diff options
Diffstat (limited to 'Documentation/kref.txt')
| -rw-r--r-- | Documentation/kref.txt | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/Documentation/kref.txt b/Documentation/kref.txt index f38b59d00c6..130b6e87aa7 100644 --- a/Documentation/kref.txt +++ b/Documentation/kref.txt @@ -141,10 +141,10 @@ The last rule (rule 3) is the nastiest one to handle. Say, for instance, you have a list of items that are each kref-ed, and you wish to get the first one. You can't just pull the first item off the list and kref_get() it. That violates rule 3 because you are not already -holding a valid pointer. You must add locks or semaphores. For -instance: +holding a valid pointer. You must add a mutex (or some other lock). +For instance: -static DECLARE_MUTEX(sem); +static DEFINE_MUTEX(mutex); static LIST_HEAD(q); struct my_data { @@ -155,12 +155,12 @@ struct my_data static struct my_data *get_entry() { struct my_data *entry = NULL; - down(&sem); + mutex_lock(&mutex); if (!list_empty(&q)) { entry = container_of(q.next, struct my_q_entry, link); kref_get(&entry->refcount); } - up(&sem); + mutex_unlock(&mutex); return entry; } @@ -174,9 +174,9 @@ static void release_entry(struct kref *ref) static void put_entry(struct my_data *entry) { - down(&sem); + mutex_lock(&mutex); kref_put(&entry->refcount, release_entry); - up(&sem); + mutex_unlock(&mutex); } The kref_put() return value is useful if you do not want to hold the @@ -191,13 +191,13 @@ static void release_entry(struct kref *ref) static void put_entry(struct my_data *entry) { - down(&sem); + mutex_lock(&mutex); if (kref_put(&entry->refcount, release_entry)) { list_del(&entry->link); - up(&sem); + mutex_unlock(&mutex); kfree(entry); } else - up(&sem); + mutex_unlock(&mutex); } This is really more useful if you have to call other routines as part |