Horrible workaround for hanging mount_mfs processes that received a signal.

After finding the third deadlock during dounmount, I decided that it would
be less painful to let the unmounting be handled with a separate thread.
XXX - this is a kludge.

1 files changed, 32 insertions, 11 deletions

diff --git a/sys/ufs/mfs/mfs_vfsops.c b/sys/ufs/mfs/mfs_vfsops.c
index cb01fc418d7..ad415f35cf5 100644
--- a/sys/ufs/mfs/mfs_vfsops.c
+++ b/sys/ufs/mfs/mfs_vfsops.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mfs_vfsops.c,v 1.8 1999/05/31 17:34:55 millert Exp $	*/
+/*	$OpenBSD: mfs_vfsops.c,v 1.9 1999/09/03 18:18:16 art Exp $	*/
 /*	$NetBSD: mfs_vfsops.c,v 1.10 1996/02/09 22:31:28 christos Exp $	*/
 
 /*
@@ -46,6 +46,7 @@
 #include <sys/signalvar.h>
 #include <sys/vnode.h>
 #include <sys/malloc.h>
+#include <sys/kthread.h>
 
 #include <ufs/ufs/quota.h>
 #include <ufs/ufs/inode.h>
@@ -65,6 +66,9 @@ static	int mfs_minor;	/* used for building internal dev_t */
 
 extern int (**mfs_vnodeop_p) __P((void *));
 
+int	mfs_dounmount __P((struct mount *));
+void	mfs_dounmount1 __P((void *));
+
 /*
  * mfs vfs operations.
  */
@@ -272,16 +276,8 @@ mfs_start(mp, flags, p)
 		 * EINTR/ERESTART.
 		 */
 		if (tsleep((caddr_t)vp, mfs_pri, "mfsidl", 0)) {
-			/*
-			 * Don't attempt to unmount when MNT_UNMOUNT is set,
-			 * that means that someone is waiting for us to
-			 * finish our operations and it also means that
-			 * we will sleep until he is finished. deadlock.
-			 * XXX - there is a multiprocessor race here.
-			 */
-			if ((mp->mnt_flag & MNT_UNMOUNT) ||
-			    dounmount(mp, 0, p) != 0)
-				CLRSIG(p, CURSIG(p));
+			mfs_dounmount(mp);
+			CLRSIG(p, CURSIG(p));
 		}
 	}
 	return (0);
@@ -305,3 +301,28 @@ mfs_statfs(mp, sbp, p)
 		    &sbp->mount_info.mfs_args, sizeof(struct mfs_args));
 	return (error);
 }
+
+/*
+ * Spawn off a kernel thread to do the unmounting to avoid all deadlocks.
+ * XXX - this is horrible, but it was the only sane thing to do.
+ */
+int
+mfs_dounmount(mp)
+	struct mount *mp;
+{
+	if (kthread_create(mfs_dounmount1, (void *)mp, NULL, "mfs_unmount"))
+		return 1;
+
+	return 0;
+}
+
+void
+mfs_dounmount1(v)
+	void *v;
+{
+	struct mount *mp = v;
+
+	dounmount(mp, 0, curproc);
+
+	kthread_exit(0);
+}