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.
Unified · Split
| @@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh · 172 unmodified lines | ||
| 173 | 173 | extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, |
| 174 | 174 | unsigned long val_up, unsigned long val_down, void *v); |
| 175 | 175 | |
| 176 | +extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); | |
| 177 | + | |
| 176 | 178 | #define NOTIFY_DONE 0x0000 /* Don't care */ |
| 177 | 179 | #define NOTIFY_OK 0x0001 /* Suits me */ |
| 178 | 180 | #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ |
| @@ -204,6 +204,19 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh, · 203 unmodified lines | ||
| 204 | 204 | EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); |
| 205 | 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 | 221 | * Blocking notifier chain routines. All access to the chain is |
| 209 | 222 | * synchronized by an rwsem. |