From db6f070e73f89c38f8a2bfafa10b0718ea51a57d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=C3=81lvaro=20Herrera?= Date: Mon, 18 May 2026 10:13:24 -0700 Subject: [PATCH] Restructure repack worker teardown MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The original code would leave a shared memory segment unreleased if we fail partway through initialization. Change the shutdown order so that we already free it. Author: Álvaro Herrera Discussion: https://postgr.es/m/agtNn6ZCmdI2KJFn@alvherre.pgsql --- src/backend/commands/repack.c | 67 ++++++++++++++++------------------- 1 file changed, 31 insertions(+), 36 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index bfc62c8f752..c9064d8fd13 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -3411,10 +3411,14 @@ start_repack_decoding_worker(Oid relid) shm_mq_handle *mqh; BackgroundWorker bgw; + decoding_worker = palloc0_object(DecodingWorker); + /* Setup shared memory. */ size = BUFFERALIGN(offsetof(DecodingWorkerShared, error_queue)) + BUFFERALIGN(REPACK_ERROR_QUEUE_SIZE); seg = dsm_create(size, 0); + decoding_worker->seg = seg; + shared = (DecodingWorkerShared *) dsm_segment_address(seg); shared->initialized = false; shared->lsn_upto = InvalidXLogRecPtr; @@ -3454,14 +3458,12 @@ start_repack_decoding_worker(Oid relid) bgw.bgw_main_arg = UInt32GetDatum(dsm_segment_handle(seg)); bgw.bgw_notify_pid = MyProcPid; - decoding_worker = palloc0_object(DecodingWorker); if (!RegisterDynamicBackgroundWorker(&bgw, &decoding_worker->handle)) ereport(ERROR, errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED), errmsg("out of background worker slots"), errhint("You might need to increase \"%s\".", "max_worker_processes")); - decoding_worker->seg = seg; decoding_worker->error_mqh = mqh; /* @@ -3487,17 +3489,6 @@ start_repack_decoding_worker(Oid relid) ConditionVariableCancelSleep(); } -/* - * PG_ENSURE_ERROR_CLEANUP callback to stop the decoding worker. - * This ensures the worker is terminated on both ERROR and FATAL exits, - * unlike PG_FINALLY which only handles ERROR. - */ -static void -repack_decoding_worker_cleanup_cb(int code, Datum arg) -{ - stop_repack_decoding_worker(); -} - /* * Stop the decoding worker and cleanup the related resources. * @@ -3508,39 +3499,43 @@ static void stop_repack_decoding_worker(void) { BgwHandleStatus status; + dsm_segment *dsmseg; - /* Haven't reached the worker startup? */ + /* Nothing to do if no worker was set up. */ if (decoding_worker == NULL) return; - /* Could not register the worker? */ - if (decoding_worker->handle == NULL) - return; + /* Terminate the worker process, if one is running. */ + if (decoding_worker->handle != NULL) + { + TerminateBackgroundWorker(decoding_worker->handle); + /* The worker should really exit before the REPACK command does. */ + HOLD_INTERRUPTS(); + status = WaitForBackgroundWorkerShutdown(decoding_worker->handle); + RESUME_INTERRUPTS(); - TerminateBackgroundWorker(decoding_worker->handle); - /* The worker should really exit before the REPACK command does. */ - HOLD_INTERRUPTS(); - status = WaitForBackgroundWorkerShutdown(decoding_worker->handle); - RESUME_INTERRUPTS(); - - if (status == BGWH_POSTMASTER_DIED) - ereport(FATAL, - errcode(ERRCODE_ADMIN_SHUTDOWN), - errmsg("postmaster exited during REPACK command")); - - shm_mq_detach(decoding_worker->error_mqh); + if (status == BGWH_POSTMASTER_DIED) + ereport(FATAL, + errcode(ERRCODE_ADMIN_SHUTDOWN), + errmsg("postmaster exited during REPACK command")); + } /* - * If we could not cancel the current sleep due to ERROR, do that before - * we detach from the shared memory the condition variable is located in. - * If we did not, the bgworker ERROR handling code would try and fail - * badly. + * Now detach from our shared memory segment. In error cases there might + * still be messages from the worker in the queue, which ProcessInterrupts + * would try to read; this is pointless (and causes an assertion failure), + * so set the global pointer to NULL to have ProcessRepackMessages ignore + * them. */ - ConditionVariableCancelSleep(); - - dsm_detach(decoding_worker->seg); + dsmseg = decoding_worker->seg; pfree(decoding_worker); decoding_worker = NULL; + + /* We must also cancel the current sleep, if one is still set up */ + ConditionVariableCancelSleep(); + + if (dsmseg != NULL) + dsm_detach(dsmseg); } /* stop_repack_decoding_worker, wrapped as a before_shmem_exit callback */ -- 2.47.3