Commit d5303b8a authored by unknown's avatar unknown
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Fix for bug #12704 "Server crashes during trigger execution". 

This bug occurs when some trigger for table used by DML statement is created
or changed while statement was waiting in lock_tables(). In this situation
prelocking set which we have calculated becames invalid which can easily lead
to errors and even in some cases to crashes.

With proposed patch we no longer silently reopen tables in lock_tables(),
instead caller of lock_tables() becomes responsible for reopening tables and
recalculation of prelocking set.


mysql-test/t/trigger.test:
  Added tests for bug #12704 "Server crashes during trigger execution".
  Unfortunately these tests rely on the order in which tables are locked
  by statement so they are non-determenistic and therefore should be disabled.
sql/lock.cc:
  mysql_lock_tables():
    Now instead of always reopening altered or dropped tables by itself
    mysql_lock_tables() can notify upper level and rely on caller doing this.
sql/mysql_priv.h:
  Now mysql_lock_tables() can either reopen deleted or altered tables by itself
  or notify caller about such situation through 'need_reopen' argument and rely
  on it in this.
  Also lock_tables() has new 'need_reopen' out parameter through which it
  notifies caller that some tables were altered or dropped so he needs to reopen
  them (and rebuild prelocking set some triggers may change or simply appear).
sql/sp.cc:
  sp_add_used_routine():
    To be able to restore LEX::sroutines_list to its state right after parsing
    we now adjust  LEX::sroutines_list_own_last/sroutines_list_own_elements when
    we add directly used routine.
  sp_remove_not_own_routines():
    Added procedure for restoring LEX::sroutines/sroutines_list to their state
    right after parsing (by throwing out non-directly used routines).
  sp_cache_routines_and_add_tables_for_view()/sp_update_stmt_used_routines():
    We should use LEX::sroutines_list instead of LEX::sroutines as source of
    routines used by view, since LEX::sroutines is not availiable for view
    on second attempt to open it (see comment in open_tables() about it).
sql/sp.h:
  sp_remove_not_own_routines():
    Added procedure for restoring LEX::sroutines/sroutines_list to their state
    right after parsing (by throwing out non-directly used routines).
sql/sp_head.cc:
  Removed assert which is no longer always true.
sql/sql_base.cc:
  reopen_table():
    When we re-open table and do shallow copy of TABLE object we should adjust
    pointers to it in associated Table_triggers_list object. Removed nil
    operation.
  open_tables():
    Now this function is able to rebuild prelocking set for statement if it is
    needed. It also correctly handles FLUSH TABLES which may occur during its
    execution.
  lock_tables():
    Instead of allowing mysql_lock_tables() to silently reopen altered or dropped
    tables let us notify caller and rely on that it will do reopen itself.
    This solves the problem when trigger suddenly appears or changed during
    mysq_lock_tables().
  close_tables_for_reopen():
    Added routine for properly preparing for reopening of tables and recalculation
    of set of prelocked tables.
sql/sql_handler.cc:
  Here we let mysql_lock_tables() to reopen dropped or altered tables by itself.
sql/sql_insert.cc:
  Here we let mysql_lock_tables() to reopen dropped or altered tables by itself.
sql/sql_lex.cc:
  LEX:
    Added 'sroutines_list_own_last' and 'sroutines_list_own_elements' members
    which are used for keeping state in which 'sroutines_list' was right after
    statement parsing (and for restoring of this list to this state).
sql/sql_lex.h:
  LEX:
    Added 'sroutines_list_own_last' and 'sroutines_list_own_elements' members
    which are used for keeping state in which 'sroutines_list' was right after
    statement parsing (and for restoring of this list to this state).
    Added chop_off_not_own_tables() method to simplify throwing away list
    of implicitly used (prelocked) tables.
sql/sql_prepare.cc:
  Now instead of silently reopening altered or dropped tables in
  lock_tables() we notify caller and rely on that the caller will
  reopen tables.
sql/sql_table.cc:
  Here we let mysql_lock_tables() to reopen dropped or altered tables by itself.
sql/sql_trigger.cc:
  Added Table_triggers_list::set_table() method to adjust Table_triggers_list
  to new pointer to TABLE instance.
sql/sql_trigger.h:
  Added Table_triggers_list::set_table() method to adjust Table_triggers_list
  to new pointer to TABLE instance.
sql/sql_update.cc:
  Now instead of silently reopening altered or dropped tables in
  lock_tables() we notify caller and rely on that the caller will
  reopen tables.
parent 8b2b0e24

mysql-test/t/trigger.test

+113 −3
Original line number Diff line number Diff line
@@ -10,6 +10,11 @@ drop function if exists f1; 
drop procedure if exists p1;

