[PATCH] Add getnstimestamp function
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>
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@ -95,6 +95,7 @@ struct itimerval;
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extern int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue);
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extern int do_getitimer(int which, struct itimerval *value);
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extern void getnstimeofday (struct timespec *tv);
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extern void getnstimestamp(struct timespec *ts);
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extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
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@ -561,6 +561,28 @@ void getnstimeofday(struct timespec *tv)
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EXPORT_SYMBOL_GPL(getnstimeofday);
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#endif
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void getnstimestamp(struct timespec *ts)
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{
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unsigned int seq;
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struct timespec wall2mono;
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/* synchronize with settimeofday() changes */
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do {
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seq = read_seqbegin(&xtime_lock);
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getnstimeofday(ts);
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wall2mono = wall_to_monotonic;
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} while(unlikely(read_seqretry(&xtime_lock, seq)));
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/* adjust to monotonicaly-increasing values */
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ts->tv_sec += wall2mono.tv_sec;
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ts->tv_nsec += wall2mono.tv_nsec;
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while (unlikely(ts->tv_nsec >= NSEC_PER_SEC)) {
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ts->tv_nsec -= NSEC_PER_SEC;
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ts->tv_sec++;
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}
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}
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EXPORT_SYMBOL_GPL(getnstimestamp);
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#if (BITS_PER_LONG < 64)
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u64 get_jiffies_64(void)
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{
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