[PATCH] gettimeofday nanoseconds patch

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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/linux/time.h b/include/linux/time.h
index d24a690..de41e12 100644 (file)
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -348,6 +348,7 @@ extern long do_utimes(char __user * filename, struct timeval * times);
 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 --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index 42c2486..f2d93f6 100644 (file)
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -1168,15 +1168,10 @@ void exit_itimers(struct signal_struct *sig)
  */
 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_gettime_parts(
        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 --git a/kernel/time.c b/kernel/time.c
index 68c22f2..b0bdef2 100644 (file)
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -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 --git a/kernel/timer.c b/kernel/timer.c
index 4850abb..79db45d 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1241,8 +1241,7 @@ asmlinkage long sys_sysinfo(struct sysinfo __user *info)
                 * 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) {