sched, time: Define nsecs_to_jiffies()

Use of msecs_to_jiffies() for nsecs_to_cputime() have some
problems:

 - The type of msecs_to_jiffies()'s argument is unsigned int, so
   it cannot convert msecs greater than UINT_MAX = about 49.7 days.

 - msecs_to_jiffies() returns MAX_JIFFY_OFFSET if MSB of argument
   is set, assuming that input was negative value.  So it cannot
   convert msecs greater than INT_MAX = about 24.8 days too.

This patch defines a new function nsecs_to_jiffies() that can
deal greater values, and that can deal all incoming values as
unsigned.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Spencer Candland <spencer@bluehost.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Amrico Wang <xiyou.wangcong@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <johnstul@linux.vnet.ibm.com>
LKML-Reference: <4B0E16E7.5070307@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 2 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 82251c21f785..b3d4e2be95aa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5192,8 +5192,7 @@ void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)
 #else
 
 #ifndef nsecs_to_cputime
-# define nsecs_to_cputime(__nsecs) \
-        msecs_to_cputime(div_u64((__nsecs), NSEC_PER_MSEC))
+# define nsecs_to_cputime(__nsecs)      nsecs_to_jiffies(__nsecs)
 #endif
 
 void task_times(struct task_struct *p, cputime_t *ut, cputime_t *st)