[S390] cputime: add sparse checking and cleanup

Make cputime_t and cputime64_t nocast to enable sparse checking to
detect incorrect use of cputime. Drop the cputime macros for simple
scalar operations. The conversion macros are still needed.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

11 files changed, 116 insertions, 174 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index fa7eb3de2ddc..203dfead2e06 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -613,8 +613,8 @@ void acct_collect(long exitcode, int group_dead)
 		pacct->ac_flag |= ACORE;
 	if (current->flags & PF_SIGNALED)
 		pacct->ac_flag |= AXSIG;
-	pacct->ac_utime = cputime_add(pacct->ac_utime, current->utime);
-	pacct->ac_stime = cputime_add(pacct->ac_stime, current->stime);
+	pacct->ac_utime += current->utime;
+	pacct->ac_stime += current->stime;
 	pacct->ac_minflt += current->min_flt;
 	pacct->ac_majflt += current->maj_flt;
 	spin_unlock_irq(&current->sighand->siglock);
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 563f13609470..3f8ee8a138c4 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -178,8 +178,7 @@ static inline void check_for_tasks(int cpu)
 	write_lock_irq(&tasklist_lock);
 	for_each_process(p) {
 		if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
-		    (!cputime_eq(p->utime, cputime_zero) ||
-		     !cputime_eq(p->stime, cputime_zero)))
+		    (p->utime || p->stime))
 			printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
 				"(state = %ld, flags = %x)\n",
 				p->comm, task_pid_nr(p), cpu,
diff --git a/kernel/exit.c b/kernel/exit.c
index d0b7d988f873..5e0d1f4c696e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -121,9 +121,9 @@ static void __exit_signal(struct task_struct *tsk)
 		 * We won't ever get here for the group leader, since it
 		 * will have been the last reference on the signal_struct.
 		 */
-		sig->utime = cputime_add(sig->utime, tsk->utime);
-		sig->stime = cputime_add(sig->stime, tsk->stime);
-		sig->gtime = cputime_add(sig->gtime, tsk->gtime);
+		sig->utime += tsk->utime;
+		sig->stime += tsk->stime;
+		sig->gtime += tsk->gtime;
 		sig->min_flt += tsk->min_flt;
 		sig->maj_flt += tsk->maj_flt;
 		sig->nvcsw += tsk->nvcsw;
@@ -1255,19 +1255,9 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 		spin_lock_irq(&p->real_parent->sighand->siglock);
 		psig = p->real_parent->signal;
 		sig = p->signal;
-		psig->cutime =
-			cputime_add(psig->cutime,
-			cputime_add(tgutime,
-				    sig->cutime));
-		psig->cstime =
-			cputime_add(psig->cstime,
-			cputime_add(tgstime,
-				    sig->cstime));
-		psig->cgtime =
-			cputime_add(psig->cgtime,
-			cputime_add(p->gtime,
-			cputime_add(sig->gtime,
-				    sig->cgtime)));
+		psig->cutime += tgutime + sig->cutime;
+		psig->cstime += tgstime + sig->cstime;
+		psig->cgtime += p->gtime + sig->gtime + sig->cgtime;
 		psig->cmin_flt +=
 			p->min_flt + sig->min_flt + sig->cmin_flt;
 		psig->cmaj_flt +=
diff --git a/kernel/fork.c b/kernel/fork.c
index da4a6a10d088..b058c5820ecd 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1023,8 +1023,8 @@ void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
  */
 static void posix_cpu_timers_init(struct task_struct *tsk)
 {
-	tsk->cputime_expires.prof_exp = cputime_zero;
-	tsk->cputime_expires.virt_exp = cputime_zero;
+	tsk->cputime_expires.prof_exp = 0;
+	tsk->cputime_expires.virt_exp = 0;
 	tsk->cputime_expires.sched_exp = 0;
 	INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 	INIT_LIST_HEAD(&tsk->cpu_timers[1]);
@@ -1132,14 +1132,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 
 	init_sigpending(&p->pending);
 
