clock_gettime(2): Fix CLOCK_PROCESS/THREAD_CPUTIME_ID.

Use same calculation as getrusage, not some ad-hoc arithmetic of
internal scheduler parameters that are periodically rewound.

PR kern/57512

XXX pullup-8
XXX pullup-9
XXX pullup-10

sys/kern/kern_resource.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_resource.c,v 1.190 2023/07/08 11:42:03 riastradh Exp $	*/
+/*	$NetBSD: kern_resource.c,v 1.191 2023/07/08 20:02:10 riastradh Exp $	*/
 
 /*-
  * Copyright (c) 1982, 1986, 1991, 1993
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_resource.c,v 1.190 2023/07/08 11:42:03 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_resource.c,v 1.191 2023/07/08 20:02:10 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -478,6 +478,30 @@ sys_getrlimit(struct lwp *l, const struct sys_getrlimit_args *uap,
 	return copyout(&rl, SCARG(uap, rlp), sizeof(rl));
 }
 
+void
+addrulwp(struct lwp *l, struct bintime *tm)
+{
+
+	lwp_lock(l);
+	bintime_add(tm, &l->l_rtime);
+	if ((l->l_pflag & LP_RUNNING) != 0 &&
+	    (l->l_pflag & (LP_INTR | LP_TIMEINTR)) != LP_INTR) {
+		struct bintime diff;
+		/*
+		 * Adjust for the current time slice.  This is
+		 * actually fairly important since the error
+		 * here is on the order of a time quantum,
+		 * which is much greater than the sampling
+		 * error.
+		 */
+		binuptime(&diff);
+		membar_consumer(); /* for softint_dispatch() */
+		bintime_sub(&diff, &l->l_stime);
+		bintime_add(tm, &diff);
+	}
+	lwp_unlock(l);
+}
+
 /*
  * Transform the running time and tick information in proc p into user,
  * system, and interrupt time usage.
@@ -504,24 +528,7 @@ calcru(struct proc *p, struct timeval *up, struct timeval *sp,
 	tm = p->p_rtime;
 
 	LIST_FOREACH(l, &p->p_lwps, l_sibling) {
-		lwp_lock(l);
+		addrulwp(l, &tm);
-		bintime_add(&tm, &l->l_rtime);
-		if ((l->l_pflag & LP_RUNNING) != 0 &&
-		    (l->l_pflag & (LP_INTR | LP_TIMEINTR)) != LP_INTR) {
-			struct bintime diff;
-			/*
-			 * Adjust for the current time slice.  This is
-			 * actually fairly important since the error
-			 * here is on the order of a time quantum,
-			 * which is much greater than the sampling
-			 * error.
-			 */
-			binuptime(&diff);
-			membar_consumer(); /* for softint_dispatch() */
-			bintime_sub(&diff, &l->l_stime);
-			bintime_add(&tm, &diff);
-		}
-		lwp_unlock(l);
 	}
 
 	tot = st + ut + it;

sys/kern/subr_time.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: subr_time.c,v 1.37 2023/04/29 03:36:55 isaki Exp $	*/
+/*	$NetBSD: subr_time.c,v 1.38 2023/07/08 20:02:10 riastradh Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.37 2023/04/29 03:36:55 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.38 2023/07/08 20:02:10 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -45,12 +45,6 @@ __KERNEL_RCSID(0, "$NetBSD: subr_time.c,v 1.37 2023/04/29 03:36:55 isaki Exp $")
 #include <sys/timetc.h>
 #include <sys/intr.h>
 
-#ifdef DEBUG_STICKS
-#define DPRINTF(a) uprintf a
-#else
-#define DPRINTF(a) 
-#endif
-
 /*
  * Compute number of hz until specified time.  Used to compute second
  * argument to callout_reset() from an absolute time.
@@ -248,32 +242,16 @@ clock_timeleft(clockid_t clockid, struct timespec *ts, struct timespec *sleepts)
 	*sleepts = sleptts;
 }
 
-static void
-ticks2ts(uint64_t ticks, struct timespec *ts)
-{
-	ts->tv_sec = ticks / hz;
-	uint64_t sticks = ticks - ts->tv_sec * hz;
-	if (sticks > BINTIME_SCALE_MS)	/* floor(2^64 / 1000) */
-		ts->tv_nsec = sticks / hz * 1000000000LL;
-	else if (sticks > BINTIME_SCALE_US)	/* floor(2^64 / 1000000) */
-		ts->tv_nsec = sticks * 1000LL / hz * 1000000LL;
-	else
-		ts->tv_nsec = sticks * 1000000000LL / hz;
-	DPRINTF(("%s: %ju/%ju -> %ju.%ju\n", __func__,
-	    (uintmax_t)ticks, (uintmax_t)sticks,
-	    (uintmax_t)ts->tv_sec, (uintmax_t)ts->tv_nsec));
-}
-
 int
 clock_gettime1(clockid_t clock_id, struct timespec *ts)
 {
 	int error;
-	uint64_t ticks;
 	struct proc *p;
 
