sched/idle: Simplify wake_up_idle_cpu()

Now that rq->idle's polling bit is a reliable indication that the cpu is
polling, use it.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: nicolas.pitre@linaro.org
Cc: daniel.lezcano@linaro.org
Cc: umgwanakikbuti@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/922f00761445a830ebb23d058e2ae53956ce2d73.1401902905.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e4c0ddd..6afbfee 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -628,26 +628,7 @@ static void wake_up_idle_cpu(int cpu)
        if (cpu == smp_processor_id())
                return;
 
-       /*
-        * This is safe, as this function is called with the timer
-        * wheel base lock of (cpu) held. When the CPU is on the way
-        * to idle and has not yet set rq->curr to idle then it will
-        * be serialized on the timer wheel base lock and take the new
-        * timer into account automatically.
-        */
-       if (rq->curr != rq->idle)
-               return;
-
-       /*
-        * We can set TIF_RESCHED on the idle task of the other CPU
-        * lockless. The worst case is that the other CPU runs the
-        * idle task through an additional NOOP schedule()
-        */
-       set_tsk_need_resched(rq->idle);
-
-       /* NEED_RESCHED must be visible before we test polling */
-       smp_mb();
-       if (!tsk_is_polling(rq->idle))
+       if (set_nr_and_not_polling(rq->idle))
                smp_send_reschedule(cpu);
        else
                trace_sched_wake_idle_without_ipi(cpu);