-	p->utime = cputime_zero;
-	p->stime = cputime_zero;
-	p->gtime = cputime_zero;
-	p->utimescaled = cputime_zero;
-	p->stimescaled = cputime_zero;
+	p->utime = p->stime = p->gtime = 0;
+	p->utimescaled = p->stimescaled = 0;
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
-	p->prev_utime = cputime_zero;
-	p->prev_stime = cputime_zero;
+	p->prev_utime = p->prev_stime = 0;
 #endif
 #if defined(SPLIT_RSS_COUNTING)
 	memset(&p->rss_stat, 0, sizeof(p->rss_stat));
diff --git a/kernel/itimer.c b/kernel/itimer.c
index d802883153da..22000c3db0dd 100644
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -52,22 +52,22 @@ static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 
 	cval = it->expires;
 	cinterval = it->incr;
-	if (!cputime_eq(cval, cputime_zero)) {
+	if (cval) {
 		struct task_cputime cputime;
 		cputime_t t;
 
 		thread_group_cputimer(tsk, &cputime);
 		if (clock_id == CPUCLOCK_PROF)
-			t = cputime_add(cputime.utime, cputime.stime);
+			t = cputime.utime + cputime.stime;
 		else
 			/* CPUCLOCK_VIRT */
 			t = cputime.utime;
 
-		if (cputime_le(cval, t))
+		if (cval < t)
 			/* about to fire */
 			cval = cputime_one_jiffy;
 		else
-			cval = cputime_sub(cval, t);
+			cval = cval - t;
 	}
 
 	spin_unlock_irq(&tsk->sighand->siglock);
@@ -161,10 +161,9 @@ static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
 
 	cval = it->expires;
 	cinterval = it->incr;
-	if (!cputime_eq(cval, cputime_zero) ||
-	    !cputime_eq(nval, cputime_zero)) {
-		if (cputime_gt(nval, cputime_zero))
-			nval = cputime_add(nval, cputime_one_jiffy);
+	if (cval || nval) {
+		if (nval > 0)
+			nval += cputime_one_jiffy;
 		set_process_cpu_timer(tsk, clock_id, &nval, &cval);
 	}
 	it->expires = nval;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index e7cb76dc18f5..125cb67daa21 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -78,7 +78,7 @@ static inline int cpu_time_before(const clockid_t which_clock,
 	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 		return now.sched < then.sched;
 	}  else {
-		return cputime_lt(now.cpu, then.cpu);
+		return now.cpu < then.cpu;
 	}
 }
 static inline void cpu_time_add(const clockid_t which_clock,
@@ -88,7 +88,7 @@ static inline void cpu_time_add(const clockid_t which_clock,
 	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 		acc->sched += val.sched;
 	}  else {
-		acc->cpu = cputime_add(acc->cpu, val.cpu);
+		acc->cpu += val.cpu;
 	}
 }
 static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
@@ -98,25 +98,12 @@ static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
 	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 		a.sched -= b.sched;
 	}  else {
-		a.cpu = cputime_sub(a.cpu, b.cpu);
+		a.cpu -= b.cpu;
 	}
 	return a;
 }
 
 /*
- * Divide and limit the result to res >= 1
- *
- * This is necessary to prevent signal delivery starvation, when the result of
- * the division would be rounded down to 0.
- */
-static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
-{
-	cputime_t res = cputime_div(time, div);
-
-	return max_t(cputime_t, res, 1);
-}
-
-/*
  * Update expiry time from increment, and increase overrun count,
  * given the current clock sample.
  */
@@ -148,28 +135,26 @@ static void bump_cpu_timer(struct k_itimer *timer,
 	} else {
 		cputime_t delta, incr;
 
-		if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
+		if (now.cpu < timer->it.cpu.expires.cpu)
 			return;
 		incr = timer->it.cpu.incr.cpu;
-		delta = cputime_sub(cputime_add(now.cpu, incr),
-				    timer->it.cpu.expires.cpu);
+		delta = now.cpu + incr - timer->it.cpu.expires.cpu;
 		/* Don't use (incr*2 < delta), incr*2 might overflow. */
-		for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
-			     incr = cputime_add(incr, incr);
-		for (; i >= 0; incr = cputime_halve(incr), i--) {
-			if (cputime_lt(delta, incr))
+		for (i = 0; incr < delta - incr; i++)
+			     incr += incr;
+		for (; i >= 0; incr = incr >> 1, i--) {
+			if (delta < incr)
 				continue;
-			timer->it.cpu.expires.cpu =
-				cputime_add(timer->it.cpu.expires.cpu, incr);
+			timer->it.cpu.expires.cpu += incr;
 			timer->it_overrun += 1 << i;
-			delta = cputime_sub(delta, incr);
+			delta -= incr;
 		}
 	}
 }
 
