Function enterpgrp

freebsd/kern/kern_proc.c:570–626

* Create a new process group. * pgid must be equal to the pid of p. * Begin a new session if required. */

 * Begin a new session if required.
 */
int
enterpgrp(struct proc *p, pid_t pgid, struct pgrp *pgrp, struct session *sess)
{

	sx_assert(&proctree_lock, SX_XLOCKED);

	KASSERT(pgrp != NULL, ("enterpgrp: pgrp == NULL"));
	KASSERT(p->p_pid == pgid,
	    ("enterpgrp: new pgrp and pid != pgid"));
	KASSERT(pgfind(pgid) == NULL,
	    ("enterpgrp: pgrp with pgid exists"));
	KASSERT(!SESS_LEADER(p),
	    ("enterpgrp: session leader attempted setpgrp"));

	if (sess != NULL) {
		/*
		 * new session
		 */
		mtx_init(&sess->s_mtx, "session", NULL, MTX_DEF);
		PROC_LOCK(p);
		p->p_flag &= ~P_CONTROLT;
		PROC_UNLOCK(p);
		PGRP_LOCK(pgrp);
		sess->s_leader = p;
		sess->s_sid = p->p_pid;
		proc_id_set(PROC_ID_SESSION, p->p_pid);
		refcount_init(&sess->s_count, 1);
		sess->s_ttyvp = NULL;
		sess->s_ttydp = NULL;
		sess->s_ttyp = NULL;
		bcopy(p->p_session->s_login, sess->s_login,
			    sizeof(sess->s_login));
		pgrp->pg_session = sess;
		KASSERT(p == curproc,
		    ("enterpgrp: mksession and p != curproc"));
	} else {
		pgrp->pg_session = p->p_session;
		sess_hold(pgrp->pg_session);
		PGRP_LOCK(pgrp);
	}
	pgrp->pg_id = pgid;
	proc_id_set(PROC_ID_GROUP, p->p_pid);
	LIST_INIT(&pgrp->pg_members);
	pgrp->pg_flags = 0;

	/*
	 * As we have an exclusive lock of proctree_lock,
	 * this should not deadlock.
	 */
	LIST_INSERT_HEAD(PGRPHASH(pgid), pgrp, pg_hash);
	SLIST_INIT(&pgrp->pg_sigiolst);
	PGRP_UNLOCK(pgrp);

	doenterpgrp(p, pgrp);

	return (0);
}