From 245f17d43c96de12ada70fbd8bcad637db53136d Mon Sep 17 00:00:00 2001
From: Joerg Wunsch <joerg@FreeBSD.org>
Date: Sat, 13 Sep 1997 19:42:29 +0000
Subject: [PATCH] Implement SA_NOCLDWAIT.

The implementation is done (unlike what i've originally been
contemplating) by reparenting kids of processes that have the
appropriate bit set to PID 1, and let PID 1 handle the zombie.  This
is far less problematical than what would seem to be ``doing it
right'', for a number of reasons.

Of our currently shipping PID-1-intended programs, 50 % fail the above
assumption. ;-)  (Read this: sysinstall doesn't do it right.  This is
no problem as long as no program called by sysinstall actually uses
SA_NOCLDWAIT.)

ToDo:		. clarify the correct SA_* flag inheritance, compared
		  to other systems,
		. decide whether the compat cruft (osigvec(9)) should
		  deal with new system additions or not,
		. merge OpenBSD's SA_SIGINFO implementation. ;)
Reviewed by:	bde
---
 sys/kern/kern_exit.c | 18 ++++++++++++++++--
 sys/kern/kern_sig.c  | 17 ++++++++++++++++-
 sys/sys/_sigset.h    |  3 ++-
 sys/sys/proc.h       |  5 ++++-
 sys/sys/signal.h     |  3 ++-
 5 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index 7d326da9fd9b..1fb9077797de 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_exit.c	8.7 (Berkeley) 2/12/94
- * $Id: kern_exit.c,v 1.53 1997/08/26 00:11:55 bde Exp $
+ * $Id: kern_exit.c,v 1.54 1997/09/02 20:05:38 bde Exp $
  */
 
 #include "opt_ktrace.h"
@@ -294,8 +294,22 @@ exit1(p, rv)
 	ruadd(p->p_ru, &p->p_stats->p_cru);
 
 	/*
-	 * Notify parent that we're gone.
+	 * Notify parent that we're gone.  If parent has the P_NOCLDWAIT
+	 * flag set, notify process 1 instead (and hope it will handle
+	 * this situation).
 	 */
+	if (p->p_pptr->p_flag & P_NOCLDWAIT) {
+		struct proc *pp = p->p_pptr;
+		proc_reparent(p, initproc);
+		/*
+		 * If this was the last child of our parent, notify
+		 * parent, so in case he was wait(2)ing, he will
+		 * continue.
+		 */
+		if (LIST_EMPTY(&pp->p_children))
+			wakeup((caddr_t)pp);
+	}
+
 	psignal(p->p_pptr, SIGCHLD);
 	wakeup((caddr_t)p->p_pptr);
 #if defined(tahoe)
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index b73503e3111d..fb78d3e1ff67 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_sig.c	8.7 (Berkeley) 4/18/94
- * $Id: kern_sig.c,v 1.32 1997/08/26 00:31:04 bde Exp $
+ * $Id: kern_sig.c,v 1.33 1997/09/02 20:05:41 bde Exp $
  */
 
 #include "opt_ktrace.h"
@@ -123,6 +123,8 @@ sigaction(p, uap, retval)
 			sa->sa_flags |= SA_NODEFER;
 		if (signum == SIGCHLD && p->p_flag & P_NOCLDSTOP)
 			sa->sa_flags |= SA_NOCLDSTOP;
+		if (signum == SIGCHLD && p->p_flag & P_NOCLDWAIT)
+			sa->sa_flags |= SA_NOCLDWAIT;
 		if ((error = copyout((caddr_t)sa, (caddr_t)uap->osa,
 		    sizeof (vec))))
 			return (error);
@@ -182,6 +184,19 @@ setsigvec(p, signum, sa)
 			p->p_flag |= P_NOCLDSTOP;
 		else
 			p->p_flag &= ~P_NOCLDSTOP;
+		if (sa->sa_flags & SA_NOCLDWAIT) {
+			/*
+			 * Paranoia: since SA_NOCLDWAIT is implemented by
+			 * reparenting the dying child to PID 1 (and
+			 * trust it to reap the zombie), PID 1 itself is
+			 * forbidden to set SA_NOCLDWAIT.
+			 */
+			if (p->p_pid == 1)
+				p->p_flag &= ~P_NOCLDWAIT;
+			else
+				p->p_flag |= P_NOCLDWAIT;
+		} else
+			p->p_flag &= ~P_NOCLDWAIT;
 	}
 	/*
 	 * Set bit in p_sigignore for signals that are set to SIG_IGN,
diff --git a/sys/sys/_sigset.h b/sys/sys/_sigset.h
index f461a99d55c2..ee3cabb4cae4 100644
--- a/sys/sys/_sigset.h
+++ b/sys/sys/_sigset.h
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)signal.h	8.4 (Berkeley) 5/4/95
- * $Id$
+ * $Id: signal.h,v 1.11 1997/02/22 09:45:53 peter Exp $
  */
 
 #ifndef	_SYS_SIGNAL_H_
@@ -132,6 +132,7 @@ struct	sigaction {
 #define SA_RESTART	0x0002	/* restart system call on signal return */
 #define	SA_RESETHAND	0x0004	/* reset to SIG_DFL when taking signal */
 #define	SA_NODEFER	0x0010	/* don't mask the signal we're delivering */
+#define	SA_NOCLDWAIT	0x0020	/* don't keep zombies around */
 #ifdef COMPAT_SUNOS
 #define	SA_USERTRAMP	0x0100	/* do not bounce off kernel's sigtramp */
 #endif
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index cb64b36daa72..842a541726af 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)proc.h	8.15 (Berkeley) 5/19/95
- * $Id: proc.h,v 1.41 1997/06/22 16:04:22 peter Exp $
+ * $Id: proc.h,v 1.42 1997/07/06 02:40:36 dyson Exp $
  */
 
 #ifndef _SYS_PROC_H_
@@ -224,6 +224,9 @@ struct	proc {
 /* Marked a kernel thread */
 #define P_KTHREADP	0x200000 /* Process is really a kernel thread */
 
+#define	P_NOCLDWAIT	0x400000 /* No zombies if child dies */
+
+
 /*
  * MOVE TO ucred.h?
  *
diff --git a/sys/sys/signal.h b/sys/sys/signal.h
index f461a99d55c2..ee3cabb4cae4 100644
--- a/sys/sys/signal.h
+++ b/sys/sys/signal.h
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)signal.h	8.4 (Berkeley) 5/4/95
- * $Id$
+ * $Id: signal.h,v 1.11 1997/02/22 09:45:53 peter Exp $
  */
 
 #ifndef	_SYS_SIGNAL_H_
@@ -132,6 +132,7 @@ struct	sigaction {
 #define SA_RESTART	0x0002	/* restart system call on signal return */
 #define	SA_RESETHAND	0x0004	/* reset to SIG_DFL when taking signal */
 #define	SA_NODEFER	0x0010	/* don't mask the signal we're delivering */
+#define	SA_NOCLDWAIT	0x0020	/* don't keep zombies around */
 #ifdef COMPAT_SUNOS
 #define	SA_USERTRAMP	0x0100	/* do not bounce off kernel's sigtramp */
 #endif