 static inline cputime_t prof_ticks(struct task_struct *p)
 {
-	return cputime_add(p->utime, p->stime);
+	return p->utime + p->stime;
 }
 static inline cputime_t virt_ticks(struct task_struct *p)
 {
@@ -248,8 +233,8 @@ void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 
 	t = tsk;
 	do {
-		times->utime = cputime_add(times->utime, t->utime);
-		times->stime = cputime_add(times->stime, t->stime);
+		times->utime += t->utime;
+		times->stime += t->stime;
 		times->sum_exec_runtime += task_sched_runtime(t);
 	} while_each_thread(tsk, t);
 out:
@@ -258,10 +243,10 @@ out:
 
 static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
 {
-	if (cputime_gt(b->utime, a->utime))
+	if (b->utime > a->utime)
 		a->utime = b->utime;
 
-	if (cputime_gt(b->stime, a->stime))
+	if (b->stime > a->stime)
 		a->stime = b->stime;
 
 	if (b->sum_exec_runtime > a->sum_exec_runtime)
@@ -306,7 +291,7 @@ static int cpu_clock_sample_group(const clockid_t which_clock,
 		return -EINVAL;
 	case CPUCLOCK_PROF:
 		thread_group_cputime(p, &cputime);
-		cpu->cpu = cputime_add(cputime.utime, cputime.stime);
+		cpu->cpu = cputime.utime + cputime.stime;
 		break;
 	case CPUCLOCK_VIRT:
 		thread_group_cputime(p, &cputime);
@@ -470,26 +455,24 @@ static void cleanup_timers(struct list_head *head,
 			   unsigned long long sum_exec_runtime)
 {
 	struct cpu_timer_list *timer, *next;
-	cputime_t ptime = cputime_add(utime, stime);
+	cputime_t ptime = utime + stime;
 
 	list_for_each_entry_safe(timer, next, head, entry) {
 		list_del_init(&timer->entry);
-		if (cputime_lt(timer->expires.cpu, ptime)) {
-			timer->expires.cpu = cputime_zero;
+		if (timer->expires.cpu < ptime) {
+			timer->expires.cpu = 0;
 		} else {
-			timer->expires.cpu = cputime_sub(timer->expires.cpu,
-							 ptime);
+			timer->expires.cpu -= ptime;
 		}
 	}
 
 	++head;
 	list_for_each_entry_safe(timer, next, head, entry) {
 		list_del_init(&timer->entry);
-		if (cputime_lt(timer->expires.cpu, utime)) {
-			timer->expires.cpu = cputime_zero;
+		if (timer->expires.cpu < utime) {
+			timer->expires.cpu = 0;
 		} else {
-			timer->expires.cpu = cputime_sub(timer->expires.cpu,
-							 utime);
+			timer->expires.cpu -= utime;
 		}
 	}
 
@@ -520,8 +503,7 @@ void posix_cpu_timers_exit_group(struct task_struct *tsk)
 	struct signal_struct *const sig = tsk->signal;
 
 	cleanup_timers(tsk->signal->cpu_timers,
-		       cputime_add(tsk->utime, sig->utime),
-		       cputime_add(tsk->stime, sig->stime),
+		       tsk->utime + sig->utime, tsk->stime + sig->stime,
 		       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 }
 
@@ -540,8 +522,7 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 
 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
 {
-	return cputime_eq(expires, cputime_zero) ||
-	       cputime_gt(expires, new_exp);
+	return expires == 0 || expires > new_exp;
 }
 
 /*
@@ -651,7 +632,7 @@ static int cpu_timer_sample_group(const clockid_t which_clock,
 	default:
 		return -EINVAL;
 	case CPUCLOCK_PROF:
-		cpu->cpu = cputime_add(cputime.utime, cputime.stime);
+		cpu->cpu = cputime.utime + cputime.stime;
 		break;
 	case CPUCLOCK_VIRT:
 		cpu->cpu = cputime.utime;
@@ -918,12 +899,12 @@ static void check_thread_timers(struct task_struct *tsk,
 	unsigned long soft;
 
 	maxfire = 20;
-	tsk->cputime_expires.prof_exp = cputime_zero;
+	tsk->cputime_expires.prof_exp = 0;
 	while (!list_empty(timers)) {
 		struct cpu_timer_list *t = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
+		if (!--maxfire || prof_ticks(tsk) < t->expires.cpu) {
 			tsk->cputime_expires.prof_exp = t->expires.cpu;
 			break;
 		}
@@ -933,12 +914,12 @@ static void check_thread_timers(struct task_struct *tsk,
 
