Add blocking_notifier_call_chain_is_empty() that returns true if call
chain is empty.
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
include/linux/notifier.h | 2 ++
kernel/notifier.c | 13 +++++++++++++
2 files changed, 15 insertions(+)
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 87069b8459af..d4717bc0ab85 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh
extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
unsigned long val_up, unsigned long val_down, void *v);
+extern bool blocking_notifier_call_chain_is_empty(struct blocking_notifier_head *nh);
+
#define NOTIFY_DONE 0x0000 /* Don't care */
#define NOTIFY_OK 0x0001 /* Suits me */
#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
diff --git a/kernel/notifier.c b/kernel/notifier.c
index ba005ebf4730..4ed6bda8f127 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -323,6 +323,19 @@ int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
}
EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
+/**
+ * blocking_notifier_call_chain_is_empty - Check whether notifier chain is empty
+ * @nh: Pointer to head of the blocking notifier chain
+ *
+ * Checks whether notifier chain is empty.
+ *
+ * Returns true is notifier chain is empty, false otherwise.
+ */
+bool blocking_notifier_call_chain_is_empty(struct blocking_notifier_head *nh)
+{
+ return !rcu_access_pointer(nh->head);
+}
+
/*
* Raw notifier chain routines. There is no protection;
* the caller must provide it. Use at your own risk!
--
2.35.1
