Module Name: src
Committed By: bouyer
Date: Sat Nov 28 10:10:18 UTC 2009
Modified Files:
src/sys/kern: vfs_subr.c
Log Message:
Previous did cause a deadlock with layered FS: the vrele thread
can sleep on the vnode lock, while vget is sleeping on the
VI_INACTNOW flag (or the vget caller is looping on vget returning failure
because of the VI_INACTNOW flag). With layered FSes, the upper and lower
vnodes share the same lock, so the vget() caller above can be already
holding the vnode lock.
Fix by dropping VI_INACTNOW before sleeping on the vnode lock in
vrelel(), and check the ref count again once we have the lock. If the
vnode has more than one reference, donc VOP_INACTIVE it.
Fix PR kern/42318 and PR kern/42377
patch tested by Hisashi T Fujinaka, Joachim König, Stephen Borrill and
Matthias Scheler.
To generate a diff of this commit:
cvs rdiff -u -r1.391 -r1.392 src/sys/kern/vfs_subr.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/vfs_subr.c
diff -u src/sys/kern/vfs_subr.c:1.391 src/sys/kern/vfs_subr.c:1.392
--- src/sys/kern/vfs_subr.c:1.391 Fri Nov 27 16:43:51 2009
+++ src/sys/kern/vfs_subr.c Sat Nov 28 10:10:17 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_subr.c,v 1.391 2009/11/27 16:43:51 pooka Exp $ */
+/* $NetBSD: vfs_subr.c,v 1.392 2009/11/28 10:10:17 bouyer Exp $ */
/*-
* Copyright (c) 1997, 1998, 2004, 2005, 2007, 2008 The NetBSD Foundation, Inc.
@@ -91,7 +91,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_subr.c,v 1.391 2009/11/27 16:43:51 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_subr.c,v 1.392 2009/11/28 10:10:17 bouyer Exp $");
#include "opt_ddb.h"
#include "opt_compat_netbsd.h"
@@ -1429,14 +1429,30 @@
/* The pagedaemon can't wait around; defer. */
defer = true;
} else if (curlwp == vrele_lwp) {
- /* We have to try harder. */
- vp->v_iflag &= ~VI_INACTREDO;
+ /*
+ * We have to try harder. But we can't sleep
+ * with VI_INACTNOW as vget() may be waiting on it.
+ */
+ vp->v_iflag &= ~(VI_INACTREDO|VI_INACTNOW);
+ cv_broadcast(&vp->v_cv);
error = vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK |
LK_RETRY);
if (error != 0) {
/* XXX */
vpanic(vp, "vrele: unable to lock %p");
}
+ mutex_enter(&vp->v_interlock);
+ /*
+ * if we did get another reference while
+ * sleeping, don't try to inactivate it yet.
+ */
+ if (__predict_false(vtryrele(vp))) {
+ VOP_UNLOCK(vp, 0);
+ mutex_exit(&vp->v_interlock);
+ return;
+ }
+ vp->v_iflag |= VI_INACTNOW;
+ mutex_exit(&vp->v_interlock);
defer = false;
} else if ((vp->v_iflag & VI_LAYER) != 0) {
/*
