rwsem: simplify __rwsem_do_wake

[linux-2.6-block.git] / lib / rwsem.c

diff --git a/lib/rwsem.c b/lib/rwsem.c
index 0d50e46d5b0c9bed7a607452615da6fececbec16..9a675fa9d78eb70ad93944506ae53adb4c6f3e3e 100644 (file)
--- a/lib/rwsem.c
+++ b/lib/rwsem.c
@@ -68,20 +68,17 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
        signed long woken, loop, adjustment;
 
        waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
-       if (waiter->type != RWSEM_WAITING_FOR_WRITE)
-               goto readers_only;
-
-       if (wake_type == RWSEM_WAKE_READ_OWNED)
-               /* Another active reader was observed, so wakeup is not
-                * likely to succeed. Save the atomic op.
-                */
+       if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
+               if (wake_type != RWSEM_WAKE_READ_OWNED)
+                       /* Wake writer at the front of the queue, but do not
+                        * grant it the lock yet as we want other writers
+                        * to be able to steal it.  Readers, on the other hand,
+                        * will block as they will notice the queued writer.
+                        */
+                       wake_up_process(waiter->task);
                goto out;
+       }
 
-       /* Wake up the writing waiter and let the task grab the sem: */
-       wake_up_process(waiter->task);
-       goto out;
-
- readers_only:
        /* If we come here from up_xxxx(), another thread might have reached
         * rwsem_down_failed_common() before we acquired the spinlock and
         * woken up a waiter, making it now active.  We prefer to check for
@@ -125,7 +122,8 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
        rwsem_atomic_add(adjustment, sem);
 
        next = sem->wait_list.next;
-       for (loop = woken; loop > 0; loop--) {
+       loop = woken;
+       do {
                waiter = list_entry(next, struct rwsem_waiter, list);
                next = waiter->list.next;
                tsk = waiter->task;
@@ -133,7 +131,7 @@ __rwsem_do_wake(struct rw_semaphore *sem, int wake_type)
                waiter->task = NULL;
                wake_up_process(tsk);
                put_task_struct(tsk);
-       }
+       } while (--loop);
 
        sem->wait_list.next = next;
        next->prev = &sem->wait_list;