Function ReinitializeParallelDSM

src/backend/access/transam/parallel.c:523–565

* Reinitialize the dynamic shared memory segment for a parallel context such * that we could launch workers for it again. */

 * that we could launch workers for it again.
 */
void
ReinitializeParallelDSM(ParallelContext *pcxt)
{
	FixedParallelState *fps;

	/* Wait for any old workers to exit. */
	if (pcxt->nworkers_launched > 0)
	{
		WaitForParallelWorkersToFinish(pcxt);
		WaitForParallelWorkersToExit(pcxt);
		pcxt->nworkers_launched = 0;
		if (pcxt->known_attached_workers)
		{
			pfree(pcxt->known_attached_workers);
			pcxt->known_attached_workers = NULL;
			pcxt->nknown_attached_workers = 0;
		}
	}

	/* Reset a few bits of fixed parallel state to a clean state. */
	fps = shm_toc_lookup(pcxt->toc, PARALLEL_KEY_FIXED, false);
	fps->last_xlog_end = 0;

	/* Recreate error queues (if they exist). */
	if (pcxt->nworkers > 0)
	{
		char	   *error_queue_space;
		int			i;

		error_queue_space =
			shm_toc_lookup(pcxt->toc, PARALLEL_KEY_ERROR_QUEUE, false);
		for (i = 0; i < pcxt->nworkers; ++i)
		{
			char	   *start;
			shm_mq	   *mq;

			start = error_queue_space + i * PARALLEL_ERROR_QUEUE_SIZE;
			mq = shm_mq_create(start, PARALLEL_ERROR_QUEUE_SIZE);
			shm_mq_set_receiver(mq, MyProc);
			pcxt->worker[i].error_mqh = shm_mq_attach(mq, pcxt->seg, NULL);
		}
	}
}

/*
 * Reinitialize parallel workers for a parallel context such that we could