Date: Fri, 14 Mar 2008 14:30:10 +0200 From: "Vlad GALU" <dudu@dudu.ro> To: freebsd-hackers@freebsd.org Subject: Re: A (perhaps silly) kqueue question Message-ID: <ad79ad6b0803140530td3376b8v9307628ed147a89d@mail.gmail.com> In-Reply-To: <ad79ad6b0803080009w45fc866euf43ea7e9dbf6b5f5@mail.gmail.com> References: <ad79ad6b0803070847v7464381en958ef73455ed9c89@mail.gmail.com> <20080307223723.X42870@fledge.watson.org> <ad79ad6b0803080009w45fc866euf43ea7e9dbf6b5f5@mail.gmail.com>
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On 3/8/08, Vlad GALU <dudu@dudu.ro> wrote:
> On 3/8/08, Robert Watson <rwatson@freebsd.org> wrote:
> > On Fri, 7 Mar 2008, Vlad GALU wrote:
> >
> >
> > > I see an unusual symptom with one of our in-house applications. The main I/O
> > > loop calls kevent(), which in turn returns two events with EV_EOF error set,
> > > always for the same descriptors (they're both socket descriptors). As the
> > > man page is not pretty clear about it and I don't have my UNP copy at hand,
> > > I would like to ask the list whether the error events are supposed to be
> > > one-shot or not.
> >
> >
> > I wonder if it's returning one event for the read socket buffer, and one event
> > for the write socket buffer, since there are really two event sources for each
> > socket? Not that this is desirable behavior, but it might explain it. If you
> > shutdown() only read, do you get back one EOF kevent and one writable kevent?
>
>
> I'll try that and see. The only issue being the low frequency this
> symptom appears at. I'll get back to the list once I have more info.
Haven't gotten to the point of testing shutdown() behavior, but
here's a truss excerpt of the symptom:
-- cut here --
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
kevent(3,0x0,0,{0x7,EVFILT_WRITE,EV_EOF,54,0x832c,0x800d08080
0x7,EVFILT_READ,EV_EOF,54,0x2a,0x800d08080},1024,0x0) = 2 (0x2)
-- and here --
So two EOF are returrned for descriptor 7, and errno would be
ECONNRESET. The question is now, why isn't it oneshot?
>
>
> >
> > Robert N M Watson
> > Computer Laboratory
> > University of Cambridge
> >
>
>
>
> --
> Mahnahmahnah!
>
--
Mahnahmahnah!
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