From owner-freebsd-net@FreeBSD.ORG Thu Dec 13 18:47:34 2007 Return-Path: Delivered-To: net@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2BC0916A512 for ; Thu, 13 Dec 2007 18:47:34 +0000 (UTC) (envelope-from julian@elischer.org) Received: from outF.internet-mail-service.net (outF.internet-mail-service.net [216.240.47.229]) by mx1.freebsd.org (Postfix) with ESMTP id F285713C448 for ; Thu, 13 Dec 2007 18:47:33 +0000 (UTC) (envelope-from julian@elischer.org) Received: from mx0.idiom.com (HELO idiom.com) (216.240.32.160) by out.internet-mail-service.net (qpsmtpd/0.40) with ESMTP; Thu, 13 Dec 2007 10:33:24 -0800 Received: from julian-mac.elischer.org (localhost [127.0.0.1]) by idiom.com (Postfix) with ESMTP id A190E126CAE; Thu, 13 Dec 2007 10:33:23 -0800 (PST) Message-ID: <47617AF5.7070701@elischer.org> Date: Thu, 13 Dec 2007 10:33:25 -0800 From: Julian Elischer User-Agent: Thunderbird 2.0.0.9 (Macintosh/20071031) MIME-Version: 1.0 To: Maxime Henrion References: <20071213133817.GC71713@elvis.mu.org> In-Reply-To: <20071213133817.GC71713@elvis.mu.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: glebius@FreeBSD.org, net@FreeBSD.org Subject: Re: Deadlock in the routing code X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Dec 2007 18:47:34 -0000 Maxime Henrion wrote: > Replying to myself on this one, sorry about that. > > I said in my previous mail that I didn't know yet what process was > holding the lock of the rtentry that the routed process is dealing > with in rt_setgate(), and I just could verify that it is held by > the swi1: net thread. > > So, in a nutshell: > > - The routed process does its business on the routing socket, that ends up > calling rt_setgate(). While in rt_setgate() it drops the lock on its > rtentry in order to call rtalloc1(). At this point, the routed > process hold the gateway route (rtalloc1() returns it locked), and it > now tries to re-lock the original rtentry. > - At the same time, the swi net thread calls arpresolve() which ends up > calling rt_check(). Then rt_check() locks the rtentry, and tries to > lock the gateway route. > > A classical case of deadlock with mutexes because of different locking > order. Now, it's not obvious to me how to fix it :-). On failure to re-lock, the routed call to rt_setgate should completely abort and restart from scratch, releasing all locks it has on the way out. > Maxime > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"