Thread

Re: injection_points: Switch wait/wakeup to use atomics rather than latches

Heikki Linnakangas <hlinnaka@iki.fi> — 2026-05-29T13:31:39Z

On 29/05/2026 15:48, Robert Haas wrote:
> On Thu, May 28, 2026 at 7:19 PM Michael Paquier <michael@paquier.xyz> 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