sched/core: Add missing update_rq_clock() call for task_hot()

Add the update_rq_clock() call at the top of the callstack instead of
at the bottom where we find it missing, this to aid later effort to
minimize the number of update_rq_lock() calls.

  WARNING: CPU: 30 PID: 194 at ../kernel/sched/sched.h:797 assert_clock_updated()
  rq->clock_update_flags < RQCF_ACT_SKIP

  Call Trace:
    dump_stack()
    __warn()
    warn_slowpath_fmt()
    assert_clock_updated.isra.63.part.64()
    can_migrate_task()
    load_balance()
    pick_next_task_fair()
    __schedule()
    schedule()
    worker_thread()
    kthread()

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

@@ -8070,6 +8070,7 @@ redo:
 
 more_balance:
 		raw_spin_lock_irqsave(&busiest->lock, flags);
+		update_rq_clock(busiest);
 
 		/*
 		 * cur_ld_moved - load moved in current iteration
@@ -8446,6 +8447,7 @@ static int active_load_balance_cpu_stop(void *data)
 		};
 
 		schedstat_inc(sd->alb_count);
+		update_rq_clock(busiest_rq);
 
 		p = detach_one_task(&env);
 		if (p) {