1 files changed, 96 insertions, 56 deletions

diff --git a/kernel/notifier.c b/kernel/notifier.c
index 1b019cbca594..2f9fe7c30287 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -5,14 +5,9 @@
 #include <linux/notifier.h>
 #include <linux/rcupdate.h>
 #include <linux/vmalloc.h>
-#include <linux/reboot.h>
 
-/*
- *	Notifier list for kernel code which wants to be called
- *	at shutdown. This is used to stop any idling DMA operations
- *	and the like.
- */
-BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
+#define CREATE_TRACE_POINTS
+#include <trace/events/notifier.h>
 
 /*
  *	Notifier chain core routines.  The exported routines below
@@ -20,19 +15,24 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
  */
 
 static int notifier_chain_register(struct notifier_block **nl,
-		struct notifier_block *n)
+				   struct notifier_block *n,
+				   bool unique_priority)
 {
 	while ((*nl) != NULL) {
 		if (unlikely((*nl) == n)) {
-			WARN(1, "double register detected");
-			return 0;
+			WARN(1, "notifier callback %ps already registered",
+			     n->notifier_call);
+			return -EEXIST;
 		}
 		if (n->priority > (*nl)->priority)
 			break;
+		if (n->priority == (*nl)->priority && unique_priority)
+			return -EBUSY;
 		nl = &((*nl)->next);
 	}
 	n->next = *nl;
 	rcu_assign_pointer(*nl, n);
+	trace_notifier_register((void *)n->notifier_call);
 	return 0;
 }
 
@@ -42,6 +42,7 @@ static int notifier_chain_unregister(struct notifier_block **nl,
 	while ((*nl) != NULL) {
 		if ((*nl) == n) {
 			rcu_assign_pointer(*nl, n->next);
+			trace_notifier_unregister((void *)n->notifier_call);
 			return 0;
 		}
 		nl = &((*nl)->next);
@@ -58,7 +59,7 @@ static int notifier_chain_unregister(struct notifier_block **nl,
  *			value of this parameter is -1.
  *	@nr_calls:	Records the number of notifications sent. Don't care
  *			value of this field is NULL.
- *	@returns:	notifier_call_chain returns the value returned by the
+ *	Return:		notifier_call_chain returns the value returned by the
  *			last notifier function called.
  */
 static int notifier_call_chain(struct notifier_block **nl,
@@ -80,6 +81,7 @@ static int notifier_call_chain(struct notifier_block **nl,
 			continue;
 		}
 #endif
+		trace_notifier_run((void *)nb->notifier_call);
 		ret = nb->notifier_call(nb, val, v);
 
 		if (nr_calls)
@@ -101,13 +103,13 @@ NOKPROBE_SYMBOL(notifier_call_chain);
  * @val_up:	Value passed unmodified to the notifier function
  * @val_down:	Value passed unmodified to the notifier function when recovering
  *              from an error on @val_up
- * @v		Pointer passed unmodified to the notifier function
+ * @v:		Pointer passed unmodified to the notifier function
  *
  * NOTE:	It is important the @nl chain doesn't change between the two
  *		invocations of notifier_call_chain() such that we visit the
  *		exact same notifier callbacks; this rules out any RCU usage.
  *
- * Returns:	the return value of the @val_up call.
+ * Return:	the return value of the @val_up call.
  */
 static int notifier_call_chain_robust(struct notifier_block **nl,
 				     unsigned long val_up, unsigned long val_down,
@@ -134,7 +136,7 @@ static int notifier_call_chain_robust(struct notifier_block **nl,
  *
  *	Adds a notifier to an atomic notifier chain.
  *
- *	Currently always returns zero.
+ *	Returns 0 on success, %-EEXIST on error.
  */
 int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
 		struct notifier_block *n)
@@ -143,53 +145,57 @@ int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
 	int ret;
 
 	spin_lock_irqsave(&nh->lock, flags);
-	ret = notifier_chain_register(&nh->head, n);
+	ret = notifier_chain_register(&nh->head, n, false);
 	spin_unlock_irqrestore(&nh->lock, flags);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
 
 /**
- *	atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
+ *	atomic_notifier_chain_register_unique_prio - Add notifier to an atomic notifier chain
  *	@nh: Pointer to head of the atomic notifier chain
- *	@n: Entry to remove from notifier chain
+ *	@n: New entry in notifier chain
  *
- *	Removes a notifier from an atomic notifier chain.
+ *	Adds a notifier to an atomic notifier chain if there is no other
+ *	notifier registered using the same priority.
  *
- *	Returns zero on success or %-ENOENT on failure.
+ *	Returns 0 on success, %-EEXIST or %-EBUSY on error.
  */
-int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
-		struct notifier_block *n)
+int atomic_notifier_chain_register_unique_prio(struct atomic_notifier_head *nh,
+					       struct notifier_block *n)
 {
 	unsigned long flags;
 	int ret;
 
 	spin_lock_irqsave(&nh->lock, flags);
-	ret = notifier_chain_unregister(&nh->head, n);
+	ret = notifier_chain_register(&nh->head, n, true);
 	spin_unlock_irqrestore(&nh->lock, flags);
-	synchronize_rcu();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_register_unique_prio);
 
-int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh,
-		unsigned long val_up, unsigned long val_down, void *v)
+/**
+ *	atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
+ *	@nh: Pointer to head of the atomic notifier chain
+ *	@n: Entry to remove from notifier chain
+ *
+ *	Removes a notifier from an atomic notifier chain.
+ *
+ *	Returns zero on success or %-ENOENT on failure.
+ */
+int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
+		struct notifier_block *n)
 {
 	unsigned long flags;
 	int ret;
 
