Improve FMLP queue management.wip-fmlp-dequeue

The next owner of a FMLP-protected resource is dequeued from
the FMLP FIFO queue by unlock() (when the resource is freed by
the previous owner) instead of performing the dequeue by the next
owner immediately after it has been woken up.

This simplifies the code a little bit and also reduces potential
spinlock contention.

1 files changed, 7 insertions, 5 deletions

diff --git a/litmus/locking.c b/litmus/locking.c
index 728b56835cf7..2693f1aca859 100644
--- a/litmus/locking.c
+++ b/litmus/locking.c
@@ -107,16 +107,18 @@ asmlinkage long sys_litmus_unlock(int lock_od)
         return err;
 }
 
-struct task_struct* waitqueue_first(wait_queue_head_t *wq)
+struct task_struct* __waitqueue_remove_first(wait_queue_head_t *wq)
 {
-        wait_queue_t *q;
+        wait_queue_t* q;
+        struct task_struct* t = NULL;
 
         if (waitqueue_active(wq)) {
                 q = list_entry(wq->task_list.next,
                                wait_queue_t, task_list);
-                return (struct task_struct*) q->private;
-        } else
-                return NULL;
+                t = (struct task_struct*) q->private;
+                __remove_wait_queue(wq, q);
+        }
+        return(t);
 }