1 files changed, 266 insertions, 61 deletions

diff --git a/kernel/sys.c b/kernel/sys.c
index 38bc73e..c93d37f 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -95,99 +95,304 @@ int cad_pid = 1;
  *	and the like. 
  */
 
-static struct notifier_block *reboot_notifier_list;
-static DEFINE_RWLOCK(notifier_lock);
+static BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
+
+/*
+ *	Notifier chain core routines.  The exported routines below
+ *	are layered on top of these, with appropriate locking added.
+ */
+
+static int notifier_chain_register(struct notifier_block **nl,
+		struct notifier_block *n)
+{
+	while ((*nl) != NULL) {
+		if (n->priority > (*nl)->priority)
+			break;
+		nl = &((*nl)->next);
+	}
+	n->next = *nl;
+	rcu_assign_pointer(*nl, n);
+	return 0;
+}
+
+static int notifier_chain_unregister(struct notifier_block **nl,
+		struct notifier_block *n)
+{
+	while ((*nl) != NULL) {
+		if ((*nl) == n) {
+			rcu_assign_pointer(*nl, n->next);
+			return 0;
+		}
+		nl = &((*nl)->next);
+	}
+	return -ENOENT;
+}
+
+static int __kprobes notifier_call_chain(struct notifier_block **nl,
+		unsigned long val, void *v)
+{
+	int ret = NOTIFY_DONE;
+	struct notifier_block *nb;
+
+	nb = rcu_dereference(*nl);
+	while (nb) {
+		ret = nb->notifier_call(nb, val, v);
+		if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK)
+			break;
+		nb = rcu_dereference(nb->next);
+	}
+	return ret;
+}
+
+/*
+ *	Atomic notifier chain routines.  Registration and unregistration
+ *	use a mutex, and call_chain is synchronized by RCU (no locks).
+ */
 
 /**
- *	notifier_chain_register	- Add notifier to a notifier chain
- *	@list: Pointer to root list pointer
+ *	atomic_notifier_chain_register - Add notifier to an atomic notifier chain
+ *	@nh: Pointer to head of the atomic notifier chain
  *	@n: New entry in notifier chain
  *
- *	Adds a notifier to a notifier chain.
+ *	Adds a notifier to an atomic notifier chain.
  *
  *	Currently always returns zero.
  */
+
+int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
+		struct notifier_block *n)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&nh->lock, flags);
+	ret = notifier_chain_register(&nh->head, n);
+	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
+ *	@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;
+
+	spin_lock_irqsave(&nh->lock, flags);
+	ret = notifier_chain_unregister(&nh->head, n);
+	spin_unlock_irqrestore(&nh->lock, flags);
+	synchronize_rcu();
+	return ret;
+}
+
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
+
+/**
+ *	atomic_notifier_call_chain - Call functions in an atomic notifier chain
+ *	@nh: Pointer to head of the atomic notifier chain
+ *	@val: Value passed unmodified to notifier function
+ *	@v: Pointer passed unmodified to notifier function
+ *
+ *	Calls each function in a notifier chain in turn.  The functions
+ *	run in an atomic context, so they must not block.
+ *	This routine uses RCU to synchronize with changes to the chain.
+ *
+ *	If the return value of the notifier can be and'ed
+ *	with %NOTIFY_STOP_MASK then atomic_notifier_call_chain
+ *	will return immediately, with the return value of
+ *	the notifier function which halted execution.
+ *	Otherwise the return value is the return value
+ *	of the last notifier function called.
+ */
  
-int notifier_chain_register(struct notifier_block **list, struct notifier_block *n)
+int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+		unsigned long val, void *v)
 {
-	write_lock(&notifier_lock);
-	while(*list)
-	{
-		if(n->priority > (*list)->priority)
-			break;
-		list= &((*list)->next);
-	}
-	n->next = *list;
-	*list=n;
-	write_unlock(&notifier_lock);
-	return 0;
+	int ret;
+
+	rcu_read_lock();
+	ret = notifier_call_chain(&nh->head, val, v);
+	rcu_read_unlock();
+	return ret;
 }
 
