Re: Assertion failure in SnapBuildInitialSnapshot()

On Mon, Jan 30, 2023 at 8:30 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Fri, Jan 27, 2023 at 4:31 PM Hayato Kuroda (Fujitsu)
> <kuroda.hayato@fujitsu.com> wrote:
> >
> > Thank you for making the patch! I'm still considering whether this approach is
> > correct, but I can put a comment to your patch anyway.
> >
> > ```
> > -       Assert(!already_locked || LWLockHeldByMe(ProcArrayLock));
> > -
> > -       if (!already_locked)
> > -               LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
> > +       Assert(LWLockHeldByMe(ProcArrayLock));
> > ```
> >
> > In this function, we regard that the ProcArrayLock has been already acquired as
> > exclusive mode and modify data. I think LWLockHeldByMeInMode() should be used
> > instead of LWLockHeldByMe().
> >
>
> Right, this is even evident from the comments atop
> ReplicationSlotsComputeRequiredXmin("If already_locked is true,
> ProcArrayLock has already been acquired exclusively.".

Agreed, will fix in the next version patch.

> But, I am not
> sure if it is a good idea to remove 'already_locked' parameter,
> especially in back branches as this is an exposed API.

Yes, we should not remove the already_locked parameter in
backbranches. So I was thinking of keeping it on back branches.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com