diff options
Diffstat (limited to 'kernel/notifier.c')
| -rw-r--r-- | kernel/notifier.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/kernel/notifier.c b/kernel/notifier.c index 643360d1bb1..823be11584e 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -31,6 +31,21 @@ static int notifier_chain_register(struct notifier_block **nl, return 0; } +static int notifier_chain_cond_register(struct notifier_block **nl, + struct notifier_block *n) +{ + while ((*nl) != NULL) { + if ((*nl) == n) + return 0; + if (n->priority > (*nl)->priority) + break; + nl = &((*nl)->next); + } + n->next = *nl; + rcu_assign_pointer(*nl, n); + return 0; +} + static int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n) { @@ -205,6 +220,29 @@ int blocking_notifier_chain_register(struct blocking_notifier_head *nh, EXPORT_SYMBOL_GPL(blocking_notifier_chain_register); /** + * blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain + * @nh: Pointer to head of the blocking notifier chain + * @n: New entry in notifier chain + * + * Adds a notifier to a blocking notifier chain, only if not already + * present in the chain. + * Must be called in process context. + * + * Currently always returns zero. + */ +int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh, + struct notifier_block *n) +{ + int ret; + + down_write(&nh->rwsem); + ret = notifier_chain_cond_register(&nh->head, n); + up_write(&nh->rwsem); + return ret; +} +EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register); + +/** * blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain * @nh: Pointer to head of the blocking notifier chain * @n: Entry to remove from notifier chain |