Add variant of atomic/blocking_notifier_chain_register() functions that
doesn't allow to register notifier using a duplicated priority. The -EBUSY
error code is returned in this case by the new API functions.
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
include/linux/notifier.h | 5 +++
kernel/notifier.c | 87 +++++++++++++++++++++++++++++++---------
2 files changed, 73 insertions(+), 19 deletions(-)
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index d4717bc0ab85..ccce26197dd2 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -150,6 +150,11 @@ extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
struct notifier_block *nb);
+extern int atomic_notifier_chain_register_unique_prio(
+ struct atomic_notifier_head *nh, struct notifier_block *nb);
+extern int blocking_notifier_chain_register_unique_prio(
+ struct blocking_notifier_head *nh, struct notifier_block *nb);
+
extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
struct notifier_block *nb);
extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
diff --git a/kernel/notifier.c b/kernel/notifier.c
index e30d24ee88e9..77e5112ff05b 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -20,7 +20,7 @@ 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)) {
@@ -29,6 +29,8 @@ static int notifier_chain_register(struct notifier_block **nl,
}
if (n->priority > (*nl)->priority)
break;
+ if (n->priority == (*nl)->priority && unique_priority)
+ return -EBUSY;
nl = &((*nl)->next);
}
n->next = *nl;
@@ -143,12 +145,35 @@ 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_register_unique_prio - 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 an atomic notifier chain if there is no other
+ * notifier registered using the same priority.
+ *
+ * Returns zero on success, -EBUSY otherwise.
+ */
+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_register(&nh->head, n, true);
+ spin_unlock_irqrestore(&nh->lock, flags);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_register_unique_prio);
+
/**
* atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
* @nh: Pointer to head of the atomic notifier chain
@@ -208,18 +233,9 @@ NOKPROBE_SYMBOL(atomic_notifier_call_chain);
* 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;
@@ -229,15 +245,48 @@ 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.
+ *
+ * Currently always returns zero.
+ */
+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 zero on success, -EBUSY otherwise.
+ */
+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
@@ -353,7 +402,7 @@ bool blocking_notifier_call_chain_is_empty(struct blocking_notifier_head *nh)
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);
@@ -432,10 +481,10 @@ 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;
}
--
2.33.1
