sched: cleanup, use NSEC_PER_MSEC and NSEC_PER_SEC

1) hardcoded 1000000000 value is used five times in places where
   NSEC_PER_SEC might be more readable.

2) A conversion from nsec to msec uses the hardcoded 1000000 value,
   which is a candidate for NSEC_PER_MSEC.

no code changed:

    text    data     bss     dec     hex filename
   44359    3326      36   47721    ba69 sched.o.before
   44359    3326      36   47721    ba69 sched.o.after

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched.c

@@ -75,7 +75,7 @@
  */
 unsigned long long __attribute__((weak)) sched_clock(void)
 {
-	return (unsigned long long)jiffies * (1000000000 / HZ);
+	return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
 }
 
 /*
@@ -99,8 +99,8 @@ unsigned long long __attribute__((weak)) sched_clock(void)
 /*
  * Some helpers for converting nanosecond timing to jiffy resolution
  */
-#define NS_TO_JIFFIES(TIME)	((unsigned long)(TIME) / (1000000000 / HZ))
-#define JIFFIES_TO_NS(TIME)	((TIME) * (1000000000 / HZ))
+#define NS_TO_JIFFIES(TIME)	((unsigned long)(TIME) / (NSEC_PER_SEC / HZ))
+#define JIFFIES_TO_NS(TIME)	((TIME) * (NSEC_PER_SEC / HZ))
 
 #define NICE_0_LOAD		SCHED_LOAD_SCALE
 #define NICE_0_SHIFT		SCHED_LOAD_SHIFT
@@ -7256,7 +7256,7 @@ static u64 cpu_usage_read(struct cgroup *cgrp, struct cftype *cft)
 		spin_unlock_irqrestore(&cpu_rq(i)->lock, flags);
 	}
 	/* Convert from ns to ms */
-	do_div(res, 1000000);
+	do_div(res, NSEC_PER_MSEC);
 
 	return res;
 }

kernel/sysctl.c

@@ -226,9 +226,9 @@ static struct ctl_table root_table[] = {
 
 #ifdef CONFIG_SCHED_DEBUG
 static unsigned long min_sched_granularity_ns = 100000;		/* 100 usecs */
-static unsigned long max_sched_granularity_ns = 1000000000;	/* 1 second */
+static unsigned long max_sched_granularity_ns = NSEC_PER_SEC;	/* 1 second */
 static unsigned long min_wakeup_granularity_ns;			/* 0 usecs */
-static unsigned long max_wakeup_granularity_ns = 1000000000;	/* 1 second */
+static unsigned long max_wakeup_granularity_ns = NSEC_PER_SEC;	/* 1 second */
 #endif
 
 static struct ctl_table kern_table[] = {