From owner-freebsd-hackers@FreeBSD.ORG Wed Mar 22 17:43:23 2006 Return-Path: X-Original-To: hackers@freebsd.org Delivered-To: freebsd-hackers@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5DDB716A401; Wed, 22 Mar 2006 17:43:23 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from fw.zoral.com.ua (ll-227.216.82.212.sovam.net.ua [212.82.216.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0F31443D79; Wed, 22 Mar 2006 17:43:20 +0000 (GMT) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by fw.zoral.com.ua (8.13.3/8.13.3) with ESMTP id k2MHhEZQ008931 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 22 Mar 2006 19:43:14 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.13.4/8.13.4) with ESMTP id k2MHhE6T095775; Wed, 22 Mar 2006 19:43:14 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.13.4/8.13.4/Submit) id k2MHhCRO095774; Wed, 22 Mar 2006 19:43:12 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Wed, 22 Mar 2006 19:43:12 +0200 From: Kostik Belousov To: Kazuaki Oda Message-ID: <20060322174312.GB27116@deviant.kiev.zoral.com.ua> References: <44215FE9.2070602@highway.ne.jp> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="liOOAslEiF7prFVr" Content-Disposition: inline In-Reply-To: <44215FE9.2070602@highway.ne.jp> User-Agent: Mutt/1.4.2.1i X-Virus-Scanned: ClamAV version 0.88, clamav-milter version 0.87 on fw.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-1.4 required=5.0 tests=ALL_TRUSTED autolearn=failed version=3.1.0 X-Spam-Checker-Version: SpamAssassin 3.1.0 (2005-09-13) on fw.zoral.com.ua Cc: kan@freebsd.org, hackers@freebsd.org Subject: Re: dlopen() and dlclose() are not MT-safe? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 22 Mar 2006 17:43:23 -0000 --liOOAslEiF7prFVr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Mar 22, 2006 at 11:32:09PM +0900, Kazuaki Oda wrote: > Hello, >=20 > I compiled the following code on 6.1-PRERELEASE and ran: >=20 > dltest.c > ---------------------------------------------------------------------- > #include > #include > #include > #include > #include > #include >=20 > #define NTHREADS 10 >=20 > void *func(void *dummy); >=20 > int main(void) > { > pthread_t tids[NTHREADS]; > int error; > int i; >=20 > for (i =3D 0; i < NTHREADS; i++) { > error =3D pthread_create(&tids[i], NULL, func, NULL); > if (error) > errc(1, error, "pthread_create"); > } >=20 > for (;;) > sleep(1); >=20 > /* NOTREACHED */ >=20 > exit(0); > } >=20 > void *func(void *dummy) > { > void *h; >=20 > for (;;) { > if ((h =3D dlopen("/usr/lib/libm.so", RTLD_NOW)) =3D=3D NULL) > errx(1, "dlopen: %s", dlerror()); > if (dlclose(h) =3D=3D -1) > errx(1, "dlclose: %s", dlerror()); > } >=20 > /* NOTREACHED */ >=20 > return (NULL); > } > ---------------------------------------------------------------------- >=20 > % cc -Wall -o dltest dltest.c -lpthread > % ./dltest > ld-elf.so.1: assert failed: /usr/src/libexec/rtld-elf/rtld.c:2445 > Segmentation fault (core dumped) >=20 > % cc -Wall -o dltest dltest.c -lthr > % ./dltest > % ld-elf.so.1: assert failed: /usr/src/libexec/rtld-elf/rtld.c:1723 > Abort (core dumped) >=20 > Hmm, it seems dlopen() and dlclose() are not MT-safe. Is this a known > issue? >=20 > -- > Kazuaki Oda The following patch put some relief for the problem: Index: libexec/rtld-elf/rtld.c = =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D RCS file: /usr/local/arch/ncvs/src/libexec/rtld-elf/rtld.c,v retrieving revision 1.112 diff -u -r1.112 rtld.c --- libexec/rtld-elf/rtld.c 24 Dec 2005 15:37:30 -0000 1.112 +++ libexec/rtld-elf/rtld.c 22 Mar 2006 17:33:06 -0000 @@ -1688,6 +1688,12 @@ wlock_release(rtld_bind_lock, lockstate); objlist_call_fini(&list_fini); lockstate =3D wlock_acquire(rtld_bind_lock); + if (root->refcount =3D=3D 0) { + _rtld_error("%s: object busy", root->path); + wlock_release(rtld_bind_lock, lockstate); + return -1; + } + objlist_remove_unref(&list_fini); /* Finish cleaning up the newly-unreferenced objects. */ But it still allows for the mess of _init/_fini simultaneous calls from different threads. SUSv3 does not mention constructors/destructors. --liOOAslEiF7prFVr Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (FreeBSD) iD8DBQFEIYyvC3+MBN1Mb4gRAqNnAJ99oSXZJu2GX6ffvlah05dtDTGqOQCg0cBw V7O5wKkm4D4gjW2NIY/R1ag= =rlPa -----END PGP SIGNATURE----- --liOOAslEiF7prFVr--