--enable_warnings



# Create additional connections used through test

connect (addconroot1, localhost, root,,);

connect (addconroot2, localhost, root,,);

connection default;



create table t1 (i int);



# let us test some very simple trigger
@@ -680,12 +685,10 @@ end| 
delimiter ;|

update t1 set data = 1;



connect (addconroot, localhost, root,,);

connection addconroot;

connection addconroot1;

update t1 set data = 2;



connection default;

disconnect addconroot;

drop table t1;



#
@@ -765,3 +768,110 @@ insert into t1 values (3); 
select * from t1;

drop trigger t1_bi;

drop tables t1, t2;



# Tests for bug #12704 "Server crashes during trigger execution".

# If we run DML statements and CREATE TRIGGER statements concurrently

# it may happen that trigger will be created while DML statement is

# waiting for table lock. In this case we have to reopen tables and

# recalculate prelocking set.

# Unfortunately these tests rely on the order in which tables are locked

# by statement so they are non determenistic and are disabled.

--disable_parsing

create table t1 (id int);

create table t2 (id int);

create table t3 (id int);

create function f1() returns int return (select max(id)+2 from t2);

create view v1 as select f1() as f;



# Let us check that we notice trigger at all

connection addconroot1;

lock tables t2 write;

connection default;

send insert into t1 values ((select max(id) from t2)), (2);

--sleep 1

connection addconroot2;

create trigger t1_trg before insert on t1 for each row set NEW.id:= 1;

connection addconroot1;

unlock tables;

connection default;

reap;

select * from t1;



# Check that we properly calculate new prelocking set

insert into t2 values (3);

connection addconroot1;

lock tables t2 write;

connection default;

send insert into t1 values ((select max(id) from t2)), (4);

--sleep 1

connection addconroot2;

drop trigger t1_trg;

create trigger t1_trg before insert on t1 for each row

  insert into t3 values (new.id);

connection addconroot1;

unlock tables;

connection default;

reap;

select * from t1;

select * from t3;



# We should be able to do this even if fancy views are involved

connection addconroot1;

lock tables t2 write;

connection default;

send insert into t1 values ((select max(f) from v1)), (6);

--sleep 1

connection addconroot2;

drop trigger t1_trg;

create trigger t1_trg before insert on t1 for each row

  insert into t3 values (new.id + 100);

connection addconroot1;

unlock tables;

connection default;

reap;

select * from t1;

select * from t3;



# This also should work for multi-update

# Let us drop trigger to demonstrate that prelocking set is really

# rebuilt

drop trigger t1_trg;

connection addconroot1;

lock tables t2 write;

connection default;

send update t1, t2 set t1.id=10 where t1.id=t2.id;

--sleep 1

connection addconroot2;

create trigger t1_trg before update on t1 for each row

  insert into t3 values (new.id);

connection addconroot1;

unlock tables;

connection default;

reap;

select * from t1;

select * from t3;



# And even for multi-update converted from ordinary update thanks to view

drop view v1;

drop trigger t1_trg;

create view v1 as select t1.id as id1 from t1, t2 where t1.id= t2.id;

insert into t2 values (10);

connection addconroot1;

lock tables t2 write;

connection default;

send update v1 set id1= 11;

--sleep 1

connection addconroot2;

create trigger t1_trg before update on t1 for each row

  insert into t3 values (new.id + 100);

connection addconroot1;

unlock tables;

connection default;

reap;

select * from t1;

select * from t3;



drop function f1;

drop view v1;

drop table t1, t2, t3;

--enable_parsing

sql/lock.cc

+18 −3
Original line number Diff line number Diff line
@@ -93,23 +93,33 @@ static void print_lock_error(int error, const char *); 
    flags                       Options:

      MYSQL_LOCK_IGNORE_GLOBAL_READ_LOCK      Ignore a global read lock

      MYSQL_LOCK_IGNORE_FLUSH                 Ignore a flush tables.

      MYSQL_LOCK_NOTIFY_IF_NEED_REOPEN        Instead of reopening altered

                                              or dropped tables by itself,

                                              mysql_lock_tables() should

                                              notify upper level and rely

                                              on caller doing this.

    need_reopen                 Out parameter, TRUE if some tables were altered

                                or deleted and should be reopened by caller.



