kern/103127: Kernel panic while using thread features in Squid 2.6

[John-Mark Gurney]

John Baldwin wrote this message on Fri, Sep 22, 2006 at 14:25 -0400:
> On Thursday 21 September 2006 22:37, John-Mark Gurney wrote:
> > John Baldwin wrote this message on Thu, Sep 21, 2006 at 21:52 -0400:
> > > On Wednesday 20 September 2006 17:05, John-Mark Gurney wrote:
> > > > Synopsis: Kernel panic while using thread features in Squid 2.6
> > > > 
> > > > State-Changed-From-To: open->feedback
> > > > State-Changed-By: jmg
> > > > State-Changed-When: Wed Sep 20 21:04:55 UTC 2006
> > > > State-Changed-Why: 
> > > > waiting for people to test the patch of badfo_kqfilter that is attached
> > > > to the bug..
> > > 
> > > Should it possibly return EBADF rather than EINVAL?
> > 
> > If we got this far, we have to have a valid fd, maybe ENXIO?
> 
> badfo_* are used for bad (invalid) file descriptors. :)  All the other badfo_* 
> functions return EBADF (except for poll, since it returns an event mask 
> rather than an errno).

except we did have a valid fd since we did an fget on the
descriptor, and that would fail if it was bad:
        if ((fp = fget_locked(fdp, fd)) == NULL || fp->f_ops == &badfileops) {
                FILEDESC_UNLOCK(fdp);
                return (EBADF);
        }

or can f_ops change in the middle?

>From my reading it looks like it can can during a close, but if the
application is doing a simultanious close and attaching a knote, that's
a race condition, and we techincally still have a valid fd till was
can't fget the fd anymore...  just MO of course...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."