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.
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| @@ -204,6 +204,19 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh, · 203 unmodified lines | |||
| 204 | EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); | 204 | EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); |
| 205 | NOKPROBE_SYMBOL(atomic_notifier_call_chain); | 205 | NOKPROBE_SYMBOL(atomic_notifier_call_chain); |
| 206 | 206 | ||
| 207 | /** | ||
| 208 | * atomic_notifier_call_chain_is_empty - Check whether notifier chain is empty | ||
| 209 | * @nh: Pointer to head of the atomic notifier chain | ||
| 210 | * | ||
| 211 | * Checks whether notifier chain is empty. | ||
| 212 | * | ||
| 213 | * Returns true is notifier chain is empty, false otherwise. | ||
| 214 | */ | ||
| 215 | bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) | ||
| 216 | { | ||
| 217 | return !rcu_access_pointer(nh->head); | ||
| 218 | } | ||
| 219 | |||
| 207 | /* | 220 | /* |
| 208 | * Blocking notifier chain routines. All access to the chain is | 221 | * Blocking notifier chain routines. All access to the chain is |
| 209 | * synchronized by an rwsem. | 222 | * synchronized by an rwsem. |