Message-ID: <da3df015-2c53-424f-aec7-dfeca60f5f5f@iki.fi>
Date: Wed, 10 Jan 2024 23:25:42 +0200
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Subject: Re: Stack overflow issue
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To: Robert Haas <robertmhaas@gmail.com>
Cc: Egor Chindyaskin <kyzevan23@mail.ru>, Sascha Kuhl
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From: Heikki Linnakangas <hlinnaka@iki.fi>
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On 05/01/2024 19:23, Robert Haas wrote:
> On Fri, Nov 24, 2023 at 10:47 AM Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>> What do you think?
> 
> At least for 0001 and 0002, I think we should just add the stack depth checks.
> 
> With regard to 0001, CommitTransactionCommand() and friends are hard
> enough to understand as it is; they need "goto" like I need an extra
> hole in my head.
> 
> With regard to 0002, this function isn't sufficiently important to
> justify adding special-case code for an extremely rare event. We
> should just handle it the way we do in general.
> 
> I agree that in the memory-context case it might be worth expending
> some more code to be more clever. But I probably wouldn't do that for
> MemoryContextStats(); check_stack_depth() seems fine for that one.
> 
> In general, I think we should try to keep the number of places that
> handle stack overflow in "special" ways as small as possible.

The problem with CommitTransactionCommand (or rather 
AbortCurrentTransaction() which has the same problem)
and ShowTransactionStateRec is that they get called in a state where 
aborting can lead to a panic. If you add a "check_stack_depth()" to them 
and try to reproducer scripts that Egor posted, you still get a panic.

I'm not sure if MemoryContextStats() could safely elog(ERROR). But at 
least it would mask the "out of memory" that caused the stats to be 
printed in the first place.

-- 
Heikki Linnakangas
Neon (https://neon.tech)