nohz: Re-evaluate the tick from the scheduler IPI

The scheduler IPI is used by the scheduler to kick
full dynticks CPUs asynchronously when more than one
task are running or when a new timer list timer is
enqueued. This way the destination CPU can decide
to restart the tick to handle this new situation.

Now let's call that kick in the scheduler IPI.

(Reusing the scheduler IPI rather than implementing
a new IPI was suggested by Peter Zijlstra a while ago)

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 4 insertions, 2 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 69f71335984f..9ad35005f1cb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1398,7 +1398,8 @@ static void sched_ttwu_pending(void)
 
 void scheduler_ipi(void)
 {
-        if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
+        if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick()
+            && !tick_nohz_full_cpu(smp_processor_id()))
                 return;
 
         /*
@@ -1415,6 +1416,7 @@ void scheduler_ipi(void)
          * somewhat pessimize the simple resched case.
          */
         irq_enter();
+        tick_nohz_full_check();
         sched_ttwu_pending();
 
         /*
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 884a9f302a06..4d74a68b2c34 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -151,7 +151,7 @@ bool have_nohz_full_mask;
  * Re-evaluate the need for the tick on the current CPU
  * and restart it if necessary.
  */
-static void tick_nohz_full_check(void)
+void tick_nohz_full_check(void)
 {
         /*
          * STUB for now, will be filled with the full tick stop/restart