Function InitProcess

src/backend/storage/lmgr/proc.c:348–626

* InitProcess -- initialize a per-process data structure for this backend */

 * InitProcess -- initialize a per-process data structure for this backend
 */
void
InitProcess(void)
{
	PGPROC	   *volatile *procgloballist;

	/*
	 * WAL sender, etc are marked as GP_ROLE_UTILITY to prevent unwanted
	 * GP_ROLE_DISPATCH MyProc settings such as mppSessionId being valid and
	 * mppIsWriter set to true.
	 */
	if (am_walsender || am_ftshandler || am_faulthandler)
		Gp_role = GP_ROLE_UTILITY;

	/*
	 * ProcGlobal should be set up already (if we are a backend, we inherit
	 * this by fork() or EXEC_BACKEND mechanism from the postmaster).
	 */
	if (ProcGlobal == NULL)
		elog(PANIC, "proc header uninitialized");

	if (MyProc != NULL)
		elog(ERROR, "you already exist");

	/* Decide which list should supply our PGPROC. */
	if (IsAnyAutoVacuumProcess())
		procgloballist = &ProcGlobal->autovacFreeProcs;
	else if (IsAnyLoginMonitorProcess())
		procgloballist = &ProcGlobal->lmFreeProcs;
	else if (IsBackgroundWorker)
		procgloballist = &ProcGlobal->bgworkerFreeProcs;
	else if (am_walsender)
		procgloballist = &ProcGlobal->walsenderFreeProcs;
	else
		procgloballist = &ProcGlobal->freeProcs;

	/*
	 * Try to get a proc struct from the appropriate free list.  If this
	 * fails, we must be out of PGPROC structures (not to mention semaphores).
	 *
	 * While we are holding the ProcStructLock, also copy the current shared
	 * estimate of spins_per_delay to local storage.
	 */
	SpinLockAcquire(ProcStructLock);

	set_spins_per_delay(ProcGlobal->spins_per_delay);

	MyProc = *procgloballist;

	if (MyProc != NULL)
	{
		*procgloballist = (PGPROC *) MyProc->links.next;
		SpinLockRelease(ProcStructLock);
	}
	else
	{
		/*
		 * If we reach here, all the PGPROCs are in use.  This is one of the
		 * possible places to detect "too many backends", so give the standard