 	++timers;
 	maxfire = 20;
-	tsk->cputime_expires.virt_exp = cputime_zero;
+	tsk->cputime_expires.virt_exp = 0;
 	while (!list_empty(timers)) {
 		struct cpu_timer_list *t = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
+		if (!--maxfire || virt_ticks(tsk) < t->expires.cpu) {
 			tsk->cputime_expires.virt_exp = t->expires.cpu;
 			break;
 		}
@@ -1009,20 +990,19 @@ static u32 onecputick;
 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 			     cputime_t *expires, cputime_t cur_time, int signo)
 {
-	if (cputime_eq(it->expires, cputime_zero))
+	if (!it->expires)
 		return;
 
-	if (cputime_ge(cur_time, it->expires)) {
-		if (!cputime_eq(it->incr, cputime_zero)) {
-			it->expires = cputime_add(it->expires, it->incr);
+	if (cur_time >= it->expires) {
+		if (it->incr) {
+			it->expires += it->incr;
 			it->error += it->incr_error;
 			if (it->error >= onecputick) {
-				it->expires = cputime_sub(it->expires,
-							  cputime_one_jiffy);
+				it->expires -= cputime_one_jiffy;
 				it->error -= onecputick;
 			}
 		} else {
-			it->expires = cputime_zero;
+			it->expires = 0;
 		}
 
 		trace_itimer_expire(signo == SIGPROF ?
@@ -1031,9 +1011,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
 	}
 
-	if (!cputime_eq(it->expires, cputime_zero) &&
-	    (cputime_eq(*expires, cputime_zero) ||
-	     cputime_lt(it->expires, *expires))) {
+	if (it->expires && (!*expires || it->expires < *expires)) {
 		*expires = it->expires;
 	}
 }
@@ -1048,9 +1026,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
  */
 static inline int task_cputime_zero(const struct task_cputime *cputime)
 {
-	if (cputime_eq(cputime->utime, cputime_zero) &&
-	    cputime_eq(cputime->stime, cputime_zero) &&
-	    cputime->sum_exec_runtime == 0)
+	if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
 		return 1;
 	return 0;
 }
@@ -1076,15 +1052,15 @@ static void check_process_timers(struct task_struct *tsk,
 	 */
 	thread_group_cputimer(tsk, &cputime);
 	utime = cputime.utime;
-	ptime = cputime_add(utime, cputime.stime);
+	ptime = utime + cputime.stime;
 	sum_sched_runtime = cputime.sum_exec_runtime;
 	maxfire = 20;
-	prof_expires = cputime_zero;
+	prof_expires = 0;
 	while (!list_empty(timers)) {
 		struct cpu_timer_list *tl = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
+		if (!--maxfire || ptime < tl->expires.cpu) {
 			prof_expires = tl->expires.cpu;
 			break;
 		}
@@ -1094,12 +1070,12 @@ static void check_process_timers(struct task_struct *tsk,
 
 	++timers;
 	maxfire = 20;
-	virt_expires = cputime_zero;
+	virt_expires = 0;
 	while (!list_empty(timers)) {
 		struct cpu_timer_list *tl = list_first_entry(timers,
 						      struct cpu_timer_list,
 						      entry);
-		if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
+		if (!--maxfire || utime < tl->expires.cpu) {
 			virt_expires = tl->expires.cpu;
 			break;
 		}
@@ -1154,8 +1130,7 @@ static void check_process_timers(struct task_struct *tsk,
 			}
 		}
 		x = secs_to_cputime(soft);
-		if (cputime_eq(prof_expires, cputime_zero) ||
-		    cputime_lt(x, prof_expires)) {
+		if (!prof_expires || x < prof_expires) {
 			prof_expires = x;
 		}
 	}
@@ -1249,12 +1224,9 @@ out:
 static inline int task_cputime_expired(const struct task_cputime *sample,
 					const struct task_cputime *expires)
 {
-	if (!cputime_eq(expires->utime, cputime_zero) &&
-	    cputime_ge(sample->utime, expires->utime))
+	if (expires->utime && sample->utime >= expires->utime)
 		return 1;
-	if (!cputime_eq(expires->stime, cputime_zero) &&
-	    cputime_ge(cputime_add(sample->utime, sample->stime),
-		       expires->stime))
+	if (expires->stime && sample->utime + sample->stime >= expires->stime)
 		return 1;
 	if (expires->sum_exec_runtime != 0 &&
 	    sample->sum_exec_runtime >= expires->sum_exec_runtime)
@@ -1389,18 +1361,18 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
 		 * it to be relative, *newval argument is relative and we update
 		 * it to be absolute.
 		 */
-		if (!cputime_eq(*oldval, cputime_zero)) {
-			if (cputime_le(*oldval, now.cpu)) {
+		if (*oldval) {
+			if (*oldval <= now.cpu) {
 				/* Just about to fire. */
 				*oldval = cputime_one_jiffy;
 			} else {
-				*oldval = cputime_sub(*oldval, now.cpu);
+				*oldval -= now.cpu;
 			}
 		}
 
