[src/trunk]: src/sys/kern avoid underflow in user/system time.

[mlelstv <mlelstv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/04a710d58a0a
branches:  trunk
changeset: 455511:04a710d58a0a
user:      mlelstv <mlelstv%NetBSD.org@localhost>
date:      Fri Apr 05 00:33:21 2019 +0000

description:
avoid underflow in user/system time.

diffstat:

 sys/kern/kern_resource.c |  12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diffs (42 lines):

diff -r 090969721698 -r 04a710d58a0a sys/kern/kern_resource.c
--- a/sys/kern/kern_resource.c  Thu Apr 04 22:49:46 2019 +0000
+++ b/sys/kern/kern_resource.c  Fri Apr 05 00:33:21 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_resource.c,v 1.181 2018/05/13 14:45:23 christos Exp $     */
+/*     $NetBSD: kern_resource.c,v 1.182 2019/04/05 00:33:21 mlelstv Exp $      */
 
 /*-
  * Copyright (c) 1982, 1986, 1991, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_resource.c,v 1.181 2018/05/13 14:45:23 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_resource.c,v 1.182 2019/04/05 00:33:21 mlelstv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -488,7 +488,7 @@
 calcru(struct proc *p, struct timeval *up, struct timeval *sp,
     struct timeval *ip, struct timeval *rp)
 {
-       uint64_t u, st, ut, it, tot;
+       uint64_t u, st, ut, it, tot, dt;
        struct lwp *l;
        struct bintime tm;
        struct timeval tv;
@@ -549,10 +549,12 @@
         * which must have increased.
         */
        if (p->p_xutime > ut) {
-               st -= p->p_xutime - ut;
+               dt = p->p_xutime - ut;
+               st -= uimin(dt, st);
                ut = p->p_xutime;
        } else if (p->p_xstime > st) {
-               ut -= p->p_xstime - st;
+               dt = p->p_xstime - st;
+               ut -= uimin(dt, ut);
                st = p->p_xstime;
        }