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

This reverts commit 5b7dba4ff8, which
caused a regression in hibernate, reported by and bisected by Fabio
Comolli.

This revert fixes

 http://bugzilla.kernel.org/show_bug.cgi?id=12155
 http://bugzilla.kernel.org/show_bug.cgi?id=12149

Bisected-by: Fabio Comolli <[email protected]>
Requested-by: Rafael J. Wysocki <[email protected]>
Acked-by: Dave Kleikamp <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/sched_clock.c

@@ -118,13 +118,13 @@ static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now)
 
 	/*
 	 * scd->clock = clamp(scd->tick_gtod + delta,
-	 *		      max(scd->tick_gtod, scd->clock),
-	 *		      max(scd->clock, scd->tick_gtod + TICK_NSEC));
+	 * 		      max(scd->tick_gtod, scd->clock),
+	 * 		      scd->tick_gtod + TICK_NSEC);
 	 */
 
 	clock = scd->tick_gtod + delta;
 	min_clock = wrap_max(scd->tick_gtod, scd->clock);
-	max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC);
+	max_clock = scd->tick_gtod + TICK_NSEC;
 
 	clock = wrap_max(clock, min_clock);
 	clock = wrap_min(clock, max_clock);