From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 1EDBA3857819; Mon, 13 Sep 2021 08:25:15 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 1EDBA3857819
From: "nsz at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug dynamic-link/19329] dl-tls.c assert failure at concurrent
 pthread_create and dlopen
Date: Mon, 13 Sep 2021 08:25:14 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: glibc
X-Bugzilla-Component: dynamic-link
X-Bugzilla-Version: 2.22
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: nsz at gcc dot gnu.org
X-Bugzilla-Status: RESOLVED
X-Bugzilla-Resolution: FIXED
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: nszabolcs at gmail dot com
X-Bugzilla-Target-Milestone: 2.34
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-19329-131-r2REGmkNtV@http.sourceware.org/bugzilla/>
In-Reply-To: <bug-19329-131@http.sourceware.org/bugzilla/>
References: <bug-19329-131@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: glibc-bugs@sourceware.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Glibc-bugs mailing list <glibc-bugs.sourceware.org>
List-Unsubscribe: <https://sourceware.org/mailman/options/glibc-bugs>,
 <mailto:glibc-bugs-request@sourceware.org?subject=unsubscribe>
List-Archive: <https://sourceware.org/pipermail/glibc-bugs/>
List-Help: <mailto:glibc-bugs-request@sourceware.org?subject=help>
List-Subscribe: <https://sourceware.org/mailman/listinfo/glibc-bugs>,
 <mailto:glibc-bugs-request@sourceware.org?subject=subscribe>
X-List-Received-Date: Mon, 13 Sep 2021 08:25:16 -0000

https://sourceware.org/bugzilla/show_bug.cgi?id=3D19329

--- Comment #40 from Szabolcs Nagy <nsz at gcc dot gnu.org> ---
(In reply to xujing from comment #39)
> I'm sorry, I misled you. I think there is an ABBA deadlock issue in some
> scenarios.
>=20
> If I have a c++ dynamic library(named libA.so) that contains a global
> object, the global object will call the post-constructor at initialization
> and hold it's own lock(named A_lock) when dlopen loads libA.so. Assume th=
at
> two threads execute the following process=EF=BC=9A
>     Thread1:dlopen(libA.so) =3D> hold dl_load_lock =3D> load libA.so =3D>=
 init
> global=20
>             object from libA.so =3D> wait for hold A_lock
>     Thread2:my own code hold A_lock =3D> pthread_create =3D>
> _dl_allocate_tls_init=20
>             =3D> wait for hold dl_load_lock
> In this case, an ABBA deadlock occurs. Is this a bug?

yes i think this should work (it is a lock ordering
issue between a user and libc internal lock, which
is only possible if user code is run while a libc
lock is held)

note that if you replace pthread_create with dlopen
that deadlocks too. so it's still bug 15686. but it
may be more common than i expected. i think we need
to look at fixing that bug. (fixing the dynamic tls
race of this bug without locks in pthread_create is
very hard, so i don't think we can revert the quoted
patch)

--=20
You are receiving this mail because:
You are on the CC list for the bug.=