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dfa2acb141
Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
66 lines
2.7 KiB
Text
66 lines
2.7 KiB
Text
#
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# Test for bug #45143 "All connections hang on concurrent ALTER TABLE".
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#
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# Concurrent execution of statements which required weak write lock
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# (TL_WRITE_ALLOW_WRITE) on several instances of the same table and
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# statements which tried to acquire stronger write lock (TL_WRITE,
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# TL_WRITE_ALLOW_READ) on this table might have led to deadlock.
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drop table if exists t1;
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# Create auxiliary connections used through the test.
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# Reset DEBUG_SYNC facility before using it.
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set debug_sync= 'RESET';
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# Turn off logging so calls to locking subsystem performed
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# for general_log table won't interfere with our test.
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set @old_general_log = @@global.general_log;
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set @@global.general_log= OFF;
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create table t1 (i int) engine=InnoDB;
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insert into t1 values (1);
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# Prepare user lock which will be used for resuming execution of
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# the first statement after it acquires TL_WRITE_ALLOW_WRITE lock.
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select get_lock("lock_bug45143_wait", 0);
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get_lock("lock_bug45143_wait", 0)
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1
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# Switch to connection 'con_bug45143_1'.
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# Sending:
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insert into t1 values (get_lock("lock_bug45143_wait", 100));;
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# Switch to connection 'con_bug45143_2'.
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# Wait until the above INSERT takes TL_WRITE_ALLOW_WRITE lock on 't1'
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# and then gets blocked on user lock 'lock_bug45143_wait'.
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# Ensure that upcoming SELECT waits after acquiring TL_WRITE_ALLOW_WRITE
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# lock for the first instance of 't1'.
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set debug_sync='thr_multi_lock_after_thr_lock SIGNAL parked WAIT_FOR go';
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# Sending:
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select count(*) > 0 from t1 as a, t1 as b for update;;
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# Switch to connection 'con_bug45143_3'.
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# Wait until the above SELECT ... FOR UPDATE is blocked after
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# acquiring lock for the the first instance of 't1'.
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set debug_sync= 'now WAIT_FOR parked';
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# Send LOCK TABLE statement which will try to get TL_WRITE lock on 't1':
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lock table t1 write;;
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# Switch to connection 'default'.
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# Wait until this LOCK TABLES statement starts waiting for table lock.
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# Allow SELECT ... FOR UPDATE to resume.
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# Since it already has TL_WRITE_ALLOW_WRITE lock on the first instance
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# of 't1' it should be able to get lock on the second instance without
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# waiting, even although there is another thread which has such lock
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# on this table and also there is a thread waiting for a TL_WRITE on it.
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set debug_sync= 'now SIGNAL go';
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# Switch to connection 'con_bug45143_2'.
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# Reap SELECT ... FOR UPDATE
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count(*) > 0
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1
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# Switch to connection 'default'.
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# Resume execution of the INSERT statement.
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select release_lock("lock_bug45143_wait");
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release_lock("lock_bug45143_wait")
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1
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# Switch to connection 'con_bug45143_1'.
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# Reap INSERT statement.
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# Switch to connection 'con_bug45143_3'.
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# Reap LOCK TABLES statement.
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unlock tables;
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# Switch to connection 'default'.
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# Do clean-up.
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set debug_sync= 'RESET';
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set @@global.general_log= @old_general_log;
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drop table t1;
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