Horton

Re: Clean up NamedLWLockTranche stuff

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Sami Imseih <samimseih@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>, Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2026-03-27T21:22:33Z
Lists: pgsql-hackers 
Hi,

On 2026-03-27 11:45:56 +0200, Heikki Linnakangas wrote:
> Committed with that little change, thanks!

This seems to have broken buildfarm animal batta:

https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=batta&dt=2026-03-27%2002%3A05%3A01

# Running: pg_rewind --debug --source-pgdata /home/admin/batta/buildroot/HEAD/pgsql.build/src/bin/pg_rewind/tmp_check/t_001_basic_standby_local_data/pgdata --target-pgdata /home/admin/batta/buildroot/HEAD/pgsql.build/src/bin/pg_rewind/tmp_check/t_001_basic_primary_local_data/pgdata --no-sync --config-file /home/admin/batta/buildroot/HEAD/pgsql.build/src/bin/pg_rewind/tmp_check/tmp_test_QbsG/primary-postgresql.conf.tmp
pg_rewind: executing "/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres" for target server to complete crash recovery
TRAP: failed Assert("MemoryContextIsValid(context)"), File: "mcxt.c", Line: 1270, PID: 230491
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(ExceptionalCondition+0x54)[0xaaaae186c204]
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(MemoryContextAllocExtended+0x0)[0xaaaae18a2a24]
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(RequestNamedLWLockTranche+0x6c)[0xaaaae16e7310]
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(process_shmem_requests+0x28)[0xaaaae1881628]
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(PostgresSingleUserMain+0xc4)[0xaaaae1701a34]
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(main+0x6ac)[0xaaaae12a2adc]
/lib/aarch64-linux-gnu/libc.so.6(__libc_start_main+0xe8)[0xffff99713dd8]
/home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres(+0xf2b98)[0xaaaae12a2b98]
Aborted
pg_rewind: error: postgres single-user mode in target cluster failed
pg_rewind: detail: Command was: /home/admin/batta/buildroot/HEAD/pgsql.build/tmp_install/home/admin/batta/buildroot/HEAD/inst/bin/postgres --single -F -D /home/admin/batta/buildroot/HEAD/pgsql.build/src/bin/pg_rewind/tmp_check/t_001_basic_primary_local_data/pgdata -c config_file=/home/admin/batta/buildroot/HEAD/pgsql.build/src/bin/pg_rewind/tmp_check/tmp_test_QbsG/primary-postgresql.conf.tmp template1 < /dev/null

Presumably the reason that batta failed is its special configuration:

shared_preload_libraries = 'pg_stat_statements'; regress_dump_restore; wal_consistency_checking; compute_query_id = regress; --enable-injection-points

Greetings,

Andres Freund

Commits

  1. Fix outdated comment on MainLWLockArray

  2. Fix RequestNamedLWLockTranche in single-user mode

  3. Minor comment fixes to yesterday's LWLock tranche refactoring

  4. Move ShmemIndexLock into ShmemAllocator

  5. Use ShmemInitStruct to allocate lwlock.c's shared memory

  6. Use a separate spinlock to protect LWLockTranches

  7. Refactor how user-defined LWLock tranches are stored in shmem

  8. Rename MAX_NAMED_TRANCHES to MAX_USER_DEFINED_TRANCHES

  9. Fix re-initialization of LWLock-related shared memory.