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From: Alexander Korotkov <[email protected]>
To: Tom Lane <[email protected]>
Cc: Alexander Lakhin <[email protected]>
Cc: [email protected]
Subject: Re: BUG #18374: Printing memory contexts on OOM condition might lead to segmentation fault
Date: Wed, 6 Mar 2024 22:24:03 +0200
Message-ID: <CAPpHfduPAmF95Zg=sMfhBW+0Q=Bq2KKzF7AamvTQ0UDm80ZOLA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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On Sun, Mar 3, 2024 at 11:39 PM Tom Lane <[email protected]> wrote:
>> I do think it's probably worth reducing MemoryContextDelete's stack
> usage to O(1), just to ensure we can't get into stack trouble during
> transaction abort.  That's not hard at all, as attached.
>
> I tried to make MemoryContextResetChildren work similarly, but that
> doesn't work because if we're not removing child contexts then we
> need extra state to tell which ones we've done already.  For the
> same reason my idea for bounding the stack space needed by
> MemoryContextStats doesn't seem to work.  We could possibly make it
> work if we were willing to add a temporary-use pointer field to all
> MemoryContext headers, but I'm unconvinced that'd be a good tradeoff.

For removing recursion from memory context processing, please check
the patch by Heikki [1], and my slightly revised version [2].

Links.
1. https://www.postgresql.org/message-id/6b48c746-9704-46dc-b9be-01fe4137c824%40iki.fi
2. https://www.postgresql.org/message-id/CAPpHfdtQVzkKgrxqKZE9yESnu7cAATVQbGktVOSXPNWG7GOkhA%40mail.gma...

------
Regards,
Alexander Korotkov

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