Re: BUG #3245: PANIC: failed to re-find shared loc k o b j ect

Tom Lane wrote:
> Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
>> Locking the same lock twice is usually handled correctly, I don't
>> understand why it fails in this case. I'm thinking that the locallock
>> structs somehow get out of sync with the lock structs in shared memory.
>> The twophase-records are created from the locallock structs alone, so if
>> there's extra entries in the locallocks table for some reason, we'd get
>> the symptoms we have.
>
> Hmm. I was just noticing this comment in PostPrepare_Locks:
>
> * We do this separately because we may have multiple locallock entries
> * pointing to the same proclock, and we daren't end up with any dangling
> * pointers.
>
> I'm not clear at the moment on why such a state would exist, but could
> it be related?

That caught my eye as well. I'm not sure what the other alternative
would be, that might leave dangling pointers. The comment seems to be
copy-pasted from LockReleaseAll.

>> Unless you have a better idea, I'd like to add some more debug-prints to
>> AtPrepare_Locks to see what gets written to the state file and why.
>
> Seems like a reasonable thing to pursue.

Dave, would you please create a new binary with the attached patch? And
LOCK_DEBUG and assertions and debug enabled.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com