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Subject[patch 11/85] sched_clock: prevent scd->clock from moving backwards, take #2
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Thomas Gleixner <tglx@linutronix.de>

commit 1c5745aa380efb6417b5681104b007c8612fb496 upstream.

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.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
include/linux/time.h | 1 +
kernel/sched_clock.c | 5 ++++-
kernel/time/timekeeping.c | 7 +++++--
3 files changed, 10 insertions(+), 3 deletions(-)

--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -99,6 +99,7 @@ extern unsigned long read_persistent_clo
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);
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -124,7 +124,7 @@ static u64 __update_sched_clock(struct s

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
*/
void sched_clock_idle_wakeup_event(u64 delta_ns)
{
+ if (timekeeping_suspended)
+ return;
+
sched_clock_tick();
touch_softlockup_watchdog();
}
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -46,6 +46,9 @@ struct timespec xtime __attribute__ ((al
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);

@@ -261,8 +266,6 @@ 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;
/* xtime offset when we went into suspend */


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