re-order locking to avoid races

SCCS-vsn: sys/miscfs/union/union_vnops.c 8.5

diff --git a/usr/src/sys/miscfs/union/union_vnops.c b/usr/src/sys/miscfs/union/union_vnops.c
index 140352f..be50978 100644 (file)
--- a/usr/src/sys/miscfs/union/union_vnops.c
+++ b/usr/src/sys/miscfs/union/union_vnops.c
@@ -8,7 +8,7 @@
  *
  * %sccs.include.redist.c%
  *
  *
  * %sccs.include.redist.c%
  *

- *     @(#)union_vnops.c       8.4 (Berkeley) %G%
+ *     @(#)union_vnops.c       8.5 (Berkeley) %G%

  */
 
 #include <sys/param.h>
  */
 
 #include <sys/param.h>


@@ -512,7 +512,7 @@ union_access(ap)
        } */ *ap;
 {
        struct union_node *un = VTOUNION(ap->a_vp);
        } */ *ap;
 {
        struct union_node *un = VTOUNION(ap->a_vp);

-       int error = 0;
+       int error = EACCES;

        struct vnode *vp;
 
        if (vp = un->un_lowervp) {
        struct vnode *vp;
 
        if (vp = un->un_lowervp) {


@@ -1153,12 +1153,21 @@ int
 union_lock(ap)
        struct vop_lock_args *ap;
 {
 union_lock(ap)
        struct vop_lock_args *ap;
 {

-       struct union_node *un = VTOUNION(ap->a_vp);
+       struct vnode *vp = ap->a_vp;
+       struct union_node *un;
+
+start:
+       while (vp->v_flag & VXLOCK) {
+               vp->v_flag |= VXWANT;
+               sleep((caddr_t)vp, PINOD);
+       }
+
+       un = VTOUNION(vp);

 
        if (un->un_uppervp) {
                if ((un->un_flags & UN_ULOCK) == 0) {
 
        if (un->un_uppervp) {
                if ((un->un_flags & UN_ULOCK) == 0) {

-                       VOP_LOCK(un->un_uppervp);

                        un->un_flags |= UN_ULOCK;
                        un->un_flags |= UN_ULOCK;

+                       VOP_LOCK(un->un_uppervp);

                }
 #ifdef DIAGNOSTIC
                if (un->un_flags & UN_KLOCK)
                }
 #ifdef DIAGNOSTIC
                if (un->un_flags & UN_KLOCK)


@@ -1166,7 +1175,7 @@ union_lock(ap)
 #endif
        }
 
 #endif
        }
 

-       while (un->un_flags & UN_LOCKED) {
+       if (un->un_flags & UN_LOCKED) {

 #ifdef DIAGNOSTIC
                if (curproc && un->un_pid == curproc->p_pid &&
                            un->un_pid > -1 && curproc->p_pid > -1)
 #ifdef DIAGNOSTIC
                if (curproc && un->un_pid == curproc->p_pid &&
                            un->un_pid > -1 && curproc->p_pid > -1)


@@ -1174,8 +1183,8 @@ union_lock(ap)
 #endif
                un->un_flags |= UN_WANT;
                sleep((caddr_t) &un->un_flags, PINOD);
 #endif
                un->un_flags |= UN_WANT;
                sleep((caddr_t) &un->un_flags, PINOD);

+               goto start;

        }
        }

-       un->un_flags |= UN_LOCKED;

 
 #ifdef DIAGNOSTIC
        if (curproc)
 
 #ifdef DIAGNOSTIC
        if (curproc)


@@ -1184,6 +1193,7 @@ union_lock(ap)
                un->un_pid = -1;
 #endif
 
                un->un_pid = -1;
 #endif
 

+       un->un_flags |= UN_LOCKED;

        return (0);
 }
 
        return (0);
 }