	/* close all 'old' tables used by this thread */

	pthread_mutex_lock(&LOCK_open);

	// if query_id is not reset, we will get an error

	// re-opening a temp table

	thd->version=refresh_version;

	TABLE **prev_table= &thd->open_tables;

	bool found=0;

	for (TABLE_LIST *tmp= *start; tmp; tmp= tmp->next_global)

	{

	  /* Close normal (not temporary) changed tables */

	  if (tmp->table && ! tmp->table->s->tmp_table)

	  {

	    if (tmp->table->s->version != refresh_version ||

		! tmp->table->db_stat)

	    {

	      VOID(hash_delete(&open_cache,(byte*) tmp->table));

	      tmp->table=0;

	      found=1;

	    }

	    else

	    {

	      *prev_table= tmp->table;		// Relink open list

	      prev_table= &tmp->table->next;

	    }

	  }

	}

	*prev_table=0;

	pthread_mutex_unlock(&LOCK_open);

	if (found)

	  VOID(pthread_cond_broadcast(&COND_refresh)); // Signal to refresh

        /*

          Let us prepare for recalculation of set of prelocked tables.

          First we pretend that we have finished calculation which we

          were doing currently. Then we restore list of tables to be

          opened and set of used routines to the state in which they were

          before first open_tables() call for this statement (i.e. before

          we have calculated current set of tables for prelocking).

          We have met name-locked or old version of table. Now we have

          to close all tables which are not up to date. We also have to

          throw away set of prelocked tables (and thus close tables from

          this set that were open by now) since it possible that one of

          tables which determined its content was changed.



          Instead of implementing complex/non-robust logic mentioned

          above we simply close and then reopen all tables.



          In order to prepare for recalculation of set of prelocked tables

          we pretend that we have finished calculation which we were doing

          currently.

        */

        if (query_tables_last_own)

          thd->lex->mark_as_requiring_prelocking(query_tables_last_own);

        thd->lex->chop_off_not_own_tables();

        sp_remove_not_own_routines(thd->lex);

        close_tables_for_reopen(thd, start);

	goto restart;

      }

      result= -1;				// Fatal error
@@ -2335,7 +2299,7 @@ int simple_open_n_lock_tables(THD *thd, TABLE_LIST *tables) 
      break;

    if (!need_reopen)

      DBUG_RETURN(-1);

    close_tables_for_reopen(thd, tables);

    close_tables_for_reopen(thd, &tables);

  }

  DBUG_RETURN(0);

}
@@ -2372,7 +2336,7 @@ bool open_and_lock_tables(THD *thd, TABLE_LIST *tables) 
      break;

    if (!need_reopen)

      DBUG_RETURN(-1);

    close_tables_for_reopen(thd, tables);

    close_tables_for_reopen(thd, &tables);

  }

  if (mysql_handle_derived(thd->lex, &mysql_derived_prepare) ||

      (thd->fill_derived_tables() &&
@@ -2600,18 +2564,24 @@ int lock_tables(THD *thd, TABLE_LIST *tables, uint count, bool *need_reopen) 


  SYNOPSIS

    close_tables_for_reopen()

      thd     Thread context

      tables  List of tables which we were trying to open and lock

      thd    in     Thread context

      tables in/out List of tables which we were trying to open and lock



*/



void close_tables_for_reopen(THD *thd, TABLE_LIST *tables)

void close_tables_for_reopen(THD *thd, TABLE_LIST **tables)

{

  /*

    If table list consists only from tables from prelocking set, table list

    for new attempt should be empty, so we have to update list's root pointer.

  */

  if (thd->lex->first_not_own_table() == *tables)

    *tables= 0;

  thd->lex->chop_off_not_own_tables();

  sp_remove_not_own_routines(thd->lex);

  for (TABLE_LIST *tmp= tables; tmp; tmp= tmp->next_global)

    if (tmp->table && !tmp->table->s->tmp_table)

  for (TABLE_LIST *tmp= *tables; tmp; tmp= tmp->next_global)

    tmp->table= 0;

  mark_used_tables_as_free_for_reuse(thd, thd->temporary_tables);

  close_thread_tables(thd);

}

sql/sql_prepare.cc

+1 −1
Original line number Diff line number Diff line
@@ -1135,7 +1135,7 @@ static int mysql_test_update(Prepared_statement *stmt, 
      break;

    if (!need_reopen)

      goto error;

    close_tables_for_reopen(thd, table_list);

    close_tables_for_reopen(thd, &table_list);

  }



  /*

sql/sql_update.cc

+2 −2
Original line number Diff line number Diff line
@@ -158,7 +158,7 @@ int mysql_update(THD *thd, 
      break;

    if (!need_reopen)

      DBUG_RETURN(1);

    close_tables_for_reopen(thd, table_list);

    close_tables_for_reopen(thd, &table_list);

  }



  if (mysql_handle_derived(thd->lex, &mysql_derived_prepare) ||
@@ -813,7 +813,7 @@ bool mysql_multi_update_prepare(THD *thd) 
    for (TABLE_LIST *tbl= table_list; tbl; tbl= tbl->next_global)

      tbl->cleanup_items();



    close_tables_for_reopen(thd, table_list);

    close_tables_for_reopen(thd, &table_list);

    goto reopen_tables;

  }