-EXPORT_SYMBOL(notifier_chain_register);
+EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
+
+/*
+ *	Blocking notifier chain routines.  All access to the chain is
+ *	synchronized by an rwsem.
+ */
 
 /**
- *	notifier_chain_unregister - Remove notifier from a notifier chain
- *	@nl: Pointer to root list pointer
+ *	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
  *
- *	Removes a notifier from a notifier chain.
+ *	Adds a notifier to a blocking notifier chain.
+ *	Must be called in process context.
  *
- *	Returns zero on success, or %-ENOENT on failure.
+ *	Currently always returns zero.
  */
  
-int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n)
+int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+		struct notifier_block *n)
 {
-	write_lock(&notifier_lock);
-	while((*nl)!=NULL)
-	{
-		if((*nl)==n)
-		{
-			*nl=n->next;
-			write_unlock(&notifier_lock);
-			return 0;
-		}
-		nl=&((*nl)->next);
-	}
-	write_unlock(&notifier_lock);
-	return -ENOENT;
+	int ret;
+
+	/*
+	 * This code gets used during boot-up, when task switching is
+	 * not yet working and interrupts must remain disabled.  At
+	 * such times we must not call down_write().
+	 */
+	if (unlikely(system_state == SYSTEM_BOOTING))
+		return notifier_chain_register(&nh->head, n);
+
+	down_write(&nh->rwsem);
+	ret = notifier_chain_register(&nh->head, n);
+	up_write(&nh->rwsem);
+	return ret;
 }
 
-EXPORT_SYMBOL(notifier_chain_unregister);
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
 
 /**
- *	notifier_call_chain - Call functions in a notifier chain
- *	@n: Pointer to root pointer of notifier chain
+ *	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
+ *
+ *	Removes a notifier from a blocking notifier chain.
+ *	Must be called from process context.
+ *
+ *	Returns zero on success or %-ENOENT on failure.
+ */
+int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
+		struct notifier_block *n)
+{
+	int ret;
+
+	/*
+	 * This code gets used during boot-up, when task switching is
+	 * not yet working and interrupts must remain disabled.  At
+	 * such times we must not call down_write().
+	 */
+	if (unlikely(system_state == SYSTEM_BOOTING))
+		return notifier_chain_unregister(&nh->head, n);
+
+	down_write(&nh->rwsem);
+	ret = notifier_chain_unregister(&nh->head, n);
+	up_write(&nh->rwsem);
+	return ret;
+}
+
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
+
+/**
+ *	blocking_notifier_call_chain - Call functions in a blocking notifier chain
+ *	@nh: Pointer to head of the blocking notifier chain
  *	@val: Value passed unmodified to notifier function
  *	@v: Pointer passed unmodified to notifier function
  *
- *	Calls each function in a notifier chain in turn.
+ *	Calls each function in a notifier chain in turn.  The functions
+ *	run in a process context, so they are allowed to block.
  *
- *	If the return value of the notifier can be and'd
- *	with %NOTIFY_STOP_MASK, then notifier_call_chain
+ *	If the return value of the notifier can be and'ed
+ *	with %NOTIFY_STOP_MASK then blocking_notifier_call_chain
  *	will return immediately, with the return value of
  *	the notifier function which halted execution.
- *	Otherwise, the return value is the return value
+ *	Otherwise the return value is the return value
  *	of the last notifier function called.
  */
  
-int __kprobes notifier_call_chain(struct notifier_block **n, unsigned long val, void *v)
+int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+		unsigned long val, void *v)
 {
-	int ret=NOTIFY_DONE;
-	struct notifier_block *nb = *n;
+	int ret;
 
-	while(nb)
-	{
-		ret=nb->notifier_call(nb,val,v);
-		if(ret&NOTIFY_STOP_MASK)
-		{
-			return ret;
-		}
-		nb=nb->next;
-	}
+	down_read(&nh->rwsem);
+	ret = notifier_call_chain(&nh->head, val, v);
+	up_read(&nh->rwsem);
 	return ret;
 }
 
