Horton

Re: Improve LWLock tranche name visibility across backends

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Sami Imseih <samimseih@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Rahila Syed <rahilasyed90@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-08-29T16:02:02Z
Lists: pgsql-hackers 
On Thu, Aug 28, 2025 at 05:53:23PM -0500, Sami Imseih wrote:
>> I think this patch set will require reworking the "GetNamedLWLockTranche
>> crashes on Windows in normal backend" patch [0], but AFAICT we can easily
>> adjust it to scan through NamedLWLockTrancheNames instead.
> 
> Except, we will need to turn the char**NamedLWLockTranche into a struct
> that will hold the num_lwlocks as well. Something like. But that is doable.

Ah, right.

> If there is no interest to backpatch [0], maybe we should just make this
> change as part of this patch set. What do you think? I can make this change
> in v18.

I think we should keep that separate.  I don't see any benefit to combining
it, and it'd be good to keep the discussion in a single thread in the
archives for future reference.

-- 
nathan

Commits

  1. test_dsa: Avoid leaking LWLock tranches.

  2. Teach DSM registry to ERROR if attaching to an uninitialized entry.

  3. Add a test harness for the LWLock tranche code.

  4. Revert recent change to RequestNamedLWLockTranche().

  5. Move dynamically-allocated LWLock tranche names to shared memory.

  6. Prepare DSM registry for upcoming changes to LWLock tranche names.

  7. Add GetNamedDSA() and GetNamedDSHash().