tick: Do not set device to detached state in tick_shutdown()

tick_shutdown() sets the state of the clockevent device to detached
first and the invokes clockevents_exchange_device(), which in turn
invokes clockevents_switch_state().

But clockevents_switch_state() returns without invoking the device shutdown
callback as the device is already in detached state. As a consequence the
timer device is not shutdown when a CPU goes offline.

tick_shutdown() does this because it was originally invoked on a online CPU
and not on the outgoing CPU. It therefore could not access the clockevent
device of the already offlined CPU and just set the state.

Since commit 3b1596a tick_shutdown() is called on the outgoing CPU, so
the hardware device can be accessed.

Remove the state set before calling clockevents_exchange_device(), so that
the subsequent clockevents_switch_state() handles the state transition and
invokes the shutdown callback of the clockevent device.

[ tglx: Massaged change log ]

Fixes: 3b1596a ("clockevents: Shutdown and unregister current clockevents at CPUHP_AP_TICK_DYING")
Signed-off-by: Bibo Mao <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Frederic Weisbecker <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: bibo-mao

kernel/time/clockevents.c

@@ -633,7 +633,7 @@ void tick_offline_cpu(unsigned int cpu)
 	raw_spin_lock(&clockevents_lock);
 
 	tick_broadcast_offline(cpu);
-	tick_shutdown(cpu);
+	tick_shutdown();
 
 	/*
 	 * Unregister the clock event devices which were

kernel/time/tick-common.c

@@ -411,24 +411,18 @@ int tick_cpu_dying(unsigned int dying_cpu)
 }
 
 /*
- * Shutdown an event device on a given cpu:
+ * Shutdown an event device on the outgoing CPU:
  *
- * This is called on a life CPU, when a CPU is dead. So we cannot
- * access the hardware device itself.
- * We just set the mode and remove it from the lists.
+ * Called by the dying CPU during teardown, with clockevents_lock held
+ * and interrupts disabled.
  */
-void tick_shutdown(unsigned int cpu)
+void tick_shutdown(void)
 {
-	struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 	struct clock_event_device *dev = td->evtdev;
 
 	td->mode = TICKDEV_MODE_PERIODIC;
 	if (dev) {
-		/*
-		 * Prevent that the clock events layer tries to call
-		 * the set mode function!
-		 */
-		clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
 		clockevents_exchange_device(dev, NULL);
 		dev->event_handler = clockevents_handle_noop;
 		td->evtdev = NULL;

kernel/time/tick-internal.h

@@ -26,7 +26,7 @@ extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
 extern void tick_handle_periodic(struct clock_event_device *dev);
 extern void tick_check_new_device(struct clock_event_device *dev);
 extern void tick_offline_cpu(unsigned int cpu);
-extern void tick_shutdown(unsigned int cpu);
+extern void tick_shutdown(void);
 extern void tick_suspend(void);
 extern void tick_resume(void);
 extern bool tick_check_replacement(struct clock_event_device *curdev,