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sched_clock: prevent scd->clock from moving backwards, take #2

Browse source 
Redo:

  5b7dba4: sched_clock: prevent scd->clock from moving backwards

which had to be reverted due to s2ram hangs:

  ca7e716: Revert "sched_clock: prevent scd->clock from moving backwards"

... this time with resume restoring GTOD later in the sequence
taken into account as well.

The "timekeeping_suspended" flag is not very nice but we cannot call into
GTOD before it has been properly resumed and the scheduler will run very
early in the resume sequence.

Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner 2008-12-22 23:05:28 +01:00 committed by Ingo Molnar
parent 6a94cb7306
commit 1c5745aa38
3 changed files with 10 additions and 3 deletions
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1
include/linux/time.h
View file

@ -105,6 +105,7 @@ extern unsigned long read_persistent_clock(void);
extern int update_persistent_clock(struct timespec now);
extern int no_sync_cmos_clock __read_mostly;
void timekeeping_init(void);
extern int timekeeping_suspended;
unsigned long get_seconds(void);
struct timespec current_kernel_time(void);

5
kernel/sched_clock.c
View file

@ -124,7 +124,7 @@ static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now)
clock = scd->tick_gtod + delta;
min_clock = wrap_max(scd->tick_gtod, scd->clock);
max_clock = scd->tick_gtod + TICK_NSEC;
max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC);
clock = wrap_max(clock, min_clock);
clock = wrap_min(clock, max_clock);
@ -227,6 +227,9 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
*/
void sched_clock_idle_wakeup_event(u64 delta_ns)
{
if (timekeeping_suspended)
return;
sched_clock_tick();
touch_softlockup_watchdog();
}

7
kernel/time/timekeeping.c
View file

@ -46,6 +46,9 @@ struct timespec xtime __attribute__ ((aligned (16)));
struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
static unsigned long total_sleep_time; /* seconds */
/* 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)
{
@ -92,6 +95,8 @@ void getnstimeofday(struct timespec *ts)
unsigned long seq;
s64 nsecs;
WARN_ON(timekeeping_suspended);
do {
seq = read_seqbegin(&xtime_lock);
@ -299,8 +304,6 @@ void __init timekeeping_init(void)
write_sequnlock_irqrestore(&xtime_lock, flags);
}
/* flag for if timekeeping is suspended */
static int timekeeping_suspended;
/* time in seconds when suspend began */
static unsigned long timekeeping_suspend_time;