Make termination of objects wait for possible collapses before altering

the object's shadow linkage.  Also note that the object is going to die
so that a possible collapse can finish early.

diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 0fa0d2e..722d2f5 100644 (file)
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vm_object.c,v 1.12 1996/11/06 23:24:40 niklas Exp $   */
+/*     $OpenBSD: vm_object.c,v 1.13 1996/12/24 20:14:28 niklas Exp $   */
 /*     $NetBSD: vm_object.c,v 1.34 1996/02/28 22:35:35 gwr Exp $       */
 
 /* 
@@ -337,6 +337,21 @@ vm_object_terminate(object)
        register vm_page_t      p;
        vm_object_t             shadow_object;
 
+       /*
+        * Setters of paging_in_progress might be interested that this object
+        * is going away as soon as we get a grip on it.
+        */
+       object->flags |= OBJ_FADING;
+
+       /*
+        * Wait until the pageout daemon is through with the object or a
+        * potential collapse operation is finished.
+        */
+       while (object->paging_in_progress) {
+               vm_object_sleep(object, object, FALSE);
+               vm_object_lock(object);
+       }
+
        /*
         *      Detach the object from its shadow if we are the shadow's
         *      copy.
@@ -353,14 +368,6 @@ vm_object_terminate(object)
                vm_object_unlock(shadow_object);
        }
 
-       /*
-        * Wait until the pageout daemon is through with the object.
-        */
-       while (object->paging_in_progress) {
-               vm_object_sleep(object, object, FALSE);
-               vm_object_lock(object);
-       }
-
        /*
         * If not an internal object clean all the pages, removing them
         * from paging queues as we go.
@@ -1340,6 +1347,18 @@ vm_object_collapse_aux(object)
                                thread_wakeup(backing_object);
                                thread_wakeup(object);
 
+                               /*
+                                *      During the pagein vm_object_terminate
+                                *      might have slept on our front object in
+                                *      order to remove it.  If this is the
+                                *      case, we might as well stop all the
+                                *      collapse work right here.
+                                */
+                               if (object->flags & OBJ_FADING) {
+                                       PAGE_WAKEUP(backing_page);
+                                       return KERN_FAILURE;
+                               }
+
                                /*
                                 *      Third, relookup in case pager changed
                                 *      page.  Pager is responsible for

diff --git a/sys/vm/vm_object.h b/sys/vm/vm_object.h
index 46a7939..be739e1 100644 (file)
--- a/sys/vm/vm_object.h
+++ b/sys/vm/vm_object.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: vm_object.h,v 1.3 1996/08/02 00:06:02 niklas Exp $    */
+/*     $OpenBSD: vm_object.h,v 1.4 1996/12/24 20:14:32 niklas Exp $    */
 /*     $NetBSD: vm_object.h,v 1.16 1995/03/29 22:10:28 briggs Exp $    */
 
 /* 
@@ -110,6 +110,7 @@ struct vm_object {
 #define OBJ_CANPERSIST 0x0001  /* allow to persist */
 #define OBJ_INTERNAL   0x0002  /* internally created object */
 #define OBJ_ACTIVE     0x0004  /* used to mark active objects */
+#define OBJ_FADING     0x0008  /* tell others that the object is going away */
 
 TAILQ_HEAD(vm_object_hash_head, vm_object_hash_entry);