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Date:      Wed, 14 Jul 2004 13:35:44 -0400
From:      Brian Fundakowski Feldman <green@FreeBSD.org>
To:        Robert Watson <rwatson@FreeBSD.org>
Cc:        src-committers@FreeBSD.org
Subject:   Re: cvs commit: src/sys/kern kern_event.c src/sys/sys eventvar.h
Message-ID:  <20040714173544.GU1626@green.homeunix.org>
In-Reply-To: <Pine.NEB.3.96L.1040714103934.83353K-100000@fledge.watson.org>
References:  <200407140702.i6E724mV093920@repoman.freebsd.org> <Pine.NEB.3.96L.1040714103934.83353K-100000@fledge.watson.org>

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On Wed, Jul 14, 2004 at 10:43:23AM -0400, Robert Watson wrote:
> 
> On Wed, 14 Jul 2004, Alfred Perlstein wrote:
> 
> >   Log:
> >   Make FIOASYNC, FIOSETOWN and FIOGETOWN work on kqueues.
> 
> Have you tried testing this on a kqueue used to monitor signals?  I'd draw
> your particular attention to the following newly enabled code path:
> 
> pgsigio() -> psignal() -> tdsignal() -> do_tdsignal() -> KNOTE() ->
>   knote() -> KNOTE_ACTIVATE() -> knote_enqueue() -> kqueue_wakeup() ->
>   pgsigio()
> 
> It strikes me that adding sigio support to kqueue opens a massive can of
> worms, not least of which is how you prevent the above from causing the
> system to panic, not to mention how you handle locking in what is
> otherwise a set of leaf functions in kqueue.  I'd like it if you could
> back this out until locking for kqueue is resolved, as while this is no
> doubt a useful feature, having the locking working is much more useful to
> us for 5.3.

Agreed.  Much of kqueue "barely works" as is (that is, other than pretty
much all of it which is broken with regard to concurrency); adding more
interfaces, especially this one, is not a good idea (right now?).

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green@FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\



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