tick/broadcast: Return busy when IPI is pending

Tell the idle code not to go deep if the broadcast IPI is about to
arrive.

[ Split out from a larger combo patch ]

Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Suzuki Poulose <Suzuki.Poulose@arm.com>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1507070929360.3916@nanos

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index da7b40f..70b47bc 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -725,11 +725,15 @@ int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
                         * if the cpu local event is earlier than the
                         * broadcast event. If the current CPU is in
                         * the force mask, then we are going to be
-                        * woken by the IPI right away.
+                        * woken by the IPI right away; we return
+                        * busy, so the CPU does not try to go deep
+                        * idle.
                         */
-                       if (!cpumask_test_cpu(cpu, tick_broadcast_force_mask) &&
-                           dev->next_event.tv64 < bc->next_event.tv64)
+                       if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
+                               ret = -EBUSY;
+                       } else if (dev->next_event.tv64 < bc->next_event.tv64) {
                                tick_broadcast_set_event(bc, cpu, dev->next_event);
+                       }
                }
                /*
                 * If the current CPU owns the hrtimer broadcast