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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.

Dmitry Osipenko committed 4 years ago

Commit 13dfd971 parent 42226c92 files · +15 −0Browse files

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include/linux/notifier.h+2−0
@@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh · 172 unmodified lines
173173 extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
174174 unsigned long val_up, unsigned long val_down, void *v);
175175
176+extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh);
177+
176178 #define NOTIFY_DONE 0x0000 /* Don't care */
177179 #define NOTIFY_OK 0x0001 /* Suits me */
178180 #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */