close() of an flock'd file is not atomic

[Bruce Evans]

On Wed, 6 Jun 2012, Konstantin Belousov wrote:

> On Wed, Jun 06, 2012 at 08:17:54AM -0400, John Baldwin wrote:
>>...
>> The vn_open_vnode() patch is at
>> http://www.freebsd.org/~jhb/patches/vn_open_vnode.patch
>>
>> I tested it by doing a buildworld -j 32 in a loop while NFS exporting the
>> /usr/obj tree to another machine that did a continual find | xargs md5 loop
>> over the /usr/obj tree.  This survived overnight.
>
> There is #if 0 left in fhopen() which translates ERESTART into EINTR. Is
> it needed ?
>
> Otherwise it looks fine (but still quite hard to read).

This translation in the old code causes the following bogus behaviour:
- some device drivers try to restart open() after revoke().  They return
   ERESTART for this.  But open never restarts, due to this translation.
   Never restarting may be correct, but EINTR is a bogus errno unless the
   open was actually interrupted by a signal, in which case the driver
   should have returned EINTR.  ENXIO is closest to describing "killed
   by revoke".

What case is the translation supposed to fix?

Bruce