Commit 1c2a13b8 authored by unknown's avatar unknown
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Bug#16986 - Deadlock condition with MyISAM tables 

Addendum fixes after changing the condition variable
for the global read lock.

The stress test suite revealed some deadlocks. Some were
related to the new condition variable (COND_global_read_lock)
and some were general problems with the global read lock.

It is now necessary to signal COND_global_read_lock whenever 
COND_refresh is signalled.

We need to wait for the release of a global read lock if one 
is set before every operation that requires a write lock.
But we must not wait if we have locked tables by LOCK TABLES.
After setting a global read lock a thread waits until all
write locks are released.


mysql-test/r/lock_multi.result:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Added test results.
mysql-test/t/lock_multi.test:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Added tests for possible deadlocks that did not occur
  with the stress test suite.
mysys/thr_lock.c:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Added a protection against an infinite loop that occurs
  with the test case for Bug #20662.
sql/lock.cc:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Signal COND_global_read_lock whenever COND_refresh
  is signalled by using the new function broadcast_refresh().
  Added the definition of a new function that signals 
  COND_global_read_lock whenever COND_refresh is signalled.
sql/mysql_priv.h:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Added a declaration for a new function that signals 
  COND_global_read_lock whenever COND_refresh is signalled.
sql/sql_base.cc:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Signal COND_global_read_lock whenever COND_refresh
  is signalled by using the new function broadcast_refresh().
sql/sql_handler.cc:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Signal COND_global_read_lock whenever COND_refresh
  is signalled by using the new function broadcast_refresh().
sql/sql_insert.cc:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Removed global read lock handling from inside of 
  INSERT DELAYED. It is handled on a higher level now.
sql/sql_parse.cc:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Wait for the release of a global read lock if one is set
  before every operation that requires a write lock.
  But don't wait if locked tables exist already.
sql/sql_table.cc:
  Bug#16986 - Deadlock condition with MyISAM tables
  Addendum fixes after changing the condition variable
  for the global read lock.
  Removed global read lock handling from inside of 
  CREATE TABLE. It is handled on a higher level now.
  Signal COND_global_read_lock whenever COND_refresh
  is signalled by using the new function broadcast_refresh().
parent 41b9884d

mysql-test/r/lock_multi.result

+15 −0
Original line number Diff line number Diff line
@@ -67,6 +67,21 @@ Select_priv 
N

use test;

use test;

CREATE TABLE t1 (c1 int);

LOCK TABLE t1 WRITE;

 FLUSH TABLES WITH READ LOCK;

CREATE TABLE t2 (c1 int);

UNLOCK TABLES;

UNLOCK TABLES;

DROP TABLE t1, t2;

CREATE TABLE t1 (c1 int);

LOCK TABLE t1 WRITE;

 FLUSH TABLES WITH READ LOCK;

CREATE TABLE t2 AS SELECT * FROM t1;

ERROR HY000: Table 't2' was not locked with LOCK TABLES

UNLOCK TABLES;

UNLOCK TABLES;

DROP TABLE t1;

create table t1 (f1 int(12) unsigned not null auto_increment, primary key(f1)) engine=innodb;

lock tables t1 write;

 alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; alter table t1 auto_increment=0; //

mysql-test/t/lock_multi.test

+50 −0
Original line number Diff line number Diff line
@@ -142,6 +142,7 @@ disconnect con2; 
--error ER_DB_DROP_EXISTS

DROP DATABASE mysqltest_1;



#

# Bug#16986 - Deadlock condition with MyISAM tables

#

connection locker;
@@ -170,6 +171,55 @@ connection locker; 
use test;

#

connection default;

#

# Test if CREATE TABLE with LOCK TABLE deadlocks.

#

connection writer;

CREATE TABLE t1 (c1 int);

LOCK TABLE t1 WRITE;

#

# This waits until t1 is unlocked.

connection locker;

send FLUSH TABLES WITH READ LOCK;

