svn commit: r195095 - user/kmacy/releng_7_2_fcs/sys/vm
Kip Macy
kmacy at FreeBSD.org
Sat Jun 27 06:37:09 UTC 2009
Author: kmacy
Date: Sat Jun 27 06:37:08 2009
New Revision: 195095
URL: http://svn.freebsd.org/changeset/base/195095
Log:
add note that change is a band-aid
Modified:
user/kmacy/releng_7_2_fcs/sys/vm/vm_pageout.c
Modified: user/kmacy/releng_7_2_fcs/sys/vm/vm_pageout.c
==============================================================================
--- user/kmacy/releng_7_2_fcs/sys/vm/vm_pageout.c Sat Jun 27 06:05:10 2009 (r195094)
+++ user/kmacy/releng_7_2_fcs/sys/vm/vm_pageout.c Sat Jun 27 06:37:08 2009 (r195095)
@@ -1089,6 +1089,15 @@ unlock_and_continue:
next = TAILQ_NEXT(m, pageq);
object = m->object;
+
+ /*
+ * XXX note that the object == NULL check is a band-aid
+ * that narrows the race - but really we need to acquire the
+ * page lock before checking the validity of the object pointer
+ * this in turn requires that we trylock the page before
+ * trylocking the object which in turn complicates error
+ * handling slightly
+ */
if ((object == NULL) || (m->flags & PG_MARKER) != 0) {
m = next;
continue;
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