Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 64123fd4 authored by Matt Helsley's avatar Matt Helsley Committed by Linus Torvalds
Browse files

[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: default avatarMatt Helsley <matthltc@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 894ec870

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)

{