Function UpdateSharedMemoryConfig

src/backend/postmaster/checkpointer.c:1328–1341

* Update any shared memory configurations based on config parameters */

 * Update any shared memory configurations based on config parameters
 */
static void
UpdateSharedMemoryConfig(void)
{
	/* update global shmem state for sync rep */
	SyncRepUpdateSyncStandbysDefined();

	/*
	 * If full_page_writes has been changed by SIGHUP, we update it in shared
	 * memory and write an XLOG_FPW_CHANGE record.
	 */
	UpdateFullPageWrites();

	elog(DEBUG2, "checkpointer updated shared memory configuration values");
}

/*
 * FirstCallSinceLastCheckpoint allows a process to take an action once