FILE_LOCK() uses a pool mutex, as does the vnode v_vnlock. Since pool

mutexes are supposed to only be used as leaf mutexes, and what appear
to be separate pool mutexes could be aliased together, it is bad idea
for a thread to attempt to hold two pool mutexes at the same time.

Slightly rearrange the code in kern_open() so that FILE_UNLOCK() is
called before calling VOP_GETVOBJECT(), which will grab the v_vnlock
mutex.

1 files changed, 5 insertions, 5 deletions

diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index 6d42736..46ff3aa 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -745,17 +745,17 @@ kern_open(struct thread *td, char *path, enum uio_seg pathseg, int flags,
 		td->td_retval[0] = indx;
 		return 0;
 	}
-
-	/* assert that vn_open created a backing object if one is needed */
-	KASSERT(!vn_canvmio(vp) || VOP_GETVOBJECT(vp, NULL) == 0,
-		("open: vmio vnode has no backing object after vn_open"));
-
 	fp->f_data = vp;
 	fp->f_flag = flags & FMASK;
 	fp->f_ops = &vnops;
 	fp->f_type = (vp->v_type == VFIFO ? DTYPE_FIFO : DTYPE_VNODE);
 	FILEDESC_UNLOCK(fdp);
 	FILE_UNLOCK(fp);
+
+	/* assert that vn_open created a backing object if one is needed */
+	KASSERT(!vn_canvmio(vp) || VOP_GETVOBJECT(vp, NULL) == 0,
+		("open: vmio vnode has no backing object after vn_open"));
+
 	VOP_UNLOCK(vp, 0, td);
 	if (flags & (O_EXLOCK | O_SHLOCK)) {
 		lf.l_whence = SEEK_SET;