-		if (cputime_eq(*newval, cputime_zero))
+		if (!*newval)
 			return;
-		*newval = cputime_add(*newval, now.cpu);
+		*newval += now.cpu;
 	}
 
 	/*
diff --git a/kernel/sched.c b/kernel/sched.c
index d6b149ccf925..18cad4467e61 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2166,7 +2166,7 @@ static int irqtime_account_hi_update(void)
 
 	local_irq_save(flags);
 	latest_ns = this_cpu_read(cpu_hardirq_time);
-	if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->irq))
+	if (nsecs_to_cputime64(latest_ns) > cpustat->irq)
 		ret = 1;
 	local_irq_restore(flags);
 	return ret;
@@ -2181,7 +2181,7 @@ static int irqtime_account_si_update(void)
 
 	local_irq_save(flags);
 	latest_ns = this_cpu_read(cpu_softirq_time);
-	if (cputime64_gt(nsecs_to_cputime64(latest_ns), cpustat->softirq))
+	if (nsecs_to_cputime64(latest_ns) > cpustat->softirq)
 		ret = 1;
 	local_irq_restore(flags);
 	return ret;
@@ -3868,19 +3868,17 @@ void account_user_time(struct task_struct *p, cputime_t cputime,
 		       cputime_t cputime_scaled)
 {
 	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
-	cputime64_t tmp;
 
 	/* Add user time to process. */
-	p->utime = cputime_add(p->utime, cputime);
-	p->utimescaled = cputime_add(p->utimescaled, cputime_scaled);
+	p->utime += cputime;
+	p->utimescaled += cputime_scaled;
 	account_group_user_time(p, cputime);
 
 	/* Add user time to cpustat. */
-	tmp = cputime_to_cputime64(cputime);
 	if (TASK_NICE(p) > 0)
-		cpustat->nice = cputime64_add(cpustat->nice, tmp);
+		cpustat->nice += (__force cputime64_t) cputime;
 	else
-		cpustat->user = cputime64_add(cpustat->user, tmp);
+		cpustat->user += (__force cputime64_t) cputime;
 
 	cpuacct_update_stats(p, CPUACCT_STAT_USER, cputime);
 	/* Account for user time used */
@@ -3896,24 +3894,21 @@ void account_user_time(struct task_struct *p, cputime_t cputime,
 static void account_guest_time(struct task_struct *p, cputime_t cputime,
 			       cputime_t cputime_scaled)
 {
-	cputime64_t tmp;
 	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
 
-	tmp = cputime_to_cputime64(cputime);
-
 	/* Add guest time to process. */
-	p->utime = cputime_add(p->utime, cputime);
-	p->utimescaled = cputime_add(p->utimescaled, cputime_scaled);
+	p->utime += cputime;
+	p->utimescaled += cputime_scaled;
 	account_group_user_time(p, cputime);
-	p->gtime = cputime_add(p->gtime, cputime);
+	p->gtime += cputime;
 
 	/* Add guest time to cpustat. */
 	if (TASK_NICE(p) > 0) {
-		cpustat->nice = cputime64_add(cpustat->nice, tmp);
-		cpustat->guest_nice = cputime64_add(cpustat->guest_nice, tmp);
+		cpustat->nice += (__force cputime64_t) cputime;
+		cpustat->guest_nice += (__force cputime64_t) cputime;
 	} else {
-		cpustat->user = cputime64_add(cpustat->user, tmp);
-		cpustat->guest = cputime64_add(cpustat->guest, tmp);
+		cpustat->user += (__force cputime64_t) cputime;
+		cpustat->guest += (__force cputime64_t) cputime;
 	}
 }
 
