[PATCH][Fix] cpuidle: Run tick_broadcast_exit() with disabled interrupts

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 335f49196fd6 (sched/idle: Use explicit broadcast oneshot
control function) replaced clockevents_notify() invocations in
cpuidle_idle_call() with direct calls to tick_broadcast_enter()
and tick_broadcast_exit(), but it overlooked the fact that
interrupts were already enabled before calling the latter which
led to functional breakage on systems using idle states with the
CPUIDLE_FLAG_TIMER_STOP flag set.

Fix that by moving the invocations of tick_broadcast_enter()
and tick_broadcast_exit() down into cpuidle_enter_state() where
interrupts are still disabled when tick_broadcast_exit() is
called.  Also ensure that interrupts will be disabled before
running tick_broadcast_exit() even if they have been enabled by
the idle state's ->enter callback.  Trigger a WARN_ON_ONCE() in
that case, as we generally don't want that to happen for states
with CPUIDLE_FLAG_TIMER_STOP set.

Fixes: 335f49196fd6 (sched/idle: Use explicit broadcast oneshot control function)
Reported-and-tested-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Reported-and-tested-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Thanks for the testing and ACKs, here it goes again with all tags and
a changelog.

If anything is missing/incorrect, please let me know ASAP as I'm going to
push this to Linus in a couple of days.

---
 drivers/cpuidle/cpuidle.c |   16 ++++++++++++++++
 kernel/sched/idle.c       |   16 ++--------------
 2 files changed, 18 insertions(+), 14 deletions(-)

Index: linux-pm/kernel/sched/idle.c
===================================================================
--- linux-pm.orig/kernel/sched/idle.c
+++ linux-pm/kernel/sched/idle.c
@@ -81,7 +81,6 @@ static void cpuidle_idle_call(void)
 	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 	int next_state, entered_state;
-	unsigned int broadcast;
 	bool reflect;
 
 	/*
@@ -150,17 +149,6 @@ static void cpuidle_idle_call(void)
 		goto exit_idle;
 	}
 
-	broadcast = drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP;
-
-	/*
-	 * Tell the time framework to switch to a broadcast timer
-	 * because our local timer will be shutdown. If a local timer
-	 * is used from another cpu as a broadcast timer, this call may
-	 * fail if it is not available
-	 */
-	if (broadcast && tick_broadcast_enter())
-		goto use_default;
-
 	/* Take note of the planned idle state. */
 	idle_set_state(this_rq(), &drv->states[next_state]);
 
@@ -174,8 +162,8 @@ static void cpuidle_idle_call(void)
 	/* The cpu is no longer idle or about to enter idle. */
 	idle_set_state(this_rq(), NULL);
 
-	if (broadcast)
-		tick_broadcast_exit();
+	if (entered_state == -EBUSY)
+		goto use_default;
 
 	/*
 	 * Give the governor an opportunity to reflect on the outcome
Index: linux-pm/drivers/cpuidle/cpuidle.c
===================================================================
--- linux-pm.orig/drivers/cpuidle/cpuidle.c
+++ linux-pm/drivers/cpuidle/cpuidle.c
@@ -158,9 +158,18 @@ int cpuidle_enter_state(struct cpuidle_d
 	int entered_state;
 
 	struct cpuidle_state *target_state = &drv->states[index];
+	bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
 	ktime_t time_start, time_end;
 	s64 diff;
 
+	/*
+	 * Tell the time framework to switch to a broadcast timer because our
+	 * local timer will be shut down.  If a local timer is used from another
+	 * CPU as a broadcast timer, this call may fail if it is not available.
+	 */
+	if (broadcast && tick_broadcast_enter())
+		return -EBUSY;
+
 	trace_cpu_idle_rcuidle(index, dev->cpu);
 	time_start = ktime_get();
 
@@ -169,6 +178,13 @@ int cpuidle_enter_state(struct cpuidle_d
 	time_end = ktime_get();
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
 
+	if (broadcast) {
+		if (WARN_ON_ONCE(!irqs_disabled()))
+			local_irq_disable();
+
+		tick_broadcast_exit();
+	}
+
 	if (!cpuidle_state_is_coupled(dev, drv, entered_state))
 		local_irq_enable();