--sleep 1

#

# This must not block.

connection writer;

CREATE TABLE t2 (c1 int);

UNLOCK TABLES;

#

# This awakes now.

connection locker;

reap;

UNLOCK TABLES;

#

connection default;

DROP TABLE t1, t2;

#

# Test if CREATE TABLE SELECT with LOCK TABLE deadlocks.

#

connection writer;

CREATE TABLE t1 (c1 int);

LOCK TABLE t1 WRITE;

#

# This waits until t1 is unlocked.

connection locker;

send FLUSH TABLES WITH READ LOCK;

--sleep 1

#

# This must not block.

connection writer;

--error 1100

CREATE TABLE t2 AS SELECT * FROM t1;

UNLOCK TABLES;

#

# This awakes now.

connection locker;

reap;

UNLOCK TABLES;

#

connection default;

DROP TABLE t1;



#

# Bug #17264: MySQL Server freeze

mysys/thr_lock.c

+2 −0
Original line number Diff line number Diff line
@@ -204,6 +204,8 @@ static void check_locks(THR_LOCK *lock, const char *where, 
      {

	if ((int) data->type == (int) TL_READ_NO_INSERT)

	  count++;

        /* Protect against infinite loop. */

        DBUG_ASSERT(count <= lock->read_no_write_count);

      }

      if (count != lock->read_no_write_count)

      {

sql/lock.cc

+39 −5
Original line number Diff line number Diff line
@@ -905,7 +905,7 @@ void unlock_table_name(THD *thd, TABLE_LIST *table_list) 
  if (table_list->table)

  {

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

    (void) pthread_cond_broadcast(&COND_refresh);

    broadcast_refresh();

  }

}
@@ -997,9 +997,9 @@ bool lock_table_names(THD *thd, TABLE_LIST *table_list) 
			(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

    One must have a lock on LOCK_open when calling this.

    This function will broadcast refresh signals to inform other threads

    that the name locks are removed.



  RETURN

    0	ok
@@ -1013,7 +1013,7 @@ void unlock_table_names(THD *thd, TABLE_LIST *table_list, 
       table != last_table;

       table= table->next_local)

    unlock_table_name(thd,table);

  pthread_cond_broadcast(&COND_refresh);

  broadcast_refresh();

}
@@ -1304,3 +1304,37 @@ bool make_global_read_lock_block_commit(THD *thd) 
}





/*

  Broadcast COND_refresh and COND_global_read_lock.



  SYNOPSIS

    broadcast_refresh()

      void                      No parameters.



  DESCRIPTION

    Due to a bug in a threading library it could happen that a signal

    did not reach its target. A condition for this was that the same

    condition variable was used with different mutexes in

    pthread_cond_wait(). Some time ago we changed LOCK_open to

    LOCK_global_read_lock in global read lock handling. So COND_refresh

    was used with LOCK_open and LOCK_global_read_lock.



    We did now also change from COND_refresh to COND_global_read_lock

    in global read lock handling. But now it is necessary to signal

    both conditions at the same time.



  NOTE

    When signalling COND_global_read_lock within the global read lock

    handling, it is not necessary to also signal COND_refresh.



  RETURN

    void

*/



void broadcast_refresh(void)

{

  VOID(pthread_cond_broadcast(&COND_refresh));

  VOID(pthread_cond_broadcast(&COND_global_read_lock));

}

sql/mysql_priv.h

+1 −0
Original line number Diff line number Diff line
@@ -1342,6 +1342,7 @@ void start_waiting_global_read_lock(THD *thd); 
bool make_global_read_lock_block_commit(THD *thd);

bool set_protect_against_global_read_lock(void);

void unset_protect_against_global_read_lock(void);

void broadcast_refresh(void);



/* Lock based on name */

int lock_and_wait_for_table_name(THD *thd, TABLE_LIST *table_list);