Function SubPostmasterMain

src/backend/postmaster/postmaster.c:5470–5696

* SubPostmasterMain -- Get the fork/exec'd process into a state equivalent * to what it would be if we'd simply forked on Unix, and then * dispatch to the appropriate place. * * The first two command line arguments are expected to be "--forkFOO" * (where FOO indicates which postmaster child we are to become), and * the name of a variables file that we can read to load data that would *

 * subprocess FooMain() routine.
 */
void
SubPostmasterMain(int argc, char *argv[])
{
	Port		port;

	/* In EXEC_BACKEND case we will not have inherited these settings */
	IsPostmasterEnvironment = true;
	whereToSendOutput = DestNone;

	/* Setup essential subsystems (to ensure elog() behaves sanely) */
	InitializeGUCOptions();

	/* Check we got appropriate args */
	if (argc < 3)
		elog(FATAL, "invalid subpostmaster invocation");

	/* Read in the variables file */
	memset(&port, 0, sizeof(Port));
	read_backend_variables(argv[2], &port);

	/* Close the postmaster's sockets (as soon as we know them) */
	ClosePostmasterPorts(strcmp(argv[1], "--forklog") == 0);

	/*
	 * Start our win32 signal implementation. This has to be done after we
	 * read the backend variables, because we need to pick up the signal pipe
	 * from the parent process.
	 */
#ifdef WIN32
	pgwin32_signal_initialize();
#endif

	/* Setup as postmaster child */
	InitPostmasterChild();

	/*
	 * If appropriate, physically re-attach to shared memory segment. We want
	 * to do this before going any further to ensure that we can attach at the
	 * same address the postmaster used.  On the other hand, if we choose not
	 * to re-attach, we may have other cleanup to do.
	 *
	 * If testing EXEC_BACKEND on Linux, you should run this as root before
	 * starting the postmaster:
	 *
	 * echo 0 >/proc/sys/kernel/randomize_va_space
	 *
	 * This prevents using randomized stack and code addresses that cause the
	 * child process's memory map to be different from the parent's, making it
	 * sometimes impossible to attach to shared memory at the desired address.
	 * Return the setting to its old value (usually '1' or '2') when finished.
	 */
	if (strcmp(argv[1], "--forkbackend") == 0   ||
		strcmp(argv[1], "--forkavlauncher") == 0 ||
		strcmp(argv[1], "--forkavworker") == 0 ||
		strcmp(argv[1], "--forkautovac") == 0   ||
		strcmp(argv[1], "--forkglobaldeadlockdetector") == 0 ||
		strcmp(argv[1], "--forkboot") == 0 ||
		strncmp(argv[1], "--forkbgworker=", 15) == 0)