+ * rt_mutex_start_proxy_lock() - Start lock acquisition for another task
+ * @lock: the rt_mutex to take
+ * @waiter: the pre-initialized rt_mutex_waiter
+ * @task: the task to prepare
+ * @detect_deadlock: perform deadlock detection (1) or not (0)
+ *
+ * Returns:
+ * 0 - task blocked on lock
+ * 1 - acquired the lock for task, caller should wake it up
+ * <0 - error
+ *
+ * Special API call for FUTEX_REQUEUE_PI support.
+ */
+int rt_mutex_start_proxy_lock(struct rt_mutex *lock,
+ struct rt_mutex_waiter *waiter,
+ struct task_struct *task, int detect_deadlock)
+{
+ int ret;
+
+ raw_spin_lock(&lock->wait_lock);
+
+ mark_rt_mutex_waiters(lock);
+
+ if (!rt_mutex_owner(lock) || try_to_steal_lock(lock, task)) {
+ /* We got the lock for task. */
+ debug_rt_mutex_lock(lock);
+ rt_mutex_set_owner(lock, task, 0);
+ raw_spin_unlock(&lock->wait_lock);
+ rt_mutex_deadlock_account_lock(lock, task);
+ return 1;
+ }
+
+ ret = task_blocks_on_rt_mutex(lock, waiter, task, detect_deadlock);
+
+ if (ret && !waiter->task) {
+ /*
+ * Reset the return value. We might have
+ * returned with -EDEADLK and the owner
+ * released the lock while we were walking the
+ * pi chain. Let the waiter sort it out.
+ */
+ ret = 0;
+ }
+ raw_spin_unlock(&lock->wait_lock);
+
+ debug_rt_mutex_print_deadlock(waiter);
+
+ return ret;
+}
+
+/**