From owner-freebsd-current@FreeBSD.ORG Mon Jul 11 13:33:52 2011 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7BF21106564A; Mon, 11 Jul 2011 13:33:52 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.zoral.com.ua (mx0.zoral.com.ua [91.193.166.200]) by mx1.freebsd.org (Postfix) with ESMTP id 012F08FC08; Mon, 11 Jul 2011 13:33:51 +0000 (UTC) Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id p6BDXhNC087374 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 11 Jul 2011 16:33:43 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.4/8.14.4) with ESMTP id p6BDXhcW009843; Mon, 11 Jul 2011 16:33:43 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.4/8.14.4/Submit) id p6BDXhRP009841; Mon, 11 Jul 2011 16:33:43 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 11 Jul 2011 16:33:42 +0300 From: Kostik Belousov To: Petr Salinger Message-ID: <20110711133342.GT43872@deviant.kiev.zoral.com.ua> References: <20110711123332.GS43872@deviant.kiev.zoral.com.ua> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="skzcsJvRJWOW8YcK" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: clamav-milter 0.95.2 at skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-3.3 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00, DNS_FROM_OPENWHOIS autolearn=no version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on skuns.kiev.zoral.com.ua Cc: freebsd-hackers@freebsd.org, Robert Millan , current@freebsd.org Subject: Re: [PATCH] Improve LinuxThreads compatibility in rfork() X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 11 Jul 2011 13:33:52 -0000 --skzcsJvRJWOW8YcK Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 11, 2011 at 03:27:56PM +0200, Petr Salinger wrote: > >>This patch made by Petr Salinger improves compatibility with > >>LinuxThreads in rfork() syscall. The Linux clone() implementation > >>allows specifying the signal sent to parent when child terminates > >>(instead of SIGCHLD). > >> > >>As the threading implementation in Debian GNU/kFreeBSD is > >>LinuxThreads-based, we had to diverge from upstream kFreeBSD ABI and > >>implement this extension. > >> > >>I hope it is acceptable for you to use the same encoding, this way we > >>would archieve ABI compatibility to run Debian GNU/kFreeBSD inside a > >>chroot/jail on top of a FreeBSD system. > >> > >>Thanks for considering > >> > >>-- > >>Robert Millan > > > >>--- a/sys/kern/kern_fork.c > >>+++ b/sys/kern/kern_fork.c > >>@@ -477,7 +477,13 @@ > >> p2->p_sigacts =3D newsigacts; > >> } > >> if (flags & RFLINUXTHPN) > >>- p2->p_sigparent =3D SIGUSR1; > >>+ { > >>+ int sig; > >>+ sig =3D RFTHPNSIGNUM(flags); > >>+ if (sig =3D=3D 0) sig =3D SIGUSR1; > >>+ if (sig =3D=3D SIGCHLD) sig =3D 0; > >>+ p2->p_sigparent =3D sig; > >>+ } > >> else > >> p2->p_sigparent =3D SIGCHLD; > >> > >>--- a/sys/sys/unistd.h > >>+++ b/sys/sys/unistd.h > >>@@ -182,6 +182,10 @@ > >> #define RFHIGHPID (1<<18) /* use a pid higher than 10=20 > >> (idleproc) */ > >> #define RFPPWAIT (1<<31) /* parent sleeps until child exits=20 > >> (vfork) */ > >> #define RFKERNELONLY (RFSTOPPED | RFHIGHPID | RFPPWAIT) > >>+#define RFTHPNSHIFT 24 /* reserve bits 24-30 */ > >>+#define RFTHPNMASK 0x7F /* for compatibility with=20 > >>linuxthreads/clone() */ > >>+ /* allow to specify "clone exit parent=20 > >>notification" signal */ > >>+#define RFTHPNSIGNUM(flags) (((flags) >> RFTHPNSHIFT) & RFTHPNMASK) > >> > >> #endif /* __BSD_VISIBLE */ > >> > >I looked at this patch some time ago already. > > > >Can you, please, describe the reasoning behind the > >>+ if (sig =3D=3D SIGCHLD) sig =3D 0; > >line ? >=20 > The main reason is backward compatibility. > The original FreeBSD code allows only to select between > SIGUSR1 or SIGCHLD signals. >=20 > The our extension changes meaning of RFLINUXTHPN to select signal based o= n=20 > bits 24-30 of passed flags instead of using SIGUSR1 every time. >=20 > When the passed "signal" number is zero, it should behave identically > on plain FreeBSD and in our environment, therefore SIGUSR1 is selected. > The assumption is (have been) that (yet) undefined bits are zero. > That way we are backward compatible with original FreeBSD. >=20 > We still need an alternative way to select "none signal is sent" > after child exit (under linux #0 is used). >=20 > The SIGCHLD can be "selected" (also on original FreeBSD) by not specifyin= g=20 > RFLINUXTHPN, therefore combination of RFLINUXTHPN and passed "signal"=20 > number SIGCHLD is (have been) used for "none signal". >=20 > BTW, the opposite side is in >=20 > http://anonscm.debian.org/viewvc/glibc-bsd/trunk/glibc-ports/kfreebsd/clo= ne.c?view=3Dmarkup I shall state that the sig =3D=3D SIGCHLD case is ugly. Having the separate flag "do not send signal to the parent" would be much less clumsy. What are the requirements for the ABI stability for Debian/kFreeBSD ? Can this be fixed now, or is it too late ? Would you care to update the rfork(2) man page ? Also, it would be ideal to reformat the kern_fork.c change according to our style(9). --skzcsJvRJWOW8YcK Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEARECAAYFAk4a+7YACgkQC3+MBN1Mb4gmgwCfUVmivVjIURnzUngyWGE5P9Mf uEoAn3wVaWVpnufNVnAXpok+rJJWwPzB =dmIw -----END PGP SIGNATURE----- --skzcsJvRJWOW8YcK--