Simplify pid selection algorithm. ok art@ deraadt@

1 files changed, 23 insertions, 45 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 6c8c72c04e5..5c5e49446e3 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_fork.c,v 1.51 2002/02/14 22:58:15 art Exp $	*/
+/*	$OpenBSD: kern_fork.c,v 1.52 2002/02/16 00:54:49 nordin Exp $	*/
 /*	$NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $	*/
 
 /*
@@ -69,6 +69,7 @@ int	randompid;		/* when set to 1, pid's go random */
 pid_t	lastpid;
 struct	forkstat forkstat;
 
+int pidtaken(pid_t);
 
 /*ARGSUSED*/
 int
@@ -148,7 +149,6 @@ fork1(p1, exitsig, flags, stack, stacksize, func, arg, retval)
 	struct proc *newproc;
 	struct vmspace *vm;
 	int count;
-	static int pidchecked = 0;
 	vaddr_t uaddr;
 	int s;
 	extern void endtsleep __P((void *));
@@ -186,49 +186,10 @@ fork1(p1, exitsig, flags, stack, stacksize, func, arg, retval)
 	/* Allocate new proc. */
 	newproc = pool_get(&proc_pool, PR_WAITOK);
 
-	lastpid++;
-	if (randompid)
-		lastpid = PID_MAX;
-retry:
-	/*
-	 * If the process ID prototype has wrapped around,
-	 * restart somewhat above 0, as the low-numbered procs
-	 * tend to include daemons that don't exit.
-	 */
-	if (lastpid >= PID_MAX) {
-		lastpid = arc4random() % PID_MAX;
-		pidchecked = 0;
-	}
-	if (lastpid >= pidchecked) {
-		int doingzomb = 0;
-
-		pidchecked = PID_MAX;
-		/*
-		 * Scan the active and zombie procs to check whether this pid
-		 * is in use.  Remember the lowest pid that's greater
-		 * than lastpid, so we can avoid checking for a while.
-		 */
-		p2 = LIST_FIRST(&allproc);
-again:
-		for (; p2 != 0; p2 = LIST_NEXT(p2, p_list)) {
-			while (p2->p_pid == lastpid ||
-			    p2->p_pgrp->pg_id == lastpid) {
-				lastpid++;
-				if (lastpid >= pidchecked)
-					goto retry;
-			}
-			if (p2->p_pid > lastpid && pidchecked > p2->p_pid)
-				pidchecked = p2->p_pid;
-			if (p2->p_pgrp->pg_id > lastpid && 
-			    pidchecked > p2->p_pgrp->pg_id)
-				pidchecked = p2->p_pgrp->pg_id;
-		}
-		if (!doingzomb) {
-			doingzomb = 1;
-			p2 = LIST_FIRST(&zombproc);
-			goto again;
-		}
-	}
+	/* Find an unused pid satisfying 1 <= lastpid <= PID_MAX */
+	do {
+		lastpid = 1 + (randompid ? arc4random() : lastpid) % PID_MAX;
+	} while (pidtaken(lastpid));
 
 	nprocs++;
 	p2 = newproc;
@@ -415,3 +376,20 @@ again:
 	return (0);
 }
 
+/*
+ * Checks for current use of a pid, either as a pid or pgid.
+ */
+int
+pidtaken(pid_t pid)
+{
+	struct proc *p;
+
+	if (pfind(pid) != NULL)
+		return (1);
+	if (pgfind(pid) != NULL)
+		return (1);
+	LIST_FOREACH(p, &zombproc, p_list)
+		if (p->p_pid == pid || p->p_pgid == pid)
+			return (1);
+	return (0);
+}