Messages in this thread Patch in this message | | | Date | Fri, 21 Dec 2007 00:00:03 -0800 | Subject | [PATCH 3/4] docs: convert kref semaphore to mutex | From | Daniel Walker <> |
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Just converting this documentation semaphore reference, since we don't want to promote semaphore usage.
Signed-off-by: Daniel Walker <dwalker@mvista.com>
--- Documentation/kref.txt | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
Index: linux-2.6.23/Documentation/kref.txt =================================================================== --- linux-2.6.23.orig/Documentation/kref.txt +++ linux-2.6.23/Documentation/kref.txt @@ -141,10 +141,10 @@ The last rule (rule 3) is the nastiest o 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 *r 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 *r 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 --
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