1 files changed, 20 insertions, 0 deletions
diff --git a/include/linux/times.h b/include/linux/times.h
index ff00f334ffaa..0c5aa078dad4 100644
--- a/include/linux/times.h
+++ b/include/linux/times.h
@@ -55,6 +55,26 @@ static inline u64 jiffies_64_to_clock_t(u64 x)
 }
 #endif
 
+static inline u64 nsec_to_clock_t(u64 x)
+{
+#if (NSEC_PER_SEC % USER_HZ) == 0
+	do_div(x, (NSEC_PER_SEC / USER_HZ));
+#elif (USER_HZ % 512) == 0
+	x *= USER_HZ/512;
+	do_div(x, (NSEC_PER_SEC / 512));
+#else
+	/*
+         * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024,
+         * overflow after 64.99 years.
+         * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ...
+         */
+	x *= 9;
+	do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2))
+	                          / USER_HZ));
+#endif
+	return x;
+}
+
 struct tms {
 	clock_t tms_utime;
 	clock_t tms_stime;