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yaml --- r: 169913 b: refs/heads/master c: b7b20df h: refs/heads/master i: 169911: 66874cf v: v3
git-mirror · Nov 26, 2009 · 75f3111 · 75f3111
1 parent 586e7fa
commit 75f3111
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Showing 4 changed files with 33 additions and 3 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d5b7c78e975302a1bab28263266c39ecb71acad4
+refs/heads/master: b7b20df91d43d5e59578b8fc16e895c0c8cbd9b5
diff --git a/trunk/include/linux/jiffies.h b/trunk/include/linux/jiffies.h
@@ -307,6 +307,7 @@ extern clock_t jiffies_to_clock_t(long x);
 extern unsigned long clock_t_to_jiffies(unsigned long x);
 extern u64 jiffies_64_to_clock_t(u64 x);
 extern u64 nsec_to_clock_t(u64 x);
+extern unsigned long nsecs_to_jiffies(u64 n);
 
 #define TIMESTAMP_SIZE	30
 

diff --git a/trunk/kernel/sched.c b/trunk/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)

diff --git a/trunk/kernel/time.c b/trunk/kernel/time.c
@@ -662,6 +662,36 @@ u64 nsec_to_clock_t(u64 x)
 #endif
 }
 
+/**
+ * nsecs_to_jiffies - Convert nsecs in u64 to jiffies
+ *
+ * @n:	nsecs in u64
+ *
+ * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64.
+ * And this doesn't return MAX_JIFFY_OFFSET since this function is designed
+ * for scheduler, not for use in device drivers to calculate timeout value.
+ *
+ * note:
+ *   NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512)
+ *   ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years
+ */
+unsigned long nsecs_to_jiffies(u64 n)
+{
+#if (NSEC_PER_SEC % HZ) == 0
+	/* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */
+	return div_u64(n, NSEC_PER_SEC / HZ);
+#elif (HZ % 512) == 0
+	/* overflow after 292 years if HZ = 1024 */
+	return div_u64(n * HZ / 512, NSEC_PER_SEC / 512);
+#else
+	/*
+	 * Generic case - optimized for cases where HZ is a multiple of 3.
+	 * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc.
+	 */
+	return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ);
+#endif
+}
+
 #if (BITS_PER_LONG < 64)
 u64 get_jiffies_64(void)
 {