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authorRoman Zippel <zippel@linux-m68k.org>2008-08-20 16:37:28 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2009-01-24 16:36:24 -0800
commit474f010c78f1d28555971937c1e61688823cb4d1 (patch)
treef3be69e983817bff82ce317bee7269aff74a1a0b /kernel
parentdeee735544d5b34ad4a42ac19abacbfa4d9493f1 (diff)
clocksource: introduce clocksource_forward_now()
commit 9a055117d3d9cb562f83f8d4cd88772761f4cab0 upstream. To keep the raw monotonic patch simple first introduce clocksource_forward_now(), which takes care of the offset since the last update_wall_time() call and adds it to the clock, so there is no need anymore to deal with it explicitly at various places, which need to make significant changes to the clock. This is also gets rid of the timekeeping_suspend_nsecs, instead of waiting until resume, the value is accumulated during suspend. In the end there is only a single user of __get_nsec_offset() left, so I integrated it back to getnstimeofday(). Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/timekeeping.c71
1 files changed, 33 insertions, 38 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4220a2e1faab..521960ba97be 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -61,27 +61,23 @@ struct clocksource *clock;
#ifdef CONFIG_GENERIC_TIME
/**
- * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook
+ * clocksource_forward_now - update clock to the current time
*
- * private function, must hold xtime_lock lock when being
- * called. Returns the number of nanoseconds since the
- * last call to update_wall_time() (adjusted by NTP scaling)
+ * Forward the current clock to update its state since the last call to
+ * update_wall_time(). This is useful before significant clock changes,
+ * as it avoids having to deal with this time offset explicitly.
*/
-static inline s64 __get_nsec_offset(void)
+static void clocksource_forward_now(void)
{
cycle_t cycle_now, cycle_delta;
- s64 ns_offset;
+ s64 nsec;
- /* read clocksource: */
cycle_now = clocksource_read(clock);
-
- /* calculate the delta since the last update_wall_time: */
cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+ clock->cycle_last = cycle_now;
- /* convert to nanoseconds: */
- ns_offset = cyc2ns(clock, cycle_delta);
-
- return ns_offset;
+ nsec = cyc2ns(clock, cycle_delta);
+ timespec_add_ns(&xtime, nsec);
}
/**
@@ -92,6 +88,7 @@ static inline s64 __get_nsec_offset(void)
*/
void getnstimeofday(struct timespec *ts)
{
+ cycle_t cycle_now, cycle_delta;
unsigned long seq;
s64 nsecs;
@@ -101,7 +98,15 @@ void getnstimeofday(struct timespec *ts)
seq = read_seqbegin(&xtime_lock);
*ts = xtime;
- nsecs = __get_nsec_offset();
+
+ /* read clocksource: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs = cyc2ns(clock, cycle_delta);
} while (read_seqretry(&xtime_lock, seq));
@@ -134,22 +139,22 @@ EXPORT_SYMBOL(do_gettimeofday);
*/
int do_settimeofday(struct timespec *tv)
{
+ struct timespec ts_delta;
unsigned long flags;
- time_t wtm_sec, sec = tv->tv_sec;
- long wtm_nsec, nsec = tv->tv_nsec;
if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
return -EINVAL;
write_seqlock_irqsave(&xtime_lock, flags);
- nsec -= __get_nsec_offset();
+ clocksource_forward_now();
+
+ ts_delta.tv_sec = tv->tv_sec - xtime.tv_sec;
+ ts_delta.tv_nsec = tv->tv_nsec - xtime.tv_nsec;
+ wall_to_monotonic = timespec_sub(wall_to_monotonic, ts_delta);
- wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
- wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
+ xtime = *tv;
- set_normalized_timespec(&xtime, sec, nsec);
- set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
update_xtime_cache(0);
clock->error = 0;
@@ -175,22 +180,17 @@ EXPORT_SYMBOL(do_settimeofday);
static void change_clocksource(void)
{
struct clocksource *new;
- cycle_t now;
- u64 nsec;
new = clocksource_get_next();
if (clock == new)
return;
- new->cycle_last = 0;
- now = clocksource_read(new);
- nsec = __get_nsec_offset();
- timespec_add_ns(&xtime, nsec);
+ clocksource_forward_now();
clock = new;
- clock->cycle_last = now;
-
+ clock->cycle_last = 0;
+ clock->cycle_last = clocksource_read(new);
clock->error = 0;
clock->xtime_nsec = 0;
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
@@ -205,8 +205,8 @@ static void change_clocksource(void)
*/
}
#else
+static inline void clocksource_forward_now(void) { }
static inline void change_clocksource(void) { }
-static inline s64 __get_nsec_offset(void) { return 0; }
#endif
/**
@@ -268,8 +268,6 @@ void __init timekeeping_init(void)
/* time in seconds when suspend began */
static unsigned long timekeeping_suspend_time;
-/* xtime offset when we went into suspend */
-static s64 timekeeping_suspend_nsecs;
/**
* timekeeping_resume - Resumes the generic timekeeping subsystem.
@@ -295,8 +293,6 @@ static int timekeeping_resume(struct sys_device *dev)
wall_to_monotonic.tv_sec -= sleep_length;
total_sleep_time += sleep_length;
}
- /* Make sure that we have the correct xtime reference */
- timespec_add_ns(&xtime, timekeeping_suspend_nsecs);
update_xtime_cache(0);
/* re-base the last cycle value */
clock->cycle_last = 0;
@@ -322,8 +318,7 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
timekeeping_suspend_time = read_persistent_clock();
write_seqlock_irqsave(&xtime_lock, flags);
- /* Get the current xtime offset */
- timekeeping_suspend_nsecs = __get_nsec_offset();
+ clocksource_forward_now();
timekeeping_suspended = 1;
write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -464,10 +459,10 @@ void update_wall_time(void)
*/
while (offset >= clock->cycle_interval) {
/* accumulate one interval */
- clock->xtime_nsec += clock->xtime_interval;
- clock->cycle_last += clock->cycle_interval;
offset -= clock->cycle_interval;
+ clock->cycle_last += clock->cycle_interval;
+ clock->xtime_nsec += clock->xtime_interval;
if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
xtime.tv_sec++;