[PATCH] Add getnstimestamp function (64123fd4) · Commits · 戴 / test

There are several functions that might seem appropriate for a timestamp: get_cycles() current_kernel_time() do_gettimeofday() <read jiffies/jiffies_64> Each has problems with combinations of SMP-safety, low resolution, and monotonicity. This patch adds a new function that returns a monotonic SMP-safe timestamp with nanosecond resolution where available. Changes: Split timestamp into separate patch Moved to kernel/time.c Renamed to getnstimestamp Fixed unintended-pointer-arithmetic bug Signed-off-by:

Matt Helsley <matthltc@us.ibm.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

include/linux/time.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -95,6 +95,7 @@ struct itimerval;
		extern int do_setitimer(int which, struct itimerval value, struct itimerval ovalue);
		extern int do_getitimer(int which, struct itimerval *value);
		extern void getnstimeofday (struct timespec *tv);
		extern void getnstimestamp(struct timespec *ts);

		extern struct timespec timespec_trunc(struct timespec t, unsigned gran);

kernel/time.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -561,6 +561,28 @@ void getnstimeofday(struct timespec *tv)
		EXPORT_SYMBOL_GPL(getnstimeofday);
		#endif

		void getnstimestamp(struct timespec *ts)
		{
		unsigned int seq;
		struct timespec wall2mono;

		/* synchronize with settimeofday() changes */
		do {
		seq = read_seqbegin(&xtime_lock);
		getnstimeofday(ts);
		wall2mono = wall_to_monotonic;
		} while(unlikely(read_seqretry(&xtime_lock, seq)));

		/* adjust to monotonicaly-increasing values */
		ts->tv_sec += wall2mono.tv_sec;
		ts->tv_nsec += wall2mono.tv_nsec;
		while (unlikely(ts->tv_nsec >= NSEC_PER_SEC)) {
		ts->tv_nsec -= NSEC_PER_SEC;
		ts->tv_sec++;
		}
		}
		EXPORT_SYMBOL_GPL(getnstimestamp);

		#if (BITS_PER_LONG < 64)
		u64 get_jiffies_64(void)
		{

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