  RETURN

    A lock structure pointer on success.

    NULL on error.

    NULL on error or if some tables should be reopen.

*/



/* Map the return value of thr_lock to an error from errmsg.txt */

static int thr_lock_errno_to_mysql[]=

{ 0, 1, ER_LOCK_WAIT_TIMEOUT, ER_LOCK_DEADLOCK };



MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count, uint flags)

MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count,

                              uint flags, bool *need_reopen)

{

  MYSQL_LOCK *sql_lock;

  TABLE *write_lock_used;

  int rc;

  /* Map the return value of thr_lock to an error from errmsg.txt */

  DBUG_ENTER("mysql_lock_tables");



  *need_reopen= FALSE;



  for (;;)

  {

    if (!(sql_lock = get_lock_data(thd,tables,count, 0,&write_lock_used)))
@@ -178,6 +188,11 @@ MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **tables, uint count, uint flags) 
    thd->locked=0;

retry:

    sql_lock=0;

    if (flags & MYSQL_LOCK_NOTIFY_IF_NEED_REOPEN)

    {

      *need_reopen= TRUE;

      break;

    }

    if (wait_for_tables(thd))

      break;					// Couldn't open tables

  }

sql/mysql_priv.h

+5 −2
Original line number Diff line number Diff line
@@ -942,7 +942,7 @@ int open_tables(THD *thd, TABLE_LIST **tables, uint *counter, uint flags); 
int simple_open_n_lock_tables(THD *thd,TABLE_LIST *tables);

bool open_and_lock_tables(THD *thd,TABLE_LIST *tables);

bool open_normal_and_derived_tables(THD *thd, TABLE_LIST *tables, uint flags);

int lock_tables(THD *thd, TABLE_LIST *tables, uint counter);

int lock_tables(THD *thd, TABLE_LIST *tables, uint counter, bool *need_reopen);

TABLE *open_temporary_table(THD *thd, const char *path, const char *db,

			    const char *table_name, bool link_in_list);

bool rm_temporary_table(enum db_type base, char *path);
@@ -950,6 +950,7 @@ 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);

TABLE_LIST *find_table_in_list(TABLE_LIST *table,

                               uint offset_to_list,

                               const char *db_name,
@@ -1227,10 +1228,12 @@ extern pthread_t signal_thread; 
extern struct st_VioSSLAcceptorFd * ssl_acceptor_fd;

#endif /* HAVE_OPENSSL */



MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **table, uint count, uint flags);

MYSQL_LOCK *mysql_lock_tables(THD *thd, TABLE **table, uint count,

                              uint flags, bool *need_reopen);

/* mysql_lock_tables() flags bits */

#define MYSQL_LOCK_IGNORE_GLOBAL_READ_LOCK      0x0001

#define MYSQL_LOCK_IGNORE_FLUSH                 0x0002

#define MYSQL_LOCK_NOTIFY_IF_NEED_REOPEN        0x0004



void mysql_unlock_tables(THD *thd, MYSQL_LOCK *sql_lock);

void mysql_unlock_read_tables(THD *thd, MYSQL_LOCK *sql_lock);

sql/sp.cc

+61 −6
Original line number Diff line number Diff line
@@ -107,7 +107,7 @@ TABLE *open_proc_table_for_read(THD *thd, Open_tables_state *backup) 
{

  TABLE_LIST tables;

  TABLE *table;

  bool refresh;

  bool not_used;

  DBUG_ENTER("open_proc_table");



  /*
@@ -122,7 +122,7 @@ TABLE *open_proc_table_for_read(THD *thd, Open_tables_state *backup) 
  bzero((char*) &tables, sizeof(tables));

  tables.db= (char*) "mysql";

  tables.table_name= tables.alias= (char*)"proc";

  if (!(table= open_table(thd, &tables, thd->mem_root, &refresh,

  if (!(table= open_table(thd, &tables, thd->mem_root, &not_used,

                          MYSQL_LOCK_IGNORE_FLUSH)))

  {

    thd->restore_backup_open_tables_state(backup);
@@ -138,7 +138,7 @@ TABLE *open_proc_table_for_read(THD *thd, Open_tables_state *backup) 
    could lead to a deadlock if we have other tables opened.

