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From: Heikki Linnakangas <[email protected]>
To: Robert Haas <[email protected]>
To: Michael Paquier <[email protected]>
Cc: Postgres hackers <[email protected]>
Cc: Andrey Borodin <[email protected]>
Subject: Re: injection_points: Switch wait/wakeup to use atomics rather than latches
Date: Fri, 29 May 2026 16:31:39 +0300
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+TgmoYE-9WhM-owWtX3grbSeHtOJCF__wEEdoD-jj-oJ+=TSg@mail.gmail.com>
References: <[email protected]>
	<CA+TgmoamSXmT7uMXBw6c3YJgSSz6dYdpMsJf47jwaPH9kVbmyA@mail.gmail.com>
	<[email protected]>
	<CA+TgmoYE-9WhM-owWtX3grbSeHtOJCF__wEEdoD-jj-oJ+=TSg@mail.gmail.com>

On 29/05/2026 15:48, Robert Haas wrote:
> On Thu, May 28, 2026 at 7:19 PM Michael Paquier <[email protected]> wrote:
>> On Thu, May 28, 2026 at 08:40:39AM -0400, Robert Haas wrote:
>>> After reading this email, the linked-to email, and the commit message
>>> for the patch, I still don't have a clear understanding of what this
>>> is intended to fix. It seems like it's going to make the
>>> responsiveness worse. In general, we want to replace escalating wait
>>> loops with things that wake up instantly at the right time, and this
>>> is going in the opposite direction.
>>
>> This is an exchange between responsiveness of the system and
>> flexibility.  I have had two complaints in the past about the fact
>> that the waits and wakeups were not doable due to the fact that we
>> rely on condition variables and latches:
> 
> I'm still struggling to understand. Condition variables and latches
> are both designed to allow for nice waits and wakeups.

They only work after you have a PGPROC slot. If you want to inject code 
to authentication, or into postmaster, you cannot use them.

- Heikki

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