[src/trunk]: src/sys/kern make list traversing in knote() safe against remova...

[drochner <drochner%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/329d7da6e210
branches:  trunk
changeset: 757662:329d7da6e210
user:      drochner <drochner%NetBSD.org@localhost>
date:      Fri Sep 10 10:23:46 2010 +0000

description:
make list traversing in knote() safe against removal of the entry
while the loop body is executed -- at least in the EVFILT_PROC / exit
case a race condition exists which can cause this
fixes a panic triggered eg by tests/kernel/kqueue/proc1

diffstat:

 sys/kern/kern_event.c |  8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diffs (30 lines):

diff -r 83d1d02ff400 -r 329d7da6e210 sys/kern/kern_event.c
--- a/sys/kern/kern_event.c     Fri Sep 10 10:14:55 2010 +0000
+++ b/sys/kern/kern_event.c     Fri Sep 10 10:23:46 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_event.c,v 1.70 2010/07/01 02:38:30 rmind Exp $    */
+/*     $NetBSD: kern_event.c,v 1.71 2010/09/10 10:23:46 drochner Exp $ */
 
 /*-
  * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_event.c,v 1.70 2010/07/01 02:38:30 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_event.c,v 1.71 2010/09/10 10:23:46 drochner Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1460,9 +1460,9 @@
 void
 knote(struct klist *list, long hint)
 {
-       struct knote *kn;
+       struct knote *kn, *tmpkn;
 
-       SLIST_FOREACH(kn, list, kn_selnext) {
+       SLIST_FOREACH_SAFE(kn, list, kn_selnext, tmpkn) {
                if ((*kn->kn_fop->f_event)(kn, hint))
                        knote_activate(kn);
        }