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time: Remove xtime_cache

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With the earlier logarithmic time accumulation patch, xtime will now
always be within one "tick" of the current time, instead of possibly
half a second off.

This removes the need for the xtime_cache value, which always stored the
time at the last interrupt, so this patch cleans that up removing the
xtime_cache related code.

This patch also addresses an issue with an earlier version of this change,
where xtime_cache was normalizing xtime, which could in some cases be
not valid (ie: tv_nsec == NSEC_PER_SEC). This is fixed by handling
the edge case in update_wall_time().

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Petr Titěra <P.Titera@century.cz>
LKML-Reference: <1270589451-30773-1-git-send-email-johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
John Stultz 2010-04-06 14:30:51 -07:00 committed by Thomas Gleixner
parent 9ca7d8e683
commit 6a867a3955
2 changed files with 16 additions and 20 deletions
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1
include/linux/time.h
View File

@ -150,7 +150,6 @@ extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_valid_for_hres(void);
extern u64 timekeeping_max_deferment(void);
extern void update_wall_time(void);
extern void update_xtime_cache(u64 nsec);
extern void timekeeping_leap_insert(int leapsecond);
struct tms;

35
kernel/time/timekeeping.c
View File

@ -165,13 +165,6 @@ struct timespec raw_time;
/* flag for if timekeeping is suspended */
int __read_mostly timekeeping_suspended;
static struct timespec xtime_cache __attribute__ ((aligned (16)));
void update_xtime_cache(u64 nsec)
{
xtime_cache = xtime;
timespec_add_ns(&xtime_cache, nsec);
}
/* must hold xtime_lock */
void timekeeping_leap_insert(int leapsecond)
{
@ -332,8 +325,6 @@ int do_settimeofday(struct timespec *tv)
xtime = *tv;
update_xtime_cache(0);
timekeeper.ntp_error = 0;
ntp_clear();
@ -559,7 +550,6 @@ void __init timekeeping_init(void)
}
set_normalized_timespec(&wall_to_monotonic,
-boot.tv_sec, -boot.tv_nsec);
update_xtime_cache(0);
total_sleep_time.tv_sec = 0;
total_sleep_time.tv_nsec = 0;
write_sequnlock_irqrestore(&xtime_lock, flags);
@ -593,7 +583,6 @@ static int timekeeping_resume(struct sys_device *dev)
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 */
timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
timekeeper.ntp_error = 0;
@ -788,7 +777,6 @@ void update_wall_time(void)
{
struct clocksource *clock;
cycle_t offset;
u64 nsecs;
int shift = 0, maxshift;
/* Make sure we're fully resumed: */
@ -846,7 +834,9 @@ void update_wall_time(void)
timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
}
/* store full nanoseconds into xtime after rounding it up and
/*
* Store full nanoseconds into xtime after rounding it up and
* add the remainder to the error difference.
*/
xtime.tv_nsec = ((s64) timekeeper.xtime_nsec >> timekeeper.shift) + 1;
@ -854,8 +844,15 @@ void update_wall_time(void)
timekeeper.ntp_error += timekeeper.xtime_nsec <<
timekeeper.ntp_error_shift;
nsecs = clocksource_cyc2ns(offset, timekeeper.mult, timekeeper.shift);
update_xtime_cache(nsecs);
/*
* Finally, make sure that after the rounding
* xtime.tv_nsec isn't larger then NSEC_PER_SEC
*/
if (unlikely(xtime.tv_nsec >= NSEC_PER_SEC)) {
xtime.tv_nsec -= NSEC_PER_SEC;
xtime.tv_sec++;
second_overflow();
}
/* check to see if there is a new clocksource to use */
update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
@ -895,13 +892,13 @@ EXPORT_SYMBOL_GPL(monotonic_to_bootbased);
unsigned long get_seconds(void)
{
return xtime_cache.tv_sec;
return xtime.tv_sec;
}
EXPORT_SYMBOL(get_seconds);
struct timespec __current_kernel_time(void)
{
return xtime_cache;
return xtime;
}
struct timespec current_kernel_time(void)
@ -912,7 +909,7 @@ struct timespec current_kernel_time(void)
do {
seq = read_seqbegin(&xtime_lock);
now = xtime_cache;
now = xtime;
} while (read_seqretry(&xtime_lock, seq));
return now;
@ -927,7 +924,7 @@ struct timespec get_monotonic_coarse(void)
do {
seq = read_seqbegin(&xtime_lock);
now = xtime_cache;
now = xtime;
mono = wall_to_monotonic;
} while (read_seqretry(&xtime_lock, seq));