@@ -3928,15 +3923,13 @@ static inline
 void __account_system_time(struct task_struct *p, cputime_t cputime,
 			cputime_t cputime_scaled, cputime64_t *target_cputime64)
 {
-	cputime64_t tmp = cputime_to_cputime64(cputime);
-
 	/* Add system time to process. */
-	p->stime = cputime_add(p->stime, cputime);
-	p->stimescaled = cputime_add(p->stimescaled, cputime_scaled);
+	p->stime += cputime;
+	p->stimescaled += cputime_scaled;
 	account_group_system_time(p, cputime);
 
 	/* Add system time to cpustat. */
-	*target_cputime64 = cputime64_add(*target_cputime64, tmp);
+	*target_cputime64 += (__force cputime64_t) cputime;
 	cpuacct_update_stats(p, CPUACCT_STAT_SYSTEM, cputime);
 
 	/* Account for system time used */
@@ -3978,9 +3971,8 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
 void account_steal_time(cputime_t cputime)
 {
 	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
-	cputime64_t cputime64 = cputime_to_cputime64(cputime);
 
-	cpustat->steal = cputime64_add(cpustat->steal, cputime64);
+	cpustat->steal += (__force cputime64_t) cputime;
 }
 
 /*
@@ -3990,13 +3982,12 @@ void account_steal_time(cputime_t cputime)
 void account_idle_time(cputime_t cputime)
 {
 	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
-	cputime64_t cputime64 = cputime_to_cputime64(cputime);
 	struct rq *rq = this_rq();
 
 	if (atomic_read(&rq->nr_iowait) > 0)
-		cpustat->iowait = cputime64_add(cpustat->iowait, cputime64);
+		cpustat->iowait += (__force cputime64_t) cputime;
 	else
-		cpustat->idle = cputime64_add(cpustat->idle, cputime64);
+		cpustat->idle += (__force cputime64_t) cputime;
 }
 
 static __always_inline bool steal_account_process_tick(void)
@@ -4046,16 +4037,15 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
 						struct rq *rq)
 {
 	cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
-	cputime64_t tmp = cputime_to_cputime64(cputime_one_jiffy);
 	struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
 
 	if (steal_account_process_tick())
 		return;
 
 	if (irqtime_account_hi_update()) {
-		cpustat->irq = cputime64_add(cpustat->irq, tmp);
+		cpustat->irq += (__force cputime64_t) cputime_one_jiffy;
 	} else if (irqtime_account_si_update()) {
-		cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
+		cpustat->softirq += (__force cputime64_t) cputime_one_jiffy;
 	} else if (this_cpu_ksoftirqd() == p) {
 		/*
 		 * ksoftirqd time do not get accounted in cpu_softirq_time.
@@ -4171,7 +4161,7 @@ void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 
 void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 {
-	cputime_t rtime, utime = p->utime, total = cputime_add(utime, p->stime);
+	cputime_t rtime, utime = p->utime, total = utime + p->stime;
 
 	/*
 	 * Use CFS's precise accounting:
@@ -4179,11 +4169,11 @@ void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 	rtime = nsecs_to_cputime(p->se.sum_exec_runtime);
 
 	if (total) {
-		u64 temp = rtime;
+		u64 temp = (__force u64) rtime;
 
-		temp *= utime;
-		do_div(temp, total);
-		utime = (cputime_t)temp;
+		temp *= (__force u64) utime;
+		do_div(temp, (__force u32) total);
+		utime = (__force cputime_t) temp;
 	} else
 		utime = rtime;
 
@@ -4191,7 +4181,7 @@ void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 	 * Compare with previous values, to keep monotonicity:
 	 */
 	p->prev_utime = max(p->prev_utime, utime);
-	p->prev_stime = max(p->prev_stime, cputime_sub(rtime, p->prev_utime));
+	p->prev_stime = max(p->prev_stime, rtime - p->prev_utime);
 
 	*ut = p->prev_utime;
 	*st = p->prev_stime;
@@ -4208,21 +4198,20 @@ void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 
 	thread_group_cputime(p, &cputime);
 
-	total = cputime_add(cputime.utime, cputime.stime);
+	total = cputime.utime + cputime.stime;
 	rtime = nsecs_to_cputime(cputime.sum_exec_runtime);
 
 	if (total) {
-		u64 temp = rtime;
+		u64 temp = (__force u64) rtime;
 
