Horton

Re: race condition in pg_class

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Smolkin Grigory <smallkeen@gmail.com>, pgsql-hackers@postgresql.org
Date: 2024-05-13T18:54:03Z
Lists: pgsql-hackers

Commits

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

  1. Replace tests of ALTER DATABASE RESET TABLESPACE.

  2. meson: Flush stdout in testwrap

  3. Fix catcache invalidation of a list entry that's being built

  4. Stop reading uninitialized memory in heap_inplace_lock().

  5. Fix use of uninitialized value in previous commit.

  6. Back-patch "Refactor code in tablecmds.c to check and process tablespace moves"

  7. Fix data loss at inplace update after heap_update().

  8. For inplace update durability, make heap_update() callers wait.

  9. Warn if LOCKTAG_TUPLE is held at commit, under debug_assertions.

  10. Don't lose partitioned table reltuples=0 after relhassubclass=f.

  11. Fix new assertion for MERGE view_name ... DO NOTHING.

  12. Remove configuration-dependent output from new inplace-inval test.

  13. AccessExclusiveLock new relations just after assigning the OID.

  14. Cope with inplace update making catcache stale during TOAST fetch.

  15. Expand comments and add an assertion in nodeModifyTable.c.

  16. Improve test coverage for changes to inplace-updated catalogs.

  17. Lock before setting relhassubclass on RELKIND_PARTITIONED_INDEX.

  18. Lock owned sequences during ALTER TABLE SET { LOGGED | UNLOGGED }.

  19. Make TAP todo_start effects the same under Meson and prove_check.

  20. Add an injection_points isolation test suite.

  21. Add wait event type "InjectionPoint", a custom type like "Extension".

  22. Create waitfuncs.c for pg_isolation_test_session_is_blocked().

  23. Rework planning and execution of UPDATE and DELETE.

On Mon, May 13, 2024 at 04:59:59PM +0900, Michael Paquier wrote:
> About inplace050-tests-inj-v1.patch.
> 
> +	/* Check if blocked_pid is in injection_wait(). */
> +	proc = BackendPidGetProc(blocked_pid);
> +	if (proc == NULL)
> +		PG_RETURN_BOOL(false);	/* session gone: definitely unblocked */
> +	wait_event =
> +		pgstat_get_wait_event(UINT32_ACCESS_ONCE(proc->wait_event_info));
> +	if (wait_event && strncmp("INJECTION_POINT(",
> +							  wait_event,
> +							  strlen("INJECTION_POINT(")) == 0)
> +		PG_RETURN_BOOL(true);
> 
> Hmm.  I am not sure that this is the right interface for the job
> because this is not only related to injection points but to the
> monitoring of a one or more wait events when running a permutation
> step.

Could you say more about that?  Permutation steps don't monitor wait events
today.  This patch would be the first instance of that.

> Perhaps this is something that should be linked to the spec
> files with some property area listing the wait events we're expected
> to wait on instead when running a step that we know will wait?

The spec syntax doesn't distinguish contention types at all.  The isolation
tester's needs are limited to distinguishing:

  (a) process is waiting on another test session
  (b) process is waiting on automatic background activity (autovacuum, mainly)

Automatic background activity doesn't make a process enter or leave
injection_wait(), so all injection point wait events fall in (a).  (The tester
ignores (b), since those clear up without intervention.  Failing to ignore
them, as the tester did long ago, made output unstable.)