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author | Daniel Walker <dwalker@mvista.com> | 2008-02-06 01:37:58 -0800 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2008-02-06 10:41:09 -0800 |
commit | 1373bed34e30b8632aaf43aa85d72329c83f7077 (patch) | |
tree | b8874ac03a70d53394ca63f0f6e79d807b82d006 /Documentation | |
parent | 13f14b4d8be225cbb11ff2be7c048590a9ccf87b (diff) | |
download | op-kernel-dev-1373bed34e30b8632aaf43aa85d72329c83f7077.zip op-kernel-dev-1373bed34e30b8632aaf43aa85d72329c83f7077.tar.gz |
docs: convert kref semaphore to mutex
Just converting this documentation semaphore reference, since we don't
want to promote semaphore usage.
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Acked-by: Corey Minyard <minyard@acm.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-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 f38b59d..130b6e8 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 |