-		temp *= cputime.utime;
-		do_div(temp, total);
-		utime = (cputime_t)temp;
+		temp *= (__force u64) cputime.utime;
+		do_div(temp, (__force u32) total);
+		utime = (__force cputime_t) temp;
 	} else
 		utime = rtime;
 
 	sig->prev_utime = max(sig->prev_utime, utime);
-	sig->prev_stime = max(sig->prev_stime,
-			      cputime_sub(rtime, sig->prev_utime));
+	sig->prev_stime = max(sig->prev_stime, rtime - sig->prev_utime);
 
 	*ut = sig->prev_utime;
 	*st = sig->prev_stime;
@@ -9769,7 +9758,8 @@ static void cpuacct_update_stats(struct task_struct *tsk,
 	ca = task_ca(tsk);
 
 	do {
-		__percpu_counter_add(&ca->cpustat[idx], val, batch);
+		__percpu_counter_add(&ca->cpustat[idx],
+				     (__force s64) val, batch);
 		ca = ca->parent;
 	} while (ca);
 	rcu_read_unlock();
diff --git a/kernel/sched_stats.h b/kernel/sched_stats.h
index 87f9e36ea56e..4b71dbef271d 100644
--- a/kernel/sched_stats.h
+++ b/kernel/sched_stats.h
@@ -283,8 +283,7 @@ static inline void account_group_user_time(struct task_struct *tsk,
 		return;
 
 	raw_spin_lock(&cputimer->lock);
-	cputimer->cputime.utime =
-		cputime_add(cputimer->cputime.utime, cputime);
+	cputimer->cputime.utime += cputime;
 	raw_spin_unlock(&cputimer->lock);
 }
 
@@ -307,8 +306,7 @@ static inline void account_group_system_time(struct task_struct *tsk,
 		return;
 
 	raw_spin_lock(&cputimer->lock);
-	cputimer->cputime.stime =
-		cputime_add(cputimer->cputime.stime, cputime);
+	cputimer->cputime.stime += cputime;
 	raw_spin_unlock(&cputimer->lock);
 }
 
diff --git a/kernel/signal.c b/kernel/signal.c
index b3f78d09a105..739ef2bf105c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1629,10 +1629,8 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 	info.si_uid = __task_cred(tsk)->uid;
 	rcu_read_unlock();
 
-	info.si_utime = cputime_to_clock_t(cputime_add(tsk->utime,
-				tsk->signal->utime));
-	info.si_stime = cputime_to_clock_t(cputime_add(tsk->stime,
-				tsk->signal->stime));
+	info.si_utime = cputime_to_clock_t(tsk->utime + tsk->signal->utime);
+	info.si_stime = cputime_to_clock_t(tsk->stime + tsk->signal->stime);
 
 	info.si_status = tsk->exit_code & 0x7f;
 	if (tsk->exit_code & 0x80)
diff --git a/kernel/sys.c b/kernel/sys.c
index 481611fbd079..ddf8155bf3f8 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1605,7 +1605,7 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 	unsigned long maxrss = 0;
 
 	memset((char *) r, 0, sizeof *r);
-	utime = stime = cputime_zero;
+	utime = stime = 0;
 
 	if (who == RUSAGE_THREAD) {
 		task_times(current, &utime, &stime);
@@ -1635,8 +1635,8 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 
 		case RUSAGE_SELF:
 			thread_group_times(p, &tgutime, &tgstime);
-			utime = cputime_add(utime, tgutime);
-			stime = cputime_add(stime, tgstime);
+			utime += tgutime;
+			stime += tgstime;
 			r->ru_nvcsw += p->signal->nvcsw;
 			r->ru_nivcsw += p->signal->nivcsw;
 			r->ru_minflt += p->signal->min_flt;
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index 5bbfac85866e..23b4d784ebdd 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -127,7 +127,7 @@ void acct_update_integrals(struct task_struct *tsk)
 
 		local_irq_save(flags);
 		time = tsk->stime + tsk->utime;
-		dtime = cputime_sub(time, tsk->acct_timexpd);
+		dtime = time - tsk->acct_timexpd;
 		jiffies_to_timeval(cputime_to_jiffies(dtime), &value);
 		delta = value.tv_sec;
 		delta = delta * USEC_PER_SEC + value.tv_usec;