Re: VM corruption on standby

On Mon, 18 Aug 2025 at 13:15, I wrote:
> > I do not like this patch one bit: it will replace one set of problems
> > with another set, namely systems that fail to shut down.
>
> I did not observe this during my by-hand testing.

I am sorry: I was wrong. This is exactly what happens in this test
(modified 001_multixact.pl).
To be precise, after the INSERT process exits, CHECKPOINT process
waits indefinitely in LWLockAcquire.

It looks like the reason why proc_exit(1) releases all holded lwlocks
is because we use it to notify all lwlock contenders through shared
memory about state change, which will not be notified otherwise, since
we do not check for signals inside LWLockAcquire.

Looks like we need to do something like ConditionVariableBroadcast(),
but without lwlock release, to notify all lwlock contenders and then
exit(2).

===
As for the fix, I am now trying to make attached work. The idea to
"escalate" proc_exit to immediately exit via syscall comes to my mind
from how elog(ERROR) behaves in CRIT sections (every elog(ERROR)
efficiently becomes elog(PANIC)).

-- 
Best regards,
Kirill Reshke