[Patch 1/7] timespec diff utility

[Shailabh Nagar <nagar@watson.ibm.com>]

nstimestamp_diff.patch

Add kernel utility function for measuring the
interval (diff) between two timespec values, adjusting for overflow

Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>

 include/linux/time.h |   14 ++++++++++++++
 1 files changed, 14 insertions(+)

Index: linux-2.6.16-rc4/include/linux/time.h
===================================================================
--- linux-2.6.16-rc4.orig/include/linux/time.h	2006-02-27 01:20:04.000000000 -0500
+++ linux-2.6.16-rc4/include/linux/time.h	2006-02-27 01:52:49.000000000 -0500
@@ -147,6 +147,20 @@ extern struct timespec ns_to_timespec(co
  */
 extern struct timeval ns_to_timeval(const nsec_t nsec);
 
+/*
+ * timespec_diff_ns - Return difference of two timestamps in nanoseconds
+ * In the rare case of @end being earlier than @start, return zero
+ */
+static inline nsec_t timespec_diff_ns(struct timespec *start, struct timespec *end)
+{
+	nsec_t ret;
+
+	ret = (nsec_t)(end->tv_sec - start->tv_sec)*NSEC_PER_SEC;
+	ret += (nsec_t)(end->tv_nsec - start->tv_nsec);
+	if (ret < 0)
+ 		return 0;
+	return ret;
+}
 #endif /* __KERNEL__ */
 
 #define NFDBITS			__NFDBITS


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