Author: kib
Date: Sun Sep 8 17:51:22 2013
New Revision: 255396
URL: http://svnweb.freebsd.org/changeset/base/255396
Log:
Drain for the xbusy state for two places which potentially do
pmap_remove_all(). Not doing the drain allows the pmap_enter() to
proceed in parallel, making the pmap_remove_all() effects void.
The race results in an invalidated page mapped wired by usermode.
Reported and tested by: pho
Reviewed by: alc
Sponsored by: The FreeBSD Foundation
Approved by: re (glebius)
Modified:
head/sys/kern/vfs_bio.c
head/sys/vm/vm_object.c
Modified: head/sys/kern/vfs_bio.c
==============================================================================
--- head/sys/kern/vfs_bio.c Sun Sep 8 17:47:14 2013 (r255395)
+++ head/sys/kern/vfs_bio.c Sun Sep 8 17:51:22 2013 (r255396)
@@ -1693,6 +1693,12 @@ brelse(struct buf *bp)
KASSERT(presid >= 0, ("brelse: extra page"));
VM_OBJECT_WLOCK(obj);
+ while (vm_page_xbusied(m)) {
+ vm_page_lock(m);
+ VM_OBJECT_WUNLOCK(obj);
+ vm_page_busy_sleep(m, "mbncsh");
+ VM_OBJECT_WLOCK(obj);
+ }
if (pmap_page_wired_mappings(m) == 0)
vm_page_set_invalid(m, poffset, presid);
VM_OBJECT_WUNLOCK(obj);
Modified: head/sys/vm/vm_object.c
==============================================================================
--- head/sys/vm/vm_object.c Sun Sep 8 17:47:14 2013 (r255395)
+++ head/sys/vm/vm_object.c Sun Sep 8 17:51:22 2013 (r255396)
@@ -1910,6 +1910,12 @@ again:
* not specified.
*/
vm_page_lock(p);
+ if (vm_page_xbusied(p)) {
+ VM_OBJECT_WUNLOCK(object);
+ vm_page_busy_sleep(p, "vmopax");
+ VM_OBJECT_WLOCK(object);
+ goto again;
+ }
if ((wirings = p->wire_count) != 0 &&
(wirings = pmap_page_wired_mappings(p)) != p->wire_count) {
if ((options & (OBJPR_NOTWIRED | OBJPR_NOTMAPPED)) ==
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