Thread: Is it possible that session lock is not released

Is it possible that session lock is not released

From

Date:

12 December 2013, 03:57:06

Hi,
    I just found that ShutdownPostgres() only releases USER_LOCKMETHOD locks, so why not
release DEFAULT_LOCKMETHOD locks? Check if this is possible:
    We are doing a CREATE INDEX CONCURRENTLY, and codes runs to

    LockRelationIdForSession(&heaprelid, ShareUpdateExclusiveLock);

    PopActiveSnapshot();
    CommitTransactionCommand();

Now transaction goes to default state, then this backend is killed or some FATAL error happens,
AbortOutOfAnyTransaction() in ShutdownPostgres() will do nothing since transaction is in default
state, and session lock on heaprelid is still held after ShutdownPostgres(), so subsequent operations
could be blocked by this session lock.

Thanks.

Re: Is it possible that session lock is not released

From

Tom Lane

Date:

12 December 2013, 04:12:42

T <kurt023@hotmail.com> writes:
> Now transaction goes to default state, then this backend is killed or some FATAL error happens,
> AbortOutOfAnyTransaction() in ShutdownPostgres() will do nothing since transaction is in default
> state, and session lock on heaprelid is still held after  ShutdownPostgres(), so subsequent operations
> could be blocked by this session lock.

This would only be an issue if we were to accept interrupts between the
CommitTransactionCommand() and StartTransactionCommand() steps ... which
we don't.  I'll admit it's a tad on the fragile side but I don't see a
bug.

            regards, tom lane