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-rw-r--r--Documentation/kref.txt20
1 files changed, 10 insertions, 10 deletions
diff --git a/Documentation/kref.txt b/Documentation/kref.txt
index f38b59d00c63..130b6e87aa7e 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
141instance, you have a list of items that are each kref-ed, and you wish 141instance, you have a list of items that are each kref-ed, and you wish
142to get the first one. You can't just pull the first item off the list 142to get the first one. You can't just pull the first item off the list
143and kref_get() it. That violates rule 3 because you are not already 143and kref_get() it. That violates rule 3 because you are not already
144holding a valid pointer. You must add locks or semaphores. For 144holding a valid pointer. You must add a mutex (or some other lock).
145instance: 145For instance:
146 146
147static DECLARE_MUTEX(sem); 147static DEFINE_MUTEX(mutex);
148static LIST_HEAD(q); 148static LIST_HEAD(q);
149struct my_data 149struct my_data
150{ 150{
@@ -155,12 +155,12 @@ struct my_data
155static struct my_data *get_entry() 155static struct my_data *get_entry()
156{ 156{
157 struct my_data *entry = NULL; 157 struct my_data *entry = NULL;
158 down(&sem); 158 mutex_lock(&mutex);
159 if (!list_empty(&q)) { 159 if (!list_empty(&q)) {
160 entry = container_of(q.next, struct my_q_entry, link); 160 entry = container_of(q.next, struct my_q_entry, link);
161 kref_get(&entry->refcount); 161 kref_get(&entry->refcount);
162 } 162 }
163 up(&sem); 163 mutex_unlock(&mutex);
164 return entry; 164 return entry;
165} 165}
166 166
@@ -174,9 +174,9 @@ static void release_entry(struct kref *ref)
174 174
175static void put_entry(struct my_data *entry) 175static void put_entry(struct my_data *entry)
176{ 176{
177 down(&sem); 177 mutex_lock(&mutex);
178 kref_put(&entry->refcount, release_entry); 178 kref_put(&entry->refcount, release_entry);
179 up(&sem); 179 mutex_unlock(&mutex);
180} 180}
181 181
182The kref_put() return value is useful if you do not want to hold the 182The 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)
191 191
192static void put_entry(struct my_data *entry) 192static void put_entry(struct my_data *entry)
193{ 193{
194 down(&sem); 194 mutex_lock(&mutex);
195 if (kref_put(&entry->refcount, release_entry)) { 195 if (kref_put(&entry->refcount, release_entry)) {
196 list_del(&entry->link); 196 list_del(&entry->link);
197 up(&sem); 197 mutex_unlock(&mutex);
198 kfree(entry); 198 kfree(entry);
199 } else 199 } else
200 up(&sem); 200 mutex_unlock(&mutex);
201} 201}
202 202
203This is really more useful if you have to call other routines as part 203This is really more useful if you have to call other routines as part