sched/core: Avoid double calling update_rq_clock() in __balance_push_cpu_stop()

There is a double update_rq_clock() invocation:

  __balance_push_cpu_stop()
    update_rq_clock()
    __migrate_task()
      update_rq_clock()

Sadly select_fallback_rq() also needs update_rq_clock() for
__do_set_cpus_allowed(), it is not possible to remove the update from
__balance_push_cpu_stop(). So remove it from __migrate_task() and
ensure all callers of this function call update_rq_clock() prior to
calling it.

Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20230613082012.49615-3-jiahao.os@bytedance.com

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 442efe5..c7db597 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2546,7 +2546,6 @@ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
        if (!is_cpu_allowed(p, dest_cpu))
                return rq;
 
-       update_rq_clock(rq);
        rq = move_queued_task(rq, rf, p, dest_cpu);
 
        return rq;
@@ -2604,10 +2603,12 @@ static int migration_cpu_stop(void *data)
                                goto out;
                }
 
-               if (task_on_rq_queued(p))
+               if (task_on_rq_queued(p)) {
+                       update_rq_clock(rq);
                        rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
-               else
+               } else {
                        p->wake_cpu = arg->dest_cpu;
+               }
 
                /*
                 * XXX __migrate_task() can fail, at which point we might end