From: Christoph Lameter <clameter@sgi.com>
This issue was discussed on lkml and linux-ia64. The patch introduces
"getnstimeofday" and removes all the code scaling gettimeofday to
nanoseoncs. It makes it possible for the posix-timer functions to return
higher accuracy.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/linux/time.h | 1 +
25-akpm/kernel/posix-timers.c | 17 ++---------------
25-akpm/kernel/time.c | 38 ++++++++++++++++++++++++++++++++++++++
25-akpm/kernel/timer.c | 3 +--
4 files changed, 42 insertions(+), 17 deletions(-)
diff -puN include/linux/time.h~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer include/linux/time.h
--- 25/include/linux/time.h~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer 2004-07-26 15:20:23.830526848 -0700
+++ 25-akpm/include/linux/time.h 2004-07-26 15:20:23.840525328 -0700
@@ -348,6 +348,7 @@ extern long do_utimes(char __user * file
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);
static inline void
set_normalized_timespec (struct timespec *ts, time_t sec, long nsec)
diff -puN kernel/posix-timers.c~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer kernel/posix-timers.c
--- 25/kernel/posix-timers.c~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer 2004-07-26 15:20:23.832526544 -0700
+++ 25-akpm/kernel/posix-timers.c 2004-07-26 15:20:23.840525328 -0700
@@ -1168,15 +1168,10 @@ void exit_itimers(struct signal_struct *
*/
static int do_posix_gettime(struct k_clock *clock, struct timespec *tp)
{
- struct timeval tv;
-
if (clock->clock_get)
return clock->clock_get(tp);
- do_gettimeofday(&tv);
- tp->tv_sec = tv.tv_sec;
- tp->tv_nsec = tv.tv_usec * NSEC_PER_USEC;
-
+ getnstimeofday(tp);
return 0;
}
@@ -1192,24 +1187,16 @@ static u64 do_posix_clock_monotonic_gett
struct timespec *tp, struct timespec *mo)
{
u64 jiff;
- struct timeval tpv;
unsigned int seq;
do {
seq = read_seqbegin(&xtime_lock);
- do_gettimeofday(&tpv);
+ getnstimeofday(tp);
*mo = wall_to_monotonic;
jiff = jiffies_64;
} while(read_seqretry(&xtime_lock, seq));
- /*
- * Love to get this before it is converted to usec.
- * It would save a div AND a mpy.
- */
- tp->tv_sec = tpv.tv_sec;
- tp->tv_nsec = tpv.tv_usec * NSEC_PER_USEC;
-
return jiff;
}
diff -puN kernel/time.c~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer kernel/time.c
--- 25/kernel/time.c~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer 2004-07-26 15:20:23.833526392 -0700
+++ 25-akpm/kernel/time.c 2004-07-26 15:20:23.841525176 -0700
@@ -22,6 +22,9 @@
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10)
* (Even though the technical memorandum forbids it)
+ * 2004-07-14 Christoph Lameter
+ * Added getnstimeofday to allow the posix timer functions to return
+ * with nanosecond accuracy
*/
#include <linux/module.h>
@@ -421,6 +424,41 @@ struct timespec current_kernel_time(void
EXPORT_SYMBOL(current_kernel_time);
+#ifdef CONFIG_TIME_INTERPOLATION
+void getnstimeofday (struct timespec *tv)
+{
+ unsigned long seq,sec,nsec;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ sec = xtime.tv_sec;
+ nsec = xtime.tv_nsec+time_interpolator_get_offset();
+ } while (unlikely(read_seqretry(&xtime_lock, seq)));
+
+ while (unlikely(nsec >= NSEC_PER_SEC)) {
+ nsec -= NSEC_PER_SEC;
+ ++sec;
+ }
+ tv->tv_sec = sec;
+ tv->tv_nsec = nsec;
+}
+#else
+/*
+ * Simulate gettimeofday using do_gettimeofday which only allows a timeval
+ * and therefore only yields usec accuracy
+ */
+void getnstimeofday(struct timespec *tv)
+{
+ struct timeval x;
+
+ do_gettimeofday(&x);
+ tv->tv_sec = x.tv_sec;
+ tv->tv_nsec = x.tv_usec * NSEC_PER_USEC;
+}
+#endif
+
+EXPORT_SYMBOL(getnstimeofday);
+
#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void)
{
diff -puN kernel/timer.c~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer kernel/timer.c
--- 25/kernel/timer.c~gettimeofday-nanoseconds-patch-makes-it-possible-for-the-posix-timer 2004-07-26 15:20:23.835526088 -0700
+++ 25-akpm/kernel/timer.c 2004-07-26 15:20:23.839525480 -0700
@@ -1243,8 +1243,7 @@ asmlinkage long sys_sysinfo(struct sysin
* too.
*/
- do_gettimeofday((struct timeval *)&tp);
- tp.tv_nsec *= NSEC_PER_USEC;
+ getnstimeofday(&tp);
tp.tv_sec += wall_to_monotonic.tv_sec;
tp.tv_nsec += wall_to_monotonic.tv_nsec;
if (tp.tv_nsec - NSEC_PER_SEC >= 0) {
_