Possible kqueue related issue on STABLE/RC.

[Patrick Lamaiziere]

Le Wed, 25 Sep 2013 00:21:27 +0300,
Konstantin Belousov <kostikbel at gmail.com> a écrit :

Hello,

> On Tue, Sep 24, 2013 at 10:45:17AM -0700, John-Mark Gurney wrote:
> > I'd like to understand why you think protecting these functions w/
> > the _DETACHED check is correct...  In kern_event.c, all calls to
> > f_detach are followed by knote_drop which will ensure that the knote
> > is removed and free, so no more f_event calls will be called on that
> > knote..
> 
> My current belief is that what happens is a glitch in the
> kqueue_register(). After a new knote is created and attached, the kq
> lock is dropped and then f_event() is called. If the vnode is
> reclaimed or possible freed meantime, f_event() seems to dereference
> freed memory, since kn_hook points to freed vnode.
> 
> The issue as I see it is that vnode lifecycle is detached from the
> knote lifecycle.  Might be, only the second patch, which acquires a
> hold reference on the vnode for each knote, is really needed.  But
> before going into any conclusions, I want to see the testing results.

Testing looks good with your latest patch. I was able to run a complete
poudriere bulk (870 packages). I'm running another bulk to see.

If you have other patches to test just ask, I have not updated my
packages because there was a change to make gvfsd to ignore some
poudriere activity. So I guess it will be harder to see this
problem.

Many thanks Konstantin,
Regards