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authorDmitry Osipenko <dmitry.osipenko@collabora.com>2022-05-19 14:02:32 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2022-05-19 19:25:06 +0200
commit13dfd97a341a5cf9d15f415dd469f45e971ef12a (patch)
tree956f0adb0fd184cc3fc9ea45e990f47bfccfa56c /kernel/notifier.c
parent42226c989789d8da4af1de0c31070c96726d990c (diff)
notifier: Add atomic_notifier_call_chain_is_empty()
Add atomic_notifier_call_chain_is_empty() that returns true if given atomic call chain is empty. The first user of this new notifier API function will be the kernel power-off core code that will support power-off call chains. The core code will need to check whether there is a power-off handler registered at all in order to decide whether to halt machine or power it off. Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'kernel/notifier.c')
-rw-r--r--kernel/notifier.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/notifier.c b/kernel/notifier.c
index ba005ebf4730..137b902c985b 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -204,6 +204,19 @@ 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.