[PATCH] idle threads should have a sane ->timestamp value

Idle threads should have a sane ->timestamp value, to avoid init kernel
thread(s) from inheriting it and causing miscalculations in
try_to_wake_up().

Reported-by: Mike Galbraith <efault@gmx.de>.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/sched.c

@@ -4335,6 +4335,7 @@ void __devinit init_idle(task_t *idle, int cpu)
 	runqueue_t *rq = cpu_rq(cpu);
 	unsigned long flags;
 
+	idle->timestamp = sched_clock();
 	idle->sleep_avg = 0;
 	idle->array = NULL;
 	idle->prio = MAX_PRIO;