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From: Bossart, Nathan <bossartn@amazon.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Andres Freund <andres@anarazel.de>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: sulamul@gmail.com <sulamul@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: inefficient loop in StandbyReleaseLockList()
Date: Mon, 1 Nov 2021 16:00:54 +0000
Message-ID: <8D394A05-1B89-42DD-96F3-BCF41016EEC7@amazon.com> (raw)
In-Reply-To: <1013797.1635709095@sss.pgh.pa.us>
References: <CD2F0E7F-9822-45EC-A411-AE56F14DEA9F@amazon.com>
	<CAAJ_b94_awY-VfbLbzxm4zNni3NXxG3wrSkSgnHyCDqHnT+eJg@mail.gmail.com>
	<20211028.155751.1898631306946946681.horikyota.ntt@gmail.com>
	<20211028220748.6ekrl74minwq75f4@alap3.anarazel.de>
	<20211028221424.6wtcse3qkbf2cmqo@alap3.anarazel.de>
	<560364.1635459891@sss.pgh.pa.us>
	<B4C04240-1AAC-4200-9636-BCC7984688D8@amazon.com>
	<565036.1635463448@sss.pgh.pa.us>
	<20211028235248.4kbhtcqn2hvjukbd@alap3.anarazel.de>
	<YXuaLlYJxkmwnTDl@paquier.xyz>
	<0108A03D-FF2B-4CBC-933B-E047CD975158@amazon.com>
	<1013797.1635709095@sss.pgh.pa.us>

On 10/31/21, 12:39 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:
> Yeah, there's no expectation that this data structure needs to be kept
> consistent after an error; and I'm not real sure that the existing
> code could claim to satisfy such a requirement if we did need it.
> (There's at least a short window where the caller's hash table entry
> will point at an already-freed List.)

Right.

> Pushed the patch as given.  I've not yet reviewed other list_delete_first
> callers, but I'll take a look.  (I seem to remember that I did survey
> them while writing 1cff1b95a, but I evidently missed that this code
> could be dealing with a list long enough to be problematic.)

Thanks!

Nathan



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