VPB_BIT_FLAGMASK
(((x) & ~VPB_BIT_FLAGMASK) >> VPB_SHARERS_SHIFT)
(VPB_BIT_EXCLUSIVE | ((u_int)(uintptr_t)curthread & ~VPB_BIT_FLAGMASK))
(_busy_lock & VPB_BIT_FLAGMASK) | VPB_CURTHREAD_EXCLUSIVE)); \