UPSTREAM: sched/core: Add missing update_rq_clock() in post_init_entity_util_avg()

Address this rq-clock update bug:

  WARNING: CPU: 0 PID: 0 at ../kernel/sched/sched.h:797 post_init_entity_util_avg()
  rq->clock_update_flags < RQCF_ACT_SKIP

  Call Trace:
    __warn()
    post_init_entity_util_avg()
    wake_up_new_task()
    _do_fork()
    kernel_thread()
    rest_init()
    start_kernel()

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 4126bad6717336abe5d666440ae15555563ca53f)
Change-Id: Ibe9a73386896377f96483d195e433259218755a5
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

@@ -2466,6 +2466,7 @@ void wake_up_new_task(struct task_struct *p)
 	__set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
 #endif
 	rq = __task_rq_lock(p);
+	update_rq_clock(rq);
 	post_init_entity_util_avg(&p->se);
 
 	walt_mark_task_starting(p);