Date: Tue, 18 Apr 2000 10:36:15 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Brian Fundakowski Feldman <green@FreeBSD.org> Cc: Alfred Perlstein <bright@wintelcom.net>, Michael Reifenberger <root@nihil.plaut.de>, current@FreeBSD.org, alc@FreeBSD.org Subject: Anyone able to verify the fix for (was Re: panic: vm_object_shadow: source object has OBJ_ONEMAPPING set.) Message-ID: <200004181736.KAA14683@apollo.backplane.com> References: <Pine.BSF.4.21.0004151755001.17351-100000@green.dyndns.org>
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Has Brian or Michael or anyone been able to verify whether my patch
below fixes the reported vm_object_shadow panics yet? I'd like to get
it committed (or scrapped).
-Matt
Index: vm_map.c
===================================================================
RCS file: /home/ncvs/src/sys/vm/vm_map.c,v
retrieving revision 1.187
diff -u -r1.187 vm_map.c
--- vm_map.c 2000/02/28 04:10:35 1.187
+++ vm_map.c 2000/04/15 18:02:06
@@ -2119,10 +2119,14 @@
}
/*
- * Add the reference before calling vm_object_shadow
- * to insure that a shadow object is created.
+ * Clear OBJ_ONEMAPPING before calling vm_object_shadow
+ * to ensure that a shadow object is created. Add a
+ * reference to cover the new vm_map_entry being
+ * associated with the object.
*/
vm_object_reference(object);
+ vm_object_clear_flag(object, OBJ_ONEMAPPING);
+
if (old_entry->eflags & MAP_ENTRY_NEEDS_COPY) {
vm_object_shadow(&old_entry->object.vm_object,
&old_entry->offset,
@@ -2130,7 +2134,6 @@
old_entry->eflags &= ~MAP_ENTRY_NEEDS_COPY;
object = old_entry->object.vm_object;
}
- vm_object_clear_flag(object, OBJ_ONEMAPPING);
/*
* Clone the entry, referencing the shared object.
Index: vm_object.c
===================================================================
RCS file: /home/ncvs/src/sys/vm/vm_object.c,v
retrieving revision 1.171.2.1
diff -u -r1.171.2.1 vm_object.c
--- vm_object.c 2000/03/17 10:47:35 1.171.2.1
+++ vm_object.c 2000/04/15 18:13:58
@@ -900,7 +900,13 @@
source = *object;
/*
- * Don't create the new object if the old object isn't shared.
+ * If the old object is not shared we may be able to simply use it
+ * as the shadow rather then have to create a new object. Only
+ * objects that we can guarentee this case can be optimized - that is,
+ * only objects with no handles that other processes can get a hold
+ * of which are otherwise unassociated, have only one mapping, and
+ * only one reference count. XXX do we need the reference count check
+ * any more? XXX
*/
if (source != NULL &&
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