The patch titled
clocksource: introduce clocksource_forward_now
has been removed from the -mm tree. Its filename was
clocksource-introduce-clocksource_forward_now.patch
This patch was dropped because an updated version will be merged
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: clocksource: introduce clocksource_forward_now
From: Roman Zippel <zippel@xxxxxxxxxxxxxx>
There is a problem with the time offset since the last update_wall_time()
call, which isn't taken into account when switching clocks (possibly during
suspend/resume too), so that the clock might jump back during a clock switch.
To avoid making the whole more complex it's better to do small cleanup first,
so this patch introduces clocksource_forward_now() which takes care of this
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. This is also gets rid of
the timekeeping_suspend_nsecs hack, 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@xxxxxxxxxxxxxx>
Acked-by: John Stultz <johnstul@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/time/timekeeping.c | 66 ++++++++++++++++--------------------
1 file changed, 30 insertions(+), 36 deletions(-)
diff -puN kernel/time/timekeeping.c~clocksource-introduce-clocksource_forward_now kernel/time/timekeeping.c
--- a/kernel/time/timekeeping.c~clocksource-introduce-clocksource_forward_now
+++ a/kernel/time/timekeeping.c
@@ -59,27 +59,23 @@ 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);
}
/**
@@ -90,6 +86,7 @@ static inline s64 __get_nsec_offset(void
*/
void getnstimeofday(struct timespec *ts)
{
+ cycle_t cycle_now, cycle_delta;
unsigned long seq;
s64 nsecs;
@@ -97,7 +94,15 @@ 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));
@@ -131,21 +136,19 @@ EXPORT_SYMBOL(do_gettimeofday);
int do_settimeofday(struct timespec *tv)
{
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();
- wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
- wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
+ wall_to_monotonic.tv_sec += xtime.tv_sec - tv->tv_sec;
+ timespec_add_ns(&wall_to_monotonic, xtime.tv_nsec - tv->tv_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;
@@ -171,21 +174,16 @@ 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;
- 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 = clocksource_read(new);
clock->error = 0;
clock->xtime_nsec = 0;
clock->raw_snsec = 0;
@@ -201,8 +199,8 @@ 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
/**
@@ -301,8 +299,6 @@ void __init timekeeping_init(void)
static int timekeeping_suspended;
/* 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.
@@ -328,8 +324,6 @@ static int timekeeping_resume(struct sys
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 = clocksource_read(clock);
@@ -354,8 +348,7 @@ static int timekeeping_suspend(struct sy
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);
@@ -497,9 +490,10 @@ void update_wall_time(void)
*/
while (offset >= clock->cycle_interval) {
/* accumulate one interval */
- clock->xtime_nsec += clock->xtime_interval;
clock->raw_snsec += clock->raw_interval;
clock->cycle_last += clock->cycle_interval;
+ clock->xtime_nsec += clock->xtime_interval;
+
offset -= clock->cycle_interval;
if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
_
Patches currently in -mm which might be from zippel@xxxxxxxxxxxxxx are
git-x86.patch
provide-u64-version-of-jiffies_to_usecs-in-kernel-tsacctc.patch
git-watchdog.patch
m68k-replace-remaining-__function__-occurences.patch
fs-hfsplus-proper-externs.patch
affs-handle-match_strdup-failure.patch
hfs-handle-match_strdup-failure.patch
hfsplus-handle-match_strdup-failure.patch
fs-affs-filec-use-bug_on.patch
affs-be_add_cpu-conversion.patch
hfs-hfsplus-be_add_cpu-conversion.patch
hfs-fix-warning-with-64k-page_size.patch
hfsplus-fix-warning-with-64k-page_size.patch
introduce-explicit-signed-unsigned-64bit-divide.patch
convert-a-few-do_div-user.patch
rename-div64_64-to-div64_u64.patch
rename-div64_64-to-div64_u64-mm.patch
remove-div_long_long_rem.patch
ntp-cleanup-ntpc.patch
ntp-ntp4-user-space-bits-update.patch
ntp-increase-time_freq-resolution.patch
ntp-increase-time_offset-resolution.patch
ntp-support-for-tai.patch
ntp-rename-tick_length_shift-to-ntp_scale_shift.patch
ntp-remove-current_tick_length.patch
ntp-handle-leap-second-via-timer.patch
clocksource-introduce-clocksource_forward_now.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
