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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2009-08-14 15:47:31 +0200
committerThomas Gleixner <tglx@linutronix.de>2009-08-15 10:55:46 +0200
commitd4f587c67fc39e0030ddd718675e252e208da4d7 (patch)
tree2222681c57966cc6b8404afdff3ab1a09ac7ea69 /kernel
parent75c5158f70c065b9704b924503d96e8297838f79 (diff)
downloadop-kernel-dev-d4f587c67fc39e0030ddd718675e252e208da4d7.zip
op-kernel-dev-d4f587c67fc39e0030ddd718675e252e208da4d7.tar.gz
timekeeping: Increase granularity of read_persistent_clock()
The persistent clock of some architectures (e.g. s390) have a better granularity than seconds. To reduce the delta between the host clock and the guest clock in a virtualized system change the read_persistent_clock function to return a struct timespec. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Acked-by: John Stultz <johnstul@us.ibm.com> Cc: Daniel Walker <dwalker@fifo99.com> LKML-Reference: <20090814134811.013873340@de.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/timekeeping.c52
1 files changed, 29 insertions, 23 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 41579e7..f1a21ce 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -154,7 +154,7 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
*/
struct timespec xtime __attribute__ ((aligned (16)));
struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
-static unsigned long total_sleep_time; /* seconds */
+static struct timespec total_sleep_time;
/*
* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock.
@@ -487,17 +487,18 @@ int timekeeping_valid_for_hres(void)
}
/**
- * read_persistent_clock - Return time in seconds from the persistent clock.
+ * read_persistent_clock - Return time from the persistent clock.
*
* Weak dummy function for arches that do not yet support it.
- * Returns seconds from epoch using the battery backed persistent clock.
- * Returns zero if unsupported.
+ * Reads the time from the battery backed persistent clock.
+ * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
*
* XXX - Do be sure to remove it once all arches implement it.
*/
-unsigned long __attribute__((weak)) read_persistent_clock(void)
+void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
{
- return 0;
+ ts->tv_sec = 0;
+ ts->tv_nsec = 0;
}
/*
@@ -507,7 +508,9 @@ void __init timekeeping_init(void)
{
struct clocksource *clock;
unsigned long flags;
- unsigned long sec = read_persistent_clock();
+ struct timespec now;
+
+ read_persistent_clock(&now);
write_seqlock_irqsave(&xtime_lock, flags);
@@ -518,19 +521,20 @@ void __init timekeeping_init(void)
clock->enable(clock);
timekeeper_setup_internals(clock);
- xtime.tv_sec = sec;
- xtime.tv_nsec = 0;
+ xtime.tv_sec = now.tv_sec;
+ xtime.tv_nsec = now.tv_nsec;
raw_time.tv_sec = 0;
raw_time.tv_nsec = 0;
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
update_xtime_cache(0);
- total_sleep_time = 0;
+ total_sleep_time.tv_sec = 0;
+ total_sleep_time.tv_nsec = 0;
write_sequnlock_irqrestore(&xtime_lock, flags);
}
/* time in seconds when suspend began */
-static unsigned long timekeeping_suspend_time;
+static struct timespec timekeeping_suspend_time;
/**
* timekeeping_resume - Resumes the generic timekeeping subsystem.
@@ -543,18 +547,19 @@ static unsigned long timekeeping_suspend_time;
static int timekeeping_resume(struct sys_device *dev)
{
unsigned long flags;
- unsigned long now = read_persistent_clock();
+ struct timespec ts;
+
+ read_persistent_clock(&ts);
clocksource_resume();
write_seqlock_irqsave(&xtime_lock, flags);
- if (now && (now > timekeeping_suspend_time)) {
- unsigned long sleep_length = now - timekeeping_suspend_time;
-
- xtime.tv_sec += sleep_length;
- wall_to_monotonic.tv_sec -= sleep_length;
- total_sleep_time += sleep_length;
+ if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
+ ts = timespec_sub(ts, timekeeping_suspend_time);
+ xtime = timespec_add_safe(xtime, ts);
+ wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
+ total_sleep_time = timespec_add_safe(total_sleep_time, ts);
}
update_xtime_cache(0);
/* re-base the last cycle value */
@@ -577,7 +582,7 @@ static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
{
unsigned long flags;
- timekeeping_suspend_time = read_persistent_clock();
+ read_persistent_clock(&timekeeping_suspend_time);
write_seqlock_irqsave(&xtime_lock, flags);
timekeeping_forward_now();
@@ -801,9 +806,10 @@ void update_wall_time(void)
*/
void getboottime(struct timespec *ts)
{
- set_normalized_timespec(ts,
- - (wall_to_monotonic.tv_sec + total_sleep_time),
- - wall_to_monotonic.tv_nsec);
+ struct timespec boottime;
+
+ boottime = timespec_add_safe(wall_to_monotonic, total_sleep_time);
+ set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
}
/**
@@ -812,7 +818,7 @@ void getboottime(struct timespec *ts)
*/
void monotonic_to_bootbased(struct timespec *ts)
{
- ts->tv_sec += total_sleep_time;
+ *ts = timespec_add_safe(*ts, total_sleep_time);
}
unsigned long get_seconds(void)
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