Date: Fri, 19 Feb 1999 02:43:20 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Julian Elischer <julian@whistle.com> Cc: Kirk McKusick <mckusick@McKusick.COM>, Jake <jake@checker.org>, Don Lewis <Don.Lewis@tsc.tdk.com>, current@FreeBSD.ORG Subject: Re: softupdate panic, anyone seen this? (fwd) Message-ID: <199902191043.CAA31641@apollo.backplane.com> References: <Pine.BSF.3.95.990218132053.16922A-100000@current1.whistle.com>
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This may or may not be related. In tracking down the sched_sync()
panic I found two bugs.
First, a couple of places where the worklist was not being protected
at splbio(). I'm not 100% sure that this is a problem but the code
is complex enough that it's just too dangerous not to do it.
Second, a double LIST_REMOVE() was being performed in the case where
VOP_FSYNC() would fail to sync all the dirty pages. This can occur
legally for both NFS and filesystems with SOFTUPDATES set.
I'd appreciate it if someone could verify the double LIST_REMOVE()
bug. vn_syncer_add_to_worklist() already removes the vn from
the list ( assuming the VONWORKLIST v_flag is set, which it should be
in this case ).
-Matt
Matthew Dillon
<dillon@backplane.com>
Index: kern/vfs_subr.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/vfs_subr.c,v
retrieving revision 1.186
diff -u -r1.186 vfs_subr.c
--- vfs_subr.c 1999/02/04 18:25:39 1.186
+++ vfs_subr.c 1999/02/19 10:40:17
@@ -881,10 +881,8 @@
/*
* Add an item to the syncer work queue.
*/
-void
-vn_syncer_add_to_worklist(vp, delay)
- struct vnode *vp;
- int delay;
+static void
+vn_syncer_add_to_worklist(struct vnode *vp, int delay)
{
int s, slot;
@@ -928,7 +926,8 @@
starttime = time_second;
/*
- * Push files whose dirty time has expired.
+ * Push files whose dirty time has expired. Be careful
+ * of interrupt race on slp queue.
*/
s = splbio();
slp = &syncer_workitem_pending[syncer_delayno];
@@ -941,16 +940,20 @@
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
(void) VOP_FSYNC(vp, p->p_ucred, MNT_LAZY, p);
VOP_UNLOCK(vp, 0, p);
+ s = splbio();
if (LIST_FIRST(slp) == vp) {
if (TAILQ_EMPTY(&vp->v_dirtyblkhd) &&
vp->v_type != VBLK)
- panic("sched_sync: fsync failed");
+ panic("sched_sync: fsync failed vp %p type %d tag %d", vp, vp->v_type, vp->v_tag);
/*
* Move ourselves to the back of the sync list.
+ * vn_syncer_*worklist() will remove and re-add
+ * the node.
*/
- LIST_REMOVE(vp, v_synclist);
+ /*LIST_REMOVE(vp, v_synclist);*/
vn_syncer_add_to_worklist(vp, syncdelay);
}
+ splx(s);
}
/*
@@ -2841,6 +2844,8 @@
/*
* The syncer vnode is no longer needed and is being decommissioned.
+ *
+ * Modifications to the worklist must be protected at splbio().
*/
static int
sync_reclaim(ap)
@@ -2849,12 +2854,15 @@
} */ *ap;
{
struct vnode *vp = ap->a_vp;
+ int s;
+ s = splbio();
vp->v_mount->mnt_syncer = NULL;
if (vp->v_flag & VONWORKLST) {
LIST_REMOVE(vp, v_synclist);
vp->v_flag &= ~VONWORKLST;
}
+ splx(s);
return (0);
}
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