svn commit: r301184 - stable/10/sys/vm

[Konstantin Belousov]

Author: kib
Date: Thu Jun  2 02:39:40 2016
New Revision: 301184
URL: https://svnweb.freebsd.org/changeset/base/301184

Log:
  MFC r300758:
  Prevent parallel object collapses.

Modified:
  stable/10/sys/vm/vm_object.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/vm/vm_object.c
==============================================================================
--- stable/10/sys/vm/vm_object.c	Thu Jun  2 02:36:06 2016	(r301183)
+++ stable/10/sys/vm/vm_object.c	Thu Jun  2 02:39:40 2016	(r301184)
@@ -1721,6 +1721,9 @@ vm_object_collapse(vm_object_t object)
 		 * case.
 		 */
 		if (backing_object->ref_count == 1) {
+			vm_object_pip_add(object, 1);
+			vm_object_pip_add(backing_object, 1);
+
 			/*
 			 * If there is exactly one reference to the backing
 			 * object, we can collapse it into the parent.  
@@ -1792,11 +1795,13 @@ vm_object_collapse(vm_object_t object)
 			KASSERT(backing_object->ref_count == 1, (
 "backing_object %p was somehow re-referenced during collapse!",
 			    backing_object));
+			vm_object_pip_wakeup(backing_object);
 			backing_object->type = OBJT_DEAD;
 			backing_object->ref_count = 0;
 			VM_OBJECT_WUNLOCK(backing_object);
 			vm_object_destroy(backing_object);
 
+			vm_object_pip_wakeup(object);
 			object_collapses++;
 		} else {
 			/*