-	/*
-	 * Musn't use RCU; because then the notifier list can
-	 * change between the up and down traversal.
-	 */
 	spin_lock_irqsave(&nh->lock, flags);
-	ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
+	ret = notifier_chain_unregister(&nh->head, n);
 	spin_unlock_irqrestore(&nh->lock, flags);
-
+	synchronize_rcu();
 	return ret;
 }
-EXPORT_SYMBOL_GPL(atomic_notifier_call_chain_robust);
-NOKPROBE_SYMBOL(atomic_notifier_call_chain_robust);
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
 
 /**
  *	atomic_notifier_call_chain - Call functions in an atomic notifier chain
@@ -222,23 +228,27 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
 EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
 NOKPROBE_SYMBOL(atomic_notifier_call_chain);
 
+/**
+ *	atomic_notifier_call_chain_is_empty - Check whether notifier chain is empty
+ *	@nh: Pointer to head of the atomic notifier chain
+ *
+ *	Checks whether notifier chain is empty.
+ *
+ *	Returns true is notifier chain is empty, false otherwise.
+ */
+bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh)
+{
+	return !rcu_access_pointer(nh->head);
+}
+
 /*
  *	Blocking notifier chain routines.  All access to the chain is
  *	synchronized by an rwsem.
  */
 
-/**
- *	blocking_notifier_chain_register - Add notifier to a blocking notifier chain
- *	@nh: Pointer to head of the blocking notifier chain
- *	@n: New entry in notifier chain
- *
- *	Adds a notifier to a blocking notifier chain.
- *	Must be called in process context.
- *
- *	Currently always returns zero.
- */
-int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
-		struct notifier_block *n)
+static int __blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+					      struct notifier_block *n,
+					      bool unique_priority)
 {
 	int ret;
 
@@ -248,16 +258,49 @@ int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
 	 * such times we must not call down_write().
 	 */
 	if (unlikely(system_state == SYSTEM_BOOTING))
-		return notifier_chain_register(&nh->head, n);
+		return notifier_chain_register(&nh->head, n, unique_priority);
 
 	down_write(&nh->rwsem);
-	ret = notifier_chain_register(&nh->head, n);
+	ret = notifier_chain_register(&nh->head, n, unique_priority);
 	up_write(&nh->rwsem);
 	return ret;
 }
+
+/**
+ *	blocking_notifier_chain_register - Add notifier to a blocking notifier chain
+ *	@nh: Pointer to head of the blocking notifier chain
+ *	@n: New entry in notifier chain
+ *
+ *	Adds a notifier to a blocking notifier chain.
+ *	Must be called in process context.
+ *
+ *	Returns 0 on success, %-EEXIST on error.
+ */
+int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+		struct notifier_block *n)
+{
+	return __blocking_notifier_chain_register(nh, n, false);
+}
 EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
 
 /**
+ *	blocking_notifier_chain_register_unique_prio - Add notifier to a blocking notifier chain
+ *	@nh: Pointer to head of the blocking notifier chain
+ *	@n: New entry in notifier chain
+ *
+ *	Adds a notifier to an blocking notifier chain if there is no other
+ *	notifier registered using the same priority.
+ *
+ *	Returns 0 on success, %-EEXIST or %-EBUSY on error.
+ */
+int blocking_notifier_chain_register_unique_prio(struct blocking_notifier_head *nh,
+						 struct notifier_block *n)
+{
+	return __blocking_notifier_chain_register(nh, n, true);
+}
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_register_unique_prio);
+
+/**
  *	blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
  *	@nh: Pointer to head of the blocking notifier chain
  *	@n: Entry to remove from notifier chain
@@ -354,12 +397,12 @@ EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
  *	Adds a notifier to a raw notifier chain.
  *	All locking must be provided by the caller.
  *
- *	Currently always returns zero.
+ *	Returns 0 on success, %-EEXIST on error.
  */
 int raw_notifier_chain_register(struct raw_notifier_head *nh,
 		struct notifier_block *n)
 {
-	return notifier_chain_register(&nh->head, n);
+	return notifier_chain_register(&nh->head, n, false);
 }
 EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
 
@@ -411,7 +454,6 @@ int raw_notifier_call_chain(struct raw_notifier_head *nh,
 }
 EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
 
-#ifdef CONFIG_SRCU
 /*
  *	SRCU notifier chain routines.    Registration and unregistration
  *	use a mutex, and call_chain is synchronized by SRCU (no locks).
@@ -425,7 +467,7 @@ EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
  *	Adds a notifier to an SRCU notifier chain.
  *	Must be called in process context.
  *
- *	Currently always returns zero.
+ *	Returns 0 on success, %-EEXIST on error.
  */
 int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
 		struct notifier_block *n)
@@ -438,10 +480,10 @@ int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
 	 * such times we must not call mutex_lock().
 	 */
 	if (unlikely(system_state == SYSTEM_BOOTING))
-		return notifier_chain_register(&nh->head, n);
+		return notifier_chain_register(&nh->head, n, false);
 
 	mutex_lock(&nh->mutex);
-	ret = notifier_chain_register(&nh->head, n);
+	ret = notifier_chain_register(&nh->head, n, false);
 	mutex_unlock(&nh->mutex);
 	return ret;
 }
@@ -528,8 +570,6 @@ void srcu_init_notifier_head(struct srcu_notifier_head *nh)
 }
 EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
 
-#endif /* CONFIG_SRCU */
-
 static ATOMIC_NOTIFIER_HEAD(die_chain);
 
 int notrace notify_die(enum die_val val, const char *str,