stop_all_proc(): skip traced or signal-stoped processes

Since thread_single(SINGLE_ALLPROC) ignores them since 9241ebc,
and there is not much we can do for the debugger-controlled process.

Noted by:	olce
Reviewed by:	markj, olce
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D44638

Author: kostikbel

sys/kern/kern_proc.c

@@ -3477,7 +3477,8 @@ stop_all_proc(void)
 		LIST_REMOVE(cp, p_list);
 		LIST_INSERT_AFTER(p, cp, p_list);
 		PROC_LOCK(p);
-		if ((p->p_flag & (P_KPROC | P_SYSTEM | P_TOTAL_STOP)) != 0) {
+		if ((p->p_flag & (P_KPROC | P_SYSTEM | P_TOTAL_STOP |
+		    P_STOPPED_SIG)) != 0) {
 			PROC_UNLOCK(p);
 			continue;
 		}
@@ -3498,6 +3499,16 @@ stop_all_proc(void)
 			PROC_UNLOCK(p);
 			continue;
 		}
+		if ((p->p_flag & P_TRACED) != 0) {
+			/*
+			 * thread_single() below cannot stop traced p,
+			 * so skip it.  OTOH, we cannot require
+			 * restart because debugger might be either
+			 * already stopped or traced as well.
+			 */
+			PROC_UNLOCK(p);
+			continue;
+		}
 		sx_xunlock(&allproc_lock);
 		_PHOLD(p);
 		r = thread_single(p, SINGLE_ALLPROC);