UPSTREAM: sched/core: Add missing update_rq_clock() call in set_user_nice()

Address this rq-clock update bug:

  WARNING: CPU: 30 PID: 195 at ../kernel/sched/sched.h:797 set_next_entity()
  rq->clock_update_flags < RQCF_ACT_SKIP

  Call Trace:
    dump_stack()
    __warn()
    warn_slowpath_fmt()
    set_next_entity()
    ? _raw_spin_lock()
    set_curr_task_fair()
    set_user_nice.part.85()
    set_user_nice()
    create_worker()
    worker_thread()
    kthread()
    ret_from_fork()

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>
(cherry picked from commit 2fb8d36787affe26f3536c3d8ec094995a48037d)
Change-Id: I53ba056e72820c7fadb3f022e4ee3b821c0de17d
Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>
Signed-off-by: Chris Redpath <chris.redpath@arm.com>

Author: Peter Zijlstra

kernel/sched/core.c

@@ -3670,6 +3670,8 @@ void set_user_nice(struct task_struct *p, long nice)
 	 * the task might be in the middle of scheduling on another CPU.
 	 */
 	rq = task_rq_lock(p, &flags);
+	update_rq_clock(rq);
+
 	/*
 	 * The RT priorities are set via sched_setscheduler(), but we still
 	 * allow the 'normal' nice value to be set - but as expected