 #define CPUCLOCK_ID_MASK (~(CLOCK_THREAD_CPUTIME_ID|CLOCK_PROCESS_CPUTIME_ID))
 	if (clock_id & CLOCK_PROCESS_CPUTIME_ID) {
 		pid_t pid = clock_id & CPUCLOCK_ID_MASK;
+		struct timeval cputime;
 
 		mutex_enter(&proc_lock);
 		p = pid == 0 ? curproc : proc_find(pid);
@@ -281,10 +259,10 @@ clock_gettime1(clockid_t clock_id, struct timespec *ts)
 			mutex_exit(&proc_lock);
 			return ESRCH;
 		}
-		ticks = p->p_uticks + p->p_sticks + p->p_iticks;
+		mutex_enter(p->p_lock);
-		DPRINTF(("%s: u=%ju, s=%ju, i=%ju\n", __func__,
+		calcru(p, /*usertime*/NULL, /*systime*/NULL, /*intrtime*/NULL,
-		    (uintmax_t)p->p_uticks, (uintmax_t)p->p_sticks,
+		    &cputime);
-		    (uintmax_t)p->p_iticks));
+		mutex_exit(p->p_lock);
 		mutex_exit(&proc_lock);
 
 		// XXX: Perhaps create a special kauth type
@@ -293,9 +271,14 @@ clock_gettime1(clockid_t clock_id, struct timespec *ts)
 		    KAUTH_ARG(KAUTH_REQ_PROCESS_CANSEE_ENTRY), NULL, NULL);
 		if (error)
 			return error;
+
+		TIMEVAL_TO_TIMESPEC(&cputime, ts);
+		return 0;
 	} else if (clock_id & CLOCK_THREAD_CPUTIME_ID) {
 		struct lwp *l;
 		lwpid_t lid = clock_id & CPUCLOCK_ID_MASK;
+		struct bintime tm = {0, 0};
+
 		p = curproc;
 		mutex_enter(p->p_lock);
 		l = lid == 0 ? curlwp : lwp_find(p, lid);
@@ -303,15 +286,10 @@ clock_gettime1(clockid_t clock_id, struct timespec *ts)
 			mutex_exit(p->p_lock);
 			return ESRCH;
 		}
-		ticks = l->l_rticksum + l->l_slpticksum;
+		addrulwp(l, &tm);
-		DPRINTF(("%s: r=%ju, s=%ju\n", __func__,
-		    (uintmax_t)l->l_rticksum, (uintmax_t)l->l_slpticksum));
 		mutex_exit(p->p_lock);
-	} else
-		ticks = (uint64_t)-1;
 
-	if (ticks != (uint64_t)-1) {
+		bintime2timespec(&tm, ts);
-		ticks2ts(ticks, ts);
 		return 0;
 	}
 

sys/sys/resourcevar.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: resourcevar.h,v 1.57 2018/05/07 21:03:45 christos Exp $	*/
+/*	$NetBSD: resourcevar.h,v 1.58 2023/07/08 20:02:10 riastradh Exp $	*/
 
 /*
  * Copyright (c) 1991, 1993
@@ -41,6 +41,8 @@
 #include <sys/mutex.h>
 #include <sys/resource.h>
 
+struct bintime;
+
 /*
  * Kernel per-process accounting / statistics
  */
@@ -107,6 +109,7 @@ void	addupc_intr(struct lwp *, u_long);
 void	addupc_task(struct lwp *, u_long, u_int);
 void	calcru(struct proc *, struct timeval *, struct timeval *,
 	    struct timeval *, struct timeval *);
+void	addrulwp(struct lwp *, struct bintime *);
 
 struct plimit *lim_copy(struct plimit *);
 void	lim_addref(struct plimit *);

tests/lib/libc/sys/t_clock_gettime.c

@@ -1,4 +1,4 @@
-/* $NetBSD: t_clock_gettime.c,v 1.4 2023/07/08 14:05:51 riastradh Exp $ */
+/* $NetBSD: t_clock_gettime.c,v 1.5 2023/07/08 20:02:10 riastradh Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
 #include <sys/cdefs.h>
 __COPYRIGHT("@(#) Copyright (c) 2008\
  The NetBSD Foundation, inc. All rights reserved.");
-__RCSID("$NetBSD: t_clock_gettime.c,v 1.4 2023/07/08 14:05:51 riastradh Exp $");
+__RCSID("$NetBSD: t_clock_gettime.c,v 1.5 2023/07/08 20:02:10 riastradh Exp $");
 
 #include <sys/param.h>
 
@@ -281,8 +281,6 @@ ATF_TC_HEAD(clock_gettime_thread_cputime_is_monotonic, tc)
 }
 ATF_TC_BODY(clock_gettime_thread_cputime_is_monotonic, tc)
 {
-	atf_tc_expect_fail("PR kern/57512: clock_gettime"
-	    "(CLOCK_THREAD_CPUTIME_ID) sometimes goes backwards");
 	check_monotonicity("CLOCK_THREAD_CPUTIME_ID",
 	    CLOCK_THREAD_CPUTIME_ID, &waste_user_time);
 }