tick/broadcast: Sanity check the shutdown of the local clock_event

The broadcast code shuts down the local clock event unconditionally
even if no broadcast device is installed or if the broadcast device is
hrtimer based.

Add proper sanity checks.

[ Split out from a larger combo patch ]

Reported-and-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 a762040..9877d0b 100644 (file)
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -159,7 +159,7 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 {
        struct clock_event_device *bc = tick_broadcast_device.evtdev;
        unsigned long flags;
-       int ret;
+       int ret = 0;
 
        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 
@@ -221,13 +221,14 @@ int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
                         * If we kept the cpu in the broadcast mask,
                         * tell the caller to leave the per cpu device
                         * in shutdown state. The periodic interrupt
-                        * is delivered by the broadcast device.
+                        * is delivered by the broadcast device, if
+                        * the broadcast device exists and is not
+                        * hrtimer based.
                         */
-                       ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
+                       if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
+                               ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
                        break;
                default:
-                       /* Nothing to do */
-                       ret = 0;
                        break;
                }
        }
@@ -373,8 +374,16 @@ void tick_broadcast_control(enum tick_broadcast_mode mode)
        case TICK_BROADCAST_ON:
                cpumask_set_cpu(cpu, tick_broadcast_on);
                if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
-                       if (tick_broadcast_device.mode ==
-                           TICKDEV_MODE_PERIODIC)
+                       /*
+                        * Only shutdown the cpu local device, if:
+                        *
+                        * - the broadcast device exists
+                        * - the broadcast device is not a hrtimer based one
+                        * - the broadcast device is in periodic mode to
+                        *   avoid a hickup during switch to oneshot mode
+                        */
+                       if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
+                           tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
                                clockevents_shutdown(dev);
                }
                break;