From owner-freebsd-hackers@FreeBSD.ORG Thu Aug 10 15:24:09 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 AD42F16A4DD for ; Thu, 10 Aug 2006 15:24:09 +0000 (UTC) (envelope-from brooks@lor.one-eyed-alien.net) Received: from sccmmhc92.asp.att.net (sccmmhc92.asp.att.net [204.127.203.212]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3A2B943D53 for ; Thu, 10 Aug 2006 15:24:07 +0000 (GMT) (envelope-from brooks@lor.one-eyed-alien.net) Received: from lor.one-eyed-alien.net ([12.207.12.9]) by sccmmhc92.asp.att.net (sccmmhc92) with ESMTP id <20060810152406m92002stjge>; Thu, 10 Aug 2006 15:24:06 +0000 Received: from lor.one-eyed-alien.net (localhost [127.0.0.1]) by lor.one-eyed-alien.net (8.13.6/8.13.6) with ESMTP id k7AFNxFd021365; Thu, 10 Aug 2006 10:24:00 -0500 (CDT) (envelope-from brooks@lor.one-eyed-alien.net) Received: (from brooks@localhost) by lor.one-eyed-alien.net (8.13.6/8.13.6/Submit) id k7AFNxf6021364; Thu, 10 Aug 2006 10:23:59 -0500 (CDT) (envelope-from brooks) Date: Thu, 10 Aug 2006 10:23:59 -0500 From: Brooks Davis To: Divacky Roman Message-ID: <20060810152359.GA21318@lor.one-eyed-alien.net> References: <20060810151616.GA17109@stud.fit.vutbr.cz> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="cNdxnHkX5QqsyA0e" Content-Disposition: inline In-Reply-To: <20060810151616.GA17109@stud.fit.vutbr.cz> User-Agent: Mutt/1.5.11 Cc: hackers@freebsd.org Subject: Re: SoC: help with LISTs and killing procs 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: Thu, 10 Aug 2006 15:24:09 -0000 --cNdxnHkX5QqsyA0e Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Aug 10, 2006 at 05:16:17PM +0200, Divacky Roman wrote: > hi >=20 > I am doing this: >=20 > (pseudocode) > LIST_FOREACH_SAFE(em, &td_em->shared->threads, threads, tmp_em) { >=20 > kill(em, SIGKILL); > } >=20 > kill(SIGKILL) calls exit() which calls my exit_hook() >=20 > my exit_hook() does LIST_REMOVE(em, threads). >=20 > the problem is that this is not synchronous so I am getting a panic by IN= VARIANTS > that "Bad link elm prev->next !=3D elm". This is because I list 1st item = in the list > I call kill on it, then process 2nd list, then scheduler preempts my code= and calls > exit() on the first proc which removes the first entry and bad things hap= pen.=20 >=20 > I see this possible solutions: >=20 > make this synchronous, it can be done by something like: >=20 > .... > kill(em, SIGKILL); > wait_for_proc_to_vanish(); >=20 > pls. tell me what do you think about this solution and if its correct wha= t is the wait_for_proc_to_vanish() >=20 > maybe there's some better solution, pls tell me. It sounds like you need a lock protecting the list. If you held it over the whole loop you could signal all processes before the exit_hook could remove any. -- Brooks --cNdxnHkX5QqsyA0e Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFE20+OXY6L6fI4GtQRArGnAJ9bYoA/FKM2i/nC9ruQOgf0eBqVeACggCp3 LYDzzW882nN0kTqY59TqoqI= =wWhk -----END PGP SIGNATURE----- --cNdxnHkX5QqsyA0e--