#
# Test for bug #45143 "All connections hang on concurrent ALTER TABLE".
#
# Concurrent execution of statements which required weak write lock
# (TL_WRITE_ALLOW_WRITE) on several instances of the same table and
# statements which tried to acquire stronger write lock (TL_WRITE,
# TL_WRITE_ALLOW_READ) on this table might have led to deadlock.
drop table if exists t1;
# Create auxiliary connections used through the test.
# Reset DEBUG_SYNC facility before using it.
set debug_sync= 'RESET';
# Turn off logging so calls to locking subsystem performed
# for general_log table won't interfere with our test.
set @old_general_log = @@global.general_log;
set @@global.general_log= OFF;
create table t1 (i int) engine=InnoDB;
insert into t1 values (1);
# Prepare user lock which will be used for resuming execution of
# the first statement after it acquires TL_WRITE_ALLOW_WRITE lock.
select get_lock("lock_bug45143_wait", 0);
get_lock("lock_bug45143_wait", 0)
1
# Switch to connection 'con_bug45143_1'.
# Sending:
insert into t1 values (get_lock("lock_bug45143_wait", 100));;
# Switch to connection 'con_bug45143_2'.
# Wait until the above INSERT takes TL_WRITE_ALLOW_WRITE lock on 't1'
# and then gets blocked on user lock 'lock_bug45143_wait'.
# Ensure that upcoming SELECT waits after acquiring TL_WRITE_ALLOW_WRITE
# lock for the first instance of 't1'.
set debug_sync='thr_multi_lock_after_thr_lock SIGNAL parked WAIT_FOR go';
# Sending:
select count(*) > 0 from t1 as a, t1 as b for update;;
# Switch to connection 'con_bug45143_3'.
# Wait until the above SELECT ... FOR UPDATE is blocked after
# acquiring lock for the the first instance of 't1'.
set debug_sync= 'now WAIT_FOR parked';
# Send LOCK TABLE statement which will try to get TL_WRITE lock on 't1':
lock table t1 write;;
# Switch to connection 'default'.
# Wait until this LOCK TABLES statement starts waiting for table lock.
# Allow SELECT ... FOR UPDATE to resume.
# Since it already has TL_WRITE_ALLOW_WRITE lock on the first instance
# of 't1' it should be able to get lock on the second instance without
# waiting, even although there is another thread which has such lock
# on this table and also there is a thread waiting for a TL_WRITE on it.
set debug_sync= 'now SIGNAL go';
# Switch to connection 'con_bug45143_2'.
# Reap SELECT ... FOR UPDATE
count(*) > 0
1
# Switch to connection 'default'.
# Resume execution of the INSERT statement.
select release_lock("lock_bug45143_wait");
release_lock("lock_bug45143_wait")
1
# Switch to connection 'con_bug45143_1'.
# Reap INSERT statement.
# Switch to connection 'con_bug45143_3'.
# Reap LOCK TABLES statement.
unlock tables;
# Switch to connection 'default'.
# Do clean-up.
set debug_sync= 'RESET';
set @@global.general_log= @old_general_log;
drop table t1;