Re: Refine comments on usage WL_POSTMASTER_DEATH vs WL_EXIT_ON_PM_DEATH

Hi, Heikki!

On Wed, 23 Oct 2024 at 21:00, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:

> On 23/10/2024 12:18, Pavel Borisov wrote:
> > Hi, Hackers!
> >
> > Current comments on the usage of WL_POSTMASTER_DEATH state that it
> > should be used for scenarios of finishing other than immediately i.e.
> > returning values and waiting for postmaster dies.
> > In fact, in parts of the code, it's currently used to immediately exit
> > or throw FATAL (in the walsender and in libpq).
> >
> > So I propose change the comments on WL_POSTMASTER_DEATH stating that it
> > could be used for both cases: for processing and setting return values
> > if that's needed, and for immediate exit otherwise.
>
> I see what you mean, but I don't think the proposed patch is making it
> better. With WL_POSTMASTER_DEATH, the WaitLatch call returns if the
> postmaster dies. What the caller does then is the caller's business.
> That's different from WL_EXIT_ON_PM_DEATH in that with
> WL_EXIT_ON_PM_DEATH, WaitLatch itself will do the exit(), not the caller.
>

That was exactly my point. Actually the caller should not wait, it could do
whatever it wants contrary to the existing comments:
> WL_POSTMASTER_DEATH: Wait for postmaster to die

I don't insist on this patch, but existing comments on this look somewhat
misleading.

Regards,
Pavel Borisov