svn commit: r250807 - user/attilio/vmobj-readlock/sys/vm

[Attilio Rao]

Author: attilio
Date: Sun May 19 14:59:24 2013
New Revision: 250807
URL: http://svnweb.freebsd.org/changeset/base/250807

Log:
  Remove the necessity to define VM_OBJECT_LOCK_DOWNGRADE() and handle
  the race differently.
  
  Sponsored by:	EMC / Isilon storage division

Modified:
  user/attilio/vmobj-readlock/sys/vm/vm_map.c
  user/attilio/vmobj-readlock/sys/vm/vm_object.h

Modified: user/attilio/vmobj-readlock/sys/vm/vm_map.c
==============================================================================
--- user/attilio/vmobj-readlock/sys/vm/vm_map.c	Sun May 19 07:44:01 2013	(r250806)
+++ user/attilio/vmobj-readlock/sys/vm/vm_map.c	Sun May 19 14:59:24 2013	(r250807)
@@ -1806,6 +1806,7 @@ vm_map_pmap_enter(vm_map_t map, vm_offse
 
 	if ((prot & (VM_PROT_READ | VM_PROT_EXECUTE)) == 0 || object == NULL)
 		return;
+relock:
 	VM_OBJECT_RLOCK(object);
 	if (object->type == OBJT_DEVICE || object->type == OBJT_SG) {
 		VM_OBJECT_RUNLOCK(object);
@@ -1816,7 +1817,8 @@ vm_map_pmap_enter(vm_map_t map, vm_offse
 			VM_OBJECT_WUNLOCK(object);
 			return;
 		}
-		VM_OBJECT_LOCK_DOWNGRADE(object);
+		VM_OBJECT_WUNLOCK(object);
+		goto relock;
 	}
 
 	psize = atop(size);

Modified: user/attilio/vmobj-readlock/sys/vm/vm_object.h
==============================================================================
--- user/attilio/vmobj-readlock/sys/vm/vm_object.h	Sun May 19 07:44:01 2013	(r250806)
+++ user/attilio/vmobj-readlock/sys/vm/vm_object.h	Sun May 19 14:59:24 2013	(r250807)
@@ -223,8 +223,6 @@ extern struct vm_object kmem_object_stor
 	rw_assert(&(object)->lock, RA_RLOCKED)
 #define	VM_OBJECT_ASSERT_WLOCKED(object)				\
 	rw_assert(&(object)->lock, RA_WLOCKED)
-#define	VM_OBJECT_LOCK_DOWNGRADE(object)				\
-	rw_downgrade(&(object)->lock)
 #define	VM_OBJECT_RLOCK(object)						\
 	rw_rlock(&(object)->lock)
 #define	VM_OBJECT_RUNLOCK(object)					\