Re: Code paths where LWLock should be released on failure

On Thu, Apr 23, 2015 at 2:46 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
>> After looking at bug #13128, I have been looking at the code around
>> LWLockAcquire/Release to see if there are similar issues elsewhere.
>> Here are my findings:
>
> IIRC, we automatically release all LWLocks at the start of error recovery,
> so I rather doubt that any of this is necessary.

Perhaps this is purely cosmetic for most those code, but not all... if
you have a look at #13128, not releasing TwoPhaseStateLock causes a
deadlock on startup when max_prepared_transactions does not have
enough slots. I have also been surprised by the inconsistencies
particularly in predicate.c or other places regarding LWLock releases.
Sometimes they are released on failure, sometimes not.
Regards,
--
Michael