| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | Sami Imseih <samimseih(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Improve LWLock tranche name visibility across backends |
| Date: | 2025-08-26 00:14:40 |
| Message-ID: | aKz8cHo2oBr-6uq5@nathan |
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| Lists: | pgsql-hackers |
On Mon, Aug 25, 2025 at 04:59:41PM -0500, Sami Imseih wrote:
> hmm, can we really avoid a shared lock when reading from shared memory?
> considering access for both reads and writes can be concurrent to shared
> memory. We are also taking an exclusive lock when writing a new tranche.
We probably want to hold a lock while we 1) increment LWLockCounter and
copy a new tranche name to memory and 2) while we copy the current value of
LWLockCounter to our backend-local variable. Otherwise, AFAICT we don't
need one. We could probably use ShmemLock for this.
--
nathan
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