Date: Tue, 10 Jul 2012 17:27:46 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Volodymyr Kostyrko <c.kworr@gmail.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, freebsd-standards@freebsd.org Subject: Re: kern/149857: [kqueue] kqueue not reporting EOF under certain circumstances Message-ID: <20120710142746.GD2338@deviant.kiev.zoral.com.ua> In-Reply-To: <4FFC39D9.6080809@gmail.com> References: <4FFC1D2D.4020405@gmail.com> <20120710140203.GA2338@deviant.kiev.zoral.com.ua> <4FFC39D9.6080809@gmail.com>
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On Tue, Jul 10, 2012 at 05:19:05PM +0300, Volodymyr Kostyrko wrote:
> Konstantin Belousov wrote:
> >>This PR is rather old. I just had submitted new test case, now in plain=
c.
> >>
> >>It doesn't work exactly like python version, but the result is the same:
> >>
> >>>clang test.c
> >>>cat test.c | ./a.out
> >>-1 916 0 0 0
> >>-1 0 32768 0 0
> >>>./a.out< test.c
> >>-1 916 0 0 0
> >><- and here we have a complete hang in [kqread].
> >
> >And what is your expectation ?
> >
> >The vnode filter never returns EOF when current file position at the end
> >of file. It is documented that read filter returns when file offset if n=
ot
> >at the end of file, thats all. In fact, EV_EOF is returned on forced=20
> >unmount.
> >I do not see a bug in kqueue.
> >
> >On the other hand, your C code has at least two things that I cannot
> >understand. First, EV_EOF is output flag, it makes absolutely no sense
> >to set it in command.Second, it is mistery for me what do you check with
> > if (kev.flags>> 15 =3D=3D 1) {
> >test.
>=20
> EV_EOF on line 19 actually slipped by my fault, original source omits=20
> that one. It doesn't change anything.
Yes.
>=20
> EV_EOF =3D 1 << 15 =3D 32768. And it _is_ returned when file is feed with=
=20
> the pipe.
>=20
> So you mean this is just my false assumption that EOF _should_ occur on=
=20
> stdin? And it actually occurs only if source is a process which can send=
=20
> EOF?
'Source' cannot be a process. Read filter on pipes can return EV_EOF.
Read filter on vnodes (read: regular files) does not return EV_EOF,
except in situation that is created by manual intervention of
administrator.
It should have been clear from my previous response.
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