1 files changed, 48 insertions, 43 deletions

diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c
index 44a259338e33..b0f0d15085db 100644
--- a/kernel/cpu_pm.c
+++ b/kernel/cpu_pm.c
@@ -13,21 +13,38 @@
 #include <linux/spinlock.h>
 #include <linux/syscore_ops.h>
 
-static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
+/*
+ * atomic_notifiers use a spinlock_t, which can block under PREEMPT_RT.
+ * Notifications for cpu_pm will be issued by the idle task itself, which can
+ * never block, IOW it requires using a raw_spinlock_t.
+ */
+static struct {
+	struct raw_notifier_head chain;
+	raw_spinlock_t lock;
+} cpu_pm_notifier = {
+	.chain = RAW_NOTIFIER_INIT(cpu_pm_notifier.chain),
+	.lock  = __RAW_SPIN_LOCK_UNLOCKED(cpu_pm_notifier.lock),
+};
+
+static int cpu_pm_notify(enum cpu_pm_event event)
+{
+	int ret;
 
-static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
+	rcu_read_lock();
+	ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
+	rcu_read_unlock();
+
+	return notifier_to_errno(ret);
+}
+
+static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
 {
+	unsigned long flags;
 	int ret;
 
-	/*
-	 * __atomic_notifier_call_chain has a RCU read critical section, which
-	 * could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
-	 * RCU know this.
-	 */
-	rcu_irq_enter_irqson();
-	ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
-		nr_to_call, nr_calls);
-	rcu_irq_exit_irqson();
+	raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
+	ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL);
+	raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
 
 	return notifier_to_errno(ret);
 }
@@ -39,12 +56,17 @@ static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
  * Add a driver to a list of drivers that are notified about
  * CPU and CPU cluster low power entry and exit.
  *
- * This function may sleep, and has the same return conditions as
- * raw_notifier_chain_register.
+ * This function has the same return conditions as raw_notifier_chain_register.
  */
 int cpu_pm_register_notifier(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_register(&cpu_pm_notifier_chain, nb);
+	unsigned long flags;
+	int ret;
+
+	raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
+	ret = raw_notifier_chain_register(&cpu_pm_notifier.chain, nb);
+	raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
 
@@ -54,12 +76,17 @@ EXPORT_SYMBOL_GPL(cpu_pm_register_notifier);
  *
  * Remove a driver from the CPU PM notifier list.
  *
- * This function may sleep, and has the same return conditions as
- * raw_notifier_chain_unregister.
+ * This function has the same return conditions as raw_notifier_chain_unregister.
  */
 int cpu_pm_unregister_notifier(struct notifier_block *nb)
 {
-	return atomic_notifier_chain_unregister(&cpu_pm_notifier_chain, nb);
+	unsigned long flags;
+	int ret;
+
+	raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
+	ret = raw_notifier_chain_unregister(&cpu_pm_notifier.chain, nb);
+	raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
 
@@ -80,18 +107,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
  */
 int cpu_pm_enter(void)
 {
-	int nr_calls = 0;
-	int ret = 0;
-
-	ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
-	if (ret)
-		/*
-		 * Inform listeners (nr_calls - 1) about failure of CPU PM
-		 * PM entry who are notified earlier to prepare for it.
-		 */
-		cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
-
-	return ret;
+	return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
 }
 EXPORT_SYMBOL_GPL(cpu_pm_enter);
 
@@ -109,7 +125,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter);
  */
 int cpu_pm_exit(void)
 {
-	return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
+	return cpu_pm_notify(CPU_PM_EXIT);
 }
 EXPORT_SYMBOL_GPL(cpu_pm_exit);
 
@@ -131,18 +147,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_exit);
  */
 int cpu_cluster_pm_enter(void)
 {
-	int nr_calls = 0;
-	int ret = 0;
-
-	ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
-	if (ret)
-		/*
-		 * Inform listeners (nr_calls - 1) about failure of CPU cluster
-		 * PM entry who are notified earlier to prepare for it.
-		 */
-		cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
-
-	return ret;
+	return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
 }
 EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
 
@@ -163,7 +168,7 @@ EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
  */
 int cpu_cluster_pm_exit(void)
 {
-	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
+	return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
 }
 EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);