sched, cputime: Cleanups related to task_times()

- Remove if({u,s}t)s because no one call it with NULL now.
- Use cputime_{add,sub}().
- Add ifndef-endif for prev_{u,s}time since they are used
  only when !VIRT_CPU_ACCOUNTING.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Spencer Candland <spencer@bluehost.com>
Cc: Americo Wang <xiyou.wangcong@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
LKML-Reference: <4B1624C7.7040302@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 8 insertions, 10 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 166b8c49257c..ad7cb6d1193c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1066,8 +1066,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->gtime = cputime_zero;
         p->utimescaled = cputime_zero;
         p->stimescaled = cputime_zero;
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
         p->prev_utime = cputime_zero;
         p->prev_stime = cputime_zero;
+#endif
 
         p->default_timer_slack_ns = current->timer_slack_ns;
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 4883fee99314..17e2c1db2bde 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5184,10 +5184,8 @@ void account_idle_ticks(unsigned long ticks)
 #ifdef CONFIG_VIRT_CPU_ACCOUNTING
 void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 {
-        if (ut)
-                *ut = p->utime;
-        if (st)
-                *st = p->stime;
+        *ut = p->utime;
+        *st = p->stime;
 }
 #else
 
@@ -5197,7 +5195,7 @@ void task_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 = utime + p->stime;
+        cputime_t rtime, utime = p->utime, total = cputime_add(utime, p->stime);
 
         /*
          * Use CFS's precise accounting:
@@ -5217,12 +5215,10 @@ 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, rtime - p->prev_utime);
+        p->prev_stime = max(p->prev_stime, cputime_sub(rtime, p->prev_utime));
 
-        if (ut)
-                *ut = p->prev_utime;
-        if (st)
-                *st = p->prev_stime;
+        *ut = p->prev_utime;
+        *st = p->prev_stime;
 }
 #endif