nohz: Use nohz own full kick on 2nd task enqueue

Now that we have a nohz full remote kick based on irq work, lets use
it to notify a CPU that it's exiting single task mode.

This unbloats a bit the scheduler IPI that the nohz code was abusing
for its cool "callable anywhere/anytime" properties.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

2 files changed, 2 insertions, 5 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index feb54965e16f..13f5857a15ba 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1574,9 +1574,7 @@ void scheduler_ipi(void)
          */
         preempt_fold_need_resched();
 
-        if (llist_empty(&this_rq()->wake_list)
-                        && !tick_nohz_full_cpu(smp_processor_id())
-                        && !got_nohz_idle_kick())
+        if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
                 return;
 
         /*
@@ -1593,7 +1591,6 @@ void scheduler_ipi(void)
          * somewhat pessimize the simple resched case.
          */
         irq_enter();
-        tick_nohz_full_check();
         sched_ttwu_pending();
 
         /*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 31cc02ebc54e..599a72aff5ea 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1223,7 +1223,7 @@ static inline void add_nr_running(struct rq *rq, unsigned count)
                 if (tick_nohz_full_cpu(rq->cpu)) {
                         /* Order rq->nr_running write against the IPI */
                         smp_wmb();
-                        smp_send_reschedule(rq->cpu);
+                        tick_nohz_full_kick_cpu(rq->cpu);
                 }
        }
 #endif