From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [PATCH] sctp: lock_sock_nested in sctp_sock_migrate Date: Mon, 25 Jun 2007 16:24:23 -0400 Message-ID: <46802477.5030005@hp.com> References: <20070622221446.GB7547@mami.zabbo.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: lksctp-developers@lists.sourceforge.net, netdev@vger.kernel.org, Arjan van de Ven To: Zach Brown Return-path: Received: from atlrel6.hp.com ([156.153.255.205]:39939 "EHLO atlrel6.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751334AbXFYUY0 (ORCPT ); Mon, 25 Jun 2007 16:24:26 -0400 In-Reply-To: <20070622221446.GB7547@mami.zabbo.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Zach Brown wrote: > I'm not sure that I've gotten either the sctp or lockdep details right, > but with this patch I don't get lockdep yelling at me any more :) > > ------ > > sctp: lock_sock_nested in sctp_sock_migrate > > sctp_sock_migrate() grabs the socket lock on a newly allocated socket while > holding the socket lock on an old socket. lockdep worries that this might > be a recursive lock attempt. > > task/3026 is trying to acquire lock: > (sk_lock-AF_INET){--..}, at: [] sctp_sock_migrate+0x2e3/0x327 [sctp] > but task is already holding lock: > (sk_lock-AF_INET){--..}, at: [] sctp_accept+0xdf/0x1e3 [sctp] > > This patch tells lockdep that this locking is safe by using > lock_sock_nested(). Hm... This is another case of of two different sockets taking the same lock... Arjan, did this every get fixed, or is the nested locking the right solution to this? Thanks -vlad > > Signed-off-by: Zach Brown > > diff -r 8adcfdf2545b net/sctp/socket.c > --- a/net/sctp/socket.c Fri Jun 22 11:11:33 2007 -0700 > +++ b/net/sctp/socket.c Fri Jun 22 15:05:22 2007 -0700 > @@ -6084,8 +6084,11 @@ static void sctp_sock_migrate(struct soc > * queued to the backlog. This prevents a potential race between > * backlog processing on the old socket and new-packet processing > * on the new socket. > - */ > - sctp_lock_sock(newsk); > + * > + * The caller has just allocated newsk so we can guarantee that other > + * paths won't try to lock it and then oldsk. > + */ > + lock_sock_nested(newsk, SINGLE_DEPTH_NESTING); > sctp_assoc_migrate(assoc, newsk); > > /* If the association on the newsk is already closed before accept() >