Re: Non-robustness in pmsignal.c

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Non-robustness in pmsignal.c
Date: 2022-10-08 17:44:41
Message-ID: 3658511.1665251081@sss.pgh.pa.us
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Andres Freund <andres(at)anarazel(dot)de> writes:
> When can PostmasterContext be NULL here, and why can we just continue without
> (re-)allocating PMChildInUse?

We'd only get into the !found stanza in a postmaster or a
standalone backend. A standalone backend isn't ever going to call
AssignPostmasterChildSlot or ReleasePostmasterChildSlot, so it
does not need the array; and it also doesn't have a PostmasterContext,
so there's not a good place to allocate the array either.

Perhaps there's a better way to distinguish am-I-a-postmaster,
but I thought checking PostmasterContext is fine since that ties
directly to what the code needs to do.

Yes, the code would malfunction if the PostmasterContext != NULL
condition changed from one cycle to the next, but that shouldn't
happen.

regards, tom lane

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