Multiple updates on sleeping, vma dropping and thread suspend.

- Updated sleeping paths such that a task is atomically put into
  a runqueue and made RUNNABLE, or removed from a runqueue and made SLEEPING.
- Modified vma dropping sources to handle both copy_on_write() and exit() cases
  in a common function.
- Added the first infrastructure to have a pager to suspend a task and wait for
  suspend completion from the scheduler.

include/l4/lib/wait.h

@@ -34,8 +34,40 @@ void task_set_wqh(struct ktcb *task, struct waitqueue_head *wqh,
 void task_unset_wqh(struct ktcb *task);
 
 
+/*
+ * Sleep if the given condition isn't true.
+ * ret will tell whether condition was met
+ * or we got interrupted.
+ */
+#define WAIT_EVENT(wqh, condition, ret)				\
+do {								\
+	ret = 0;						\
+	for (;;) {						\
+		spin_lock(&(wqh)->slock);			\
+		if (condition) {				\
+			spin_unlock(&(wqh)->slock);		\
+			break;					\
+		}						\
+		CREATE_WAITQUEUE_ON_STACK(wq, current);		\
+		task_set_wqh(current, wqh, &wq);		\
+		(wqh)->sleepers++;				\
+		list_add_tail(&wq.task_list, &(wqh)->task_list);\
+		printk("(%d) waiting...\n", current->tid);	\
+		sched_prepare_sleep();				\
+		spin_unlock(&(wqh)->slock);			\
+		schedule();					\
+		/* Did we wake up normally or get interrupted */\
+		if (current->flags & TASK_INTERRUPTED) {	\
+			current->flags &= ~TASK_INTERRUPTED;	\
+			ret = -EINTR;				\
+			break;					\
+		}						\
+	}							\
+} while(0);
+
 void wake_up(struct waitqueue_head *wqh, int sync);
 int wake_up_task(struct ktcb *task, int sync);
+void wake_up_all(struct waitqueue_head *wqh, int sync);
 
 #endif /* __LIB_WAIT_H__ */