Revert "sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()"

[~andy/linux] / fs / sysfs / file.c

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 28cc1acd5439bf8caeb6d93e8bf68804ad738b1b..1b8b91b67fdb7a4b192b9568ad1d85defdcd863a 100644 (file)
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -453,3 +453,95 @@ void sysfs_remove_bin_file(struct kobject *kobj,
        kernfs_remove_by_name(kobj->sd, attr->attr.name);
 }
 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
+
+struct sysfs_schedule_callback_struct {
+       struct list_head        workq_list;
+       struct kobject          *kobj;
+       void                    (*func)(void *);
+       void                    *data;
+       struct module           *owner;
+       struct work_struct      work;
+};
+
+static struct workqueue_struct *sysfs_workqueue;
+static DEFINE_MUTEX(sysfs_workq_mutex);
+static LIST_HEAD(sysfs_workq);
+static void sysfs_schedule_callback_work(struct work_struct *work)
+{
+       struct sysfs_schedule_callback_struct *ss = container_of(work,
+                       struct sysfs_schedule_callback_struct, work);
+
+       (ss->func)(ss->data);
+       kobject_put(ss->kobj);
+       module_put(ss->owner);
+       mutex_lock(&sysfs_workq_mutex);
+       list_del(&ss->workq_list);
+       mutex_unlock(&sysfs_workq_mutex);
+       kfree(ss);
+}
+
+/**
+ * sysfs_schedule_callback - helper to schedule a callback for a kobject
+ * @kobj: object we're acting for.
+ * @func: callback function to invoke later.
+ * @data: argument to pass to @func.
+ * @owner: module owning the callback code
+ *
+ * sysfs attribute methods must not unregister themselves or their parent
+ * kobject (which would amount to the same thing).  Attempts to do so will
+ * deadlock, since unregistration is mutually exclusive with driver
+ * callbacks.
+ *
+ * Instead methods can call this routine, which will attempt to allocate
+ * and schedule a workqueue request to call back @func with @data as its
+ * argument in the workqueue's process context.  @kobj will be pinned
+ * until @func returns.
+ *
+ * Returns 0 if the request was submitted, -ENOMEM if storage could not
+ * be allocated, -ENODEV if a reference to @owner isn't available,
+ * -EAGAIN if a callback has already been scheduled for @kobj.
+ */
+int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
+               void *data, struct module *owner)
+{
+       struct sysfs_schedule_callback_struct *ss, *tmp;
+
+       if (!try_module_get(owner))
+               return -ENODEV;
+
+       mutex_lock(&sysfs_workq_mutex);
+       list_for_each_entry_safe(ss, tmp, &sysfs_workq, workq_list)
+               if (ss->kobj == kobj) {
+                       module_put(owner);
+                       mutex_unlock(&sysfs_workq_mutex);
+                       return -EAGAIN;
+               }
+       mutex_unlock(&sysfs_workq_mutex);
+
+       if (sysfs_workqueue == NULL) {
+               sysfs_workqueue = create_singlethread_workqueue("sysfsd");
+               if (sysfs_workqueue == NULL) {
+                       module_put(owner);
+                       return -ENOMEM;
+               }
+       }
+
+       ss = kmalloc(sizeof(*ss), GFP_KERNEL);
+       if (!ss) {
+               module_put(owner);
+               return -ENOMEM;
+       }
+       kobject_get(kobj);
+       ss->kobj = kobj;
+       ss->func = func;
+       ss->data = data;
+       ss->owner = owner;
+       INIT_WORK(&ss->work, sysfs_schedule_callback_work);
+       INIT_LIST_HEAD(&ss->workq_list);
+       mutex_lock(&sysfs_workq_mutex);
+       list_add_tail(&ss->workq_list, &sysfs_workq);
+       mutex_unlock(&sysfs_workq_mutex);
+       queue_work(sysfs_workqueue, &ss->work);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_schedule_callback);