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Date:      Wed, 1 Sep 2004 16:56:54 -0700
From:      John-Mark Gurney <gurney_j@resnet.uoregon.edu>
To:        Igor Sysoev <is@rambler-co.ru>
Cc:        freebsd-current@freebsd.org
Subject:   Re: panic caused by EVFILT_SIGNAL detaching in rfork()ed thread
Message-ID:  <20040901235654.GG29902@funkthat.com>
In-Reply-To: <20040901224828.Q97970@is.park.rambler.ru>
References:  <20040901144705.K97970@is.park.rambler.ru> <20040901155304.GD29902@funkthat.com> <20040901173757.GF29902@funkthat.com> <20040901224828.Q97970@is.park.rambler.ru>

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Igor Sysoev wrote this message on Wed, Sep 01, 2004 at 23:07 +0400:
> On Wed, 1 Sep 2004, John-Mark Gurney wrote:
> 
> > > > The problem is some how that the knote is being removed from the list
> > > > (or was never on the list), but not being marked detached...
> > > >
> > > > Hmmm. what are the options you are using for rfork?
> > >
> > > The worker process starts two worker threads created by
> > > rfork(RFPROC|RFTHREAD|RFMEM). Each thread opens kqueue and
> > > adds the EVFILT_SIGNAL event.
> > >
> > > If you like I can send to you the source tarball (I do not distribute
> > > the server right now, because it has not the documentation). The build
> > > process is simple. Then you need to press ^C and you will get the panic.
> >
> > I believe this panic may be possible w/o rfork, but I'm not possitive..
> > It's probably an artifact of the fact that the kq was living longer
> > than the proc that had the signal kevent associated with it, which
> > normally does not happen...
> >
> > Attached is a patch..  And let me know if it fixes your panic...
> 
> The patch fixed the panic (I tested on 5.3-BETA2, GENERIC, SMP, HTT,
> SCHED_ULE). Thank you. Could you make the similar patch for 4.x ?

I'm not familar enough with kqueue in 4.x, so I would just add a similar
if (kn->kn_status & KN_DETACHED)
	return;

to the filt_sigdetach function like the other detach functions...

> And one more, could you rename http://people.freebsd.org/~jmg/kqueue.man.html
> into kqueue_preliminary.man.html and place a modern (or at least from
> 4.1-RELEASE) kqueue man page in kqueue.man.html ? Google shows your
> man page at first position and it confuses people. I saw several times
> when people said that kqueue has the incompatible interface between BSDs
> and even between various FreeBSD verisons referring to this man page.

I've renamed it, but I will send admins an email to try to add a
redirect so that broken links won't plauge the net...

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

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



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