Date: Sat, 28 Nov 2009 00:07:06 +0200
From: Kostik Belousov <kostikbel@gmail.com>
To: Joe Marcus Clarke <marcus@freebsd.org>
Cc: "threads@freebsd.org" <threads@freebsd.org>
Subject: Re: [PATCH] Add missing pthread_condattr_{init, destroy} stubs to libc
Message-ID: <20091127220706.GJ2368@deviant.kiev.zoral.com.ua>
In-Reply-To: <1259358800.1608.46.camel@shumai.marcuscom.com>
References: <1259298918.1608.19.camel@shumai.marcuscom.com> <20091127131242.GA2368@deviant.kiev.zoral.com.ua> <1259349248.1608.36.camel@shumai.marcuscom.com> <4AF1E295-0524-4C39-94CD-9A12D574C64D@vigrid.com> <20091127213046.GI2368@deviant.kiev.zoral.com.ua> <1259358800.1608.46.camel@shumai.marcuscom.com>
next in thread | previous in thread | raw e-mail | index | archive | help
--HcccYpVZDxQ8hzPO
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
On Fri, Nov 27, 2009 at 04:53:20PM -0500, Joe Marcus Clarke wrote:
> On Fri, 2009-11-27 at 23:30 +0200, Kostik Belousov wrote:
> > On Fri, Nov 27, 2009 at 04:19:38PM -0500, Daniel Eischen wrote:
> > >=20
> > > On Nov 27, 2009, at 2:14 PM, Joe Marcus Clarke <marcus@freebsd.org> =
=20
> > > wrote:
> > >=20
> > > >On Fri, 2009-11-27 at 15:12 +0200, Kostik Belousov wrote:
> > > >>On Fri, Nov 27, 2009 at 12:15:18AM -0500, Joe Marcus Clarke wrote:
> > > >>>I would like permission to commit this patch which adds missing
> > > >>>pthread_condattr_{init,destroy} symbols to libc. I think I did the
> > > >>>symbol addition correctly (and it seems to work). Without this, t=
he
> > > >>>weak symbols added in the libpthread-stubs port conflict with =20
> > > >>>those in
> > > >>>libthr, and applications with use these symbols can crash.
> > > >>>
> > > >>>I have temporarily hacked libpthread-stubs to fix this, but I real=
ly
> > > >>>feel these stubs should be added to libc. I've also copied kib as=
=20
> > > >>>he
> > > >>>has been kind enough to review my work in the past. Thanks.
> > > >>>
> > > >>>http://www.marcuscom.com/downloads/stubs.diff
> > > >>
> > > >>It is FBSD_1.2 version that we use for symbols added after HEAD =20
> > > >>become
> > > >>CURRENT-9.
> > > >
> > > >Done.
> > >=20
> > > I don't think the symbols belong in FBSD_1.2. They already exist in =
=20
> > > libthr in a previous namespace. If you use FBSD_1.2, then you =20
> > > probably need to bump them in libthr and libc_r, and add compatible =
=20
> > > symbols (no problem there since there are no differences) for the =20
> > > previous versions.
> > Oh, yes.
> >=20
> > >=20
> > > Still not sure why libc needs all libpthread stubs. Shouldn't be =20
> > > necessary.
> >=20
> > The privately discussed plan for 9.0 is to have libthr merged into
> > libc, and have libpthread and libthr as only filter object against libc
> > providing pthread_* and related symbols.
> >=20
> > This would eliminate the need for pthread stubs and solve the issues
> > with (wrongly built) binaries that do not link to libthr but dlopen()
> > libraries that are linked with it.
>=20
> Yeah, I think that would be a great overall solution. However, in this
> case, the binaries in question ARE linked with -pthread. The problem
> can be easily seen by taking this C program:
>=20
> #include <sys/time.h>
> #include <pthread.h>
> #include <string.h>
>=20
> int
> main(void) {
> pthread_condattr_t attr;
>=20
> pthread_condattr_init (&attr);
> pthread_condattr_setclock (&attr, CLOCK_MONOTONIC);
>=20
> pthread_condattr_destroy (&attr);
>=20
> return 0;
> }
>=20
> And compiling it as:
>=20
> cc -o xxx -L/usr/local/lib -lpthread-stubs -pthread xxx.c
>=20
> You will need devel/libpthread-stubs (version 0.3) installed. When you
> run it, it will segfault. If you then rebuild libc and libthr with my
> stubs.diff patch, then rebuild libpthread-stubs, the problem will go
> away.
I see. What happen there is that both libpthread-stubs and libthr
provide _weak_ symbols pthread_condattr_destroy and pthread_condattr_init.
Actually, these two symbols are the only exported symbols from stubs
library. Due to specified library order, rtld for xxx resolves these
symbols from stubs, not from libthr. But pthread_condattr_setclock
is only exported weak from libthr, and it gets used.
This ends up supplying initialized attributes to pthread_condattr_setclock.
Your patch makes libc provide these two weak symbols, and then
stubs seems to become empty library.
--HcccYpVZDxQ8hzPO
Content-Type: application/pgp-signature
Content-Disposition: inline
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.10 (FreeBSD)
iEYEARECAAYFAksQTYoACgkQC3+MBN1Mb4gMmQCg1kvePXHh5mKeMRJ5vfK5GtRJ
xZ0AnA0BelRxWv83HkObLc05RU47dLSa
=q5am
-----END PGP SIGNATURE-----
--HcccYpVZDxQ8hzPO--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20091127220706.GJ2368>