* Use condition variables when waiting for busy pages or busy caches.

* Removed a few instances where the page state was set busy directly after 
  allocating it. This is a no-op, since a page is always busy after 
  allocation.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@21875 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/thread_types.h

@@ -152,6 +152,8 @@ struct thread {
 		int32		flags;
 	} sem;
 
+	struct PrivateConditionVariable *condition_variable;
+
 	struct {
 		sem_id		write_sem;
 		sem_id		read_sem;

headers/private/kernel/vm_types.h

@@ -133,6 +133,16 @@ enum {
 	CACHE_TYPE_NULL
 };
 
+#ifdef __cplusplus
+
+#include <condition_variable.h>
+
+struct vm_dummy_page : vm_page {
+	ConditionVariable<vm_page>	busy_condition;
+};
+
+#endif	// __cplusplus
+
 // vm_cache
 typedef struct vm_cache {
 	mutex				lock;