Lock struct pgrp, session and sigio.

New locks are:

- pgrpsess_lock which locks the whole pgrps and sessions,
- pg_mtx which protects the pgrp members, and
- s_mtx which protects the session members.

Please refer to sys/proc.h for the coverage of these locks.

Changes on the pgrp/session interface:

- pgfind() needs the pgrpsess_lock held.

- The caller of enterpgrp() is responsible to allocate a new pgrp and
  session.

- Call enterthispgrp() in order to enter an existing pgrp.

- pgsignal() requires a pgrp lock held.

Reviewed by:	jhb, alfred
Tested on:	cvsup.jp.FreeBSD.org
		(which is a quad-CPU machine running -current)

1 files changed, 7 insertions, 1 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 8fe1006..69071a1 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -382,12 +382,15 @@ retry:
 		p2 = LIST_FIRST(&allproc);
 again:
 		for (; p2 != NULL; p2 = LIST_NEXT(p2, p_list)) {
+			PROC_LOCK(p2);
 			while (p2->p_pid == trypid ||
 			    p2->p_pgrp->pg_id == trypid ||
 			    p2->p_session->s_sid == trypid) {
 				trypid++;
-				if (trypid >= pidchecked)
+				if (trypid >= pidchecked) {
+					PROC_UNLOCK(p2);
 					goto retry;
+				}
 			}
 			if (p2->p_pid > trypid && pidchecked > p2->p_pid)
 				pidchecked = p2->p_pid;
@@ -397,6 +400,7 @@ again:
 			if (p2->p_session->s_sid > trypid &&
 			    pidchecked > p2->p_session->s_sid)
 				pidchecked = p2->p_session->s_sid;
+			PROC_UNLOCK(p2);
 		}
 		if (!doingzomb) {
 			doingzomb = 1;
@@ -559,8 +563,10 @@ again:
 	 * been preserved.
 	 */
 	p2->p_flag |= p1->p_flag & (P_SUGID | P_ALTSTACK);
+	SESS_LOCK(p1->p_session);
 	if (p1->p_session->s_ttyvp != NULL && p1->p_flag & P_CONTROLT)
 		p2->p_flag |= P_CONTROLT;
+	SESS_UNLOCK(p1->p_session);
 	if (flags & RFPPWAIT)
 		p2->p_flag |= P_PPWAIT;