  */

  if (!(thd->lock= mysql_lock_tables(thd, &table, 1,

                                     MYSQL_LOCK_IGNORE_FLUSH)))

                                     MYSQL_LOCK_IGNORE_FLUSH, &not_used)))

  {

    close_proc_table(thd, backup);

    DBUG_RETURN(0);
@@ -1265,7 +1265,8 @@ static bool add_used_routine(LEX *lex, Query_arena *arena, 




/*

  Add routine to the set of stored routines used by statement.

  Add routine which is explicitly used by statement to the set of stored

  routines used by this statement.



  SYNOPSIS

    sp_add_used_routine()
@@ -1276,7 +1277,8 @@ static bool add_used_routine(LEX *lex, Query_arena *arena, 
      rt_type - routine type (one of TYPE_ENUM_PROCEDURE/...)



  NOTES

    Will also add element to end of 'LEX::sroutines_list' list.

    Will also add element to end of 'LEX::sroutines_list' list (and will

    take into account that this is explicitly used routine).



    To be friendly towards prepared statements one should pass

    persistent arena as second argument.
@@ -1287,6 +1289,37 @@ void sp_add_used_routine(LEX *lex, Query_arena *arena, 
{

  rt->set_routine_type(rt_type);

  (void)add_used_routine(lex, arena, &rt->m_sroutines_key);

  lex->sroutines_list_own_last= lex->sroutines_list.next;

  lex->sroutines_list_own_elements= lex->sroutines_list.elements;

}





/*

  Remove routines which are only indirectly used by statement from

  the set of routines used by this statement.



  SYNOPSIS

    sp_remove_not_own_routines()

      lex  LEX representing statement

*/



void sp_remove_not_own_routines(LEX *lex)

{

  Sroutine_hash_entry *not_own_rt, *next_rt;

  for (not_own_rt= *(Sroutine_hash_entry **)lex->sroutines_list_own_last;

       not_own_rt; not_own_rt= next_rt)

  {

    /*

      It is safe to obtain not_own_rt->next after calling hash_delete() now

      but we want to be more future-proof.

    */

    next_rt= not_own_rt->next;

    hash_delete(&lex->sroutines, (byte *)not_own_rt);

  }



  *(Sroutine_hash_entry **)lex->sroutines_list_own_last= NULL;

  lex->sroutines_list.next= lex->sroutines_list_own_last;

  lex->sroutines_list.elements= lex->sroutines_list_own_elements;

}
@@ -1343,6 +1376,28 @@ static void sp_update_stmt_used_routines(THD *thd, LEX *lex, HASH *src) 
}





/*

  Add contents of list representing set of routines to the set of

  routines used by statement.



  SYNOPSIS

    sp_update_stmt_used_routines()

      thd  Thread context

      lex  LEX representing statement

      src  List representing set from which routines will be added



  NOTE

    It will also add elements to end of 'LEX::sroutines_list' list.

*/



static void sp_update_stmt_used_routines(THD *thd, LEX *lex, SQL_LIST *src)

{

  for (Sroutine_hash_entry *rt= (Sroutine_hash_entry *)src->first;

       rt; rt= rt->next)

    (void)add_used_routine(lex, thd->stmt_arena, &rt->key);

}





/*

  Cache sub-set of routines used by statement, add tables used by these

  routines to statement table list. Do the same for all routines used
@@ -1463,7 +1518,7 @@ sp_cache_routines_and_add_tables_for_view(THD *thd, LEX *lex, LEX *aux_lex) 
{

  Sroutine_hash_entry **last_cached_routine_ptr=

                          (Sroutine_hash_entry **)lex->sroutines_list.next;

  sp_update_stmt_used_routines(thd, lex, &aux_lex->sroutines);

  sp_update_stmt_used_routines(thd, lex, &aux_lex->sroutines_list);

  (void)sp_cache_routines_and_add_tables_aux(thd, lex, 

                                             *last_cached_routine_ptr, FALSE);

}

sql/sp.h

+1 −0
Original line number Diff line number Diff line
@@ -84,6 +84,7 @@ void sp_get_prelocking_info(THD *thd, bool *need_prelocking, 
                            bool *first_no_prelocking);

void sp_add_used_routine(LEX *lex, Query_arena *arena,

                         sp_name *rt, char rt_type);

void sp_remove_not_own_routines(LEX *lex);

void sp_update_sp_used_routines(HASH *dst, HASH *src);

bool sp_cache_routines_and_add_tables(THD *thd, LEX *lex, 

                                      bool first_no_prelock);