Re: Assertion failure in SnapBuildInitialSnapshot()

Amit Kapila <amit.kapila16@gmail.com>

From: Amit Kapila <amit.kapila16@gmail.com>

To: Masahiko Sawada <sawada.mshk@gmail.com>

Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Thomas Munro <thomas.munro@gmail.com>

Date: 2023-02-07T11:19:50Z

Lists: pgsql-hackers

On Tue, Jan 31, 2023 at 6:08 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> Attached updated patches.
>

In back-branch patches, the change is as below:
+ *
+ * NB: the caller must hold ProcArrayLock in an exclusive mode regardless of
+ * already_locked which is unused now but kept for ABI compatibility.
  */
 void
 ProcArraySetReplicationSlotXmin(TransactionId xmin, TransactionId catalog_xmin,
  bool already_locked)
 {
- Assert(!already_locked || LWLockHeldByMe(ProcArrayLock));
-
- if (!already_locked)
- LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+ Assert(LWLockHeldByMeInMode(ProcArrayLock, LW_EXCLUSIVE));

This change looks odd to me. I think it would be better to pass
'already_locked' as true from the caller.

-- 
With Regards,
Amit Kapila.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

Fix a race condition in updating procArray->replication_slot_xmin.
- 2a5225b99d76 19 (unreleased) landed
- fd7c86cfaf13 18.2 landed
- 123b851abdac 17.8 landed
- 82146672261d 16.12 landed
- fa557d3005e7 15.16 landed
- 57048d6e1733 14.21 landed
Don't retreat slot's confirmed_flush LSN.
- ad5eaf390c58 18.0 cited
Add additional checks while creating the initial decoding snapshot.
- 240e0dbacd39 16.0 landed