-EXPORT_SYMBOL(notifier_call_chain);
+EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
+
+/*
+ *	Raw notifier chain routines.  There is no protection;
+ *	the caller must provide it.  Use at your own risk!
+ */
+
+/**
+ *	raw_notifier_chain_register - Add notifier to a raw notifier chain
+ *	@nh: Pointer to head of the raw notifier chain
+ *	@n: New entry in notifier chain
+ *
+ *	Adds a notifier to a raw notifier chain.
+ *	All locking must be provided by the caller.
+ *
+ *	Currently always returns zero.
+ */
+
+int raw_notifier_chain_register(struct raw_notifier_head *nh,
+		struct notifier_block *n)
+{
+	return notifier_chain_register(&nh->head, n);
+}
+
+EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
+
+/**
+ *	raw_notifier_chain_unregister - Remove notifier from a raw notifier chain
+ *	@nh: Pointer to head of the raw notifier chain
+ *	@n: Entry to remove from notifier chain
+ *
+ *	Removes a notifier from a raw notifier chain.
+ *	All locking must be provided by the caller.
+ *
+ *	Returns zero on success or %-ENOENT on failure.
+ */
+int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
+		struct notifier_block *n)
+{
+	return notifier_chain_unregister(&nh->head, n);
+}
+
+EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
+
+/**
+ *	raw_notifier_call_chain - Call functions in a raw notifier chain
+ *	@nh: Pointer to head of the raw notifier chain
+ *	@val: Value passed unmodified to notifier function
+ *	@v: Pointer passed unmodified to notifier function
+ *
+ *	Calls each function in a notifier chain in turn.  The functions
+ *	run in an undefined context.
+ *	All locking must be provided by the caller.
+ *
+ *	If the return value of the notifier can be and'ed
+ *	with %NOTIFY_STOP_MASK then raw_notifier_call_chain
+ *	will return immediately, with the return value of
+ *	the notifier function which halted execution.
+ *	Otherwise the return value is the return value
+ *	of the last notifier function called.
+ */
+
+int raw_notifier_call_chain(struct raw_notifier_head *nh,
+		unsigned long val, void *v)
+{
+	return notifier_call_chain(&nh->head, val, v);
+}
+
+EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
 
 /**
  *	register_reboot_notifier - Register function to be called at reboot time
@@ -196,13 +401,13 @@ EXPORT_SYMBOL(notifier_call_chain);
  *	Registers a function with the list of functions
  *	to be called at reboot time.
  *
- *	Currently always returns zero, as notifier_chain_register
+ *	Currently always returns zero, as blocking_notifier_chain_register
  *	always returns zero.
  */
  
 int register_reboot_notifier(struct notifier_block * nb)
 {
-	return notifier_chain_register(&reboot_notifier_list, nb);
+	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
 }
 
 EXPORT_SYMBOL(register_reboot_notifier);
@@ -219,7 +424,7 @@ EXPORT_SYMBOL(register_reboot_notifier);
  
 int unregister_reboot_notifier(struct notifier_block * nb)
 {
-	return notifier_chain_unregister(&reboot_notifier_list, nb);
+	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
 }
 
 EXPORT_SYMBOL(unregister_reboot_notifier);
@@ -380,7 +585,7 @@ EXPORT_SYMBOL_GPL(emergency_restart);
 
 void kernel_restart_prepare(char *cmd)
 {
-	notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
+	blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
 	system_state = SYSTEM_RESTART;
 	device_shutdown();
 }
@@ -430,7 +635,7 @@ EXPORT_SYMBOL_GPL(kernel_kexec);
 
 void kernel_shutdown_prepare(enum system_states state)
 {
-	notifier_call_chain(&reboot_notifier_list,
+	blocking_notifier_call_chain(&reboot_notifier_list,
 		(state == SYSTEM_HALT)?SYS_HALT:SYS_POWER_OFF, NULL);
 	system_state = state;
 	device_shutdown();