From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755728AbYEZQYK (ORCPT ); Mon, 26 May 2008 12:24:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753847AbYEZQXx (ORCPT ); Mon, 26 May 2008 12:23:53 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:51366 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753712AbYEZQXw (ORCPT ); Mon, 26 May 2008 12:23:52 -0400 Date: Mon, 26 May 2008 18:23:28 +0200 From: Ingo Molnar To: Ilpo =?iso-8859-1?Q?J=E4rvinen?= Cc: LKML , Netdev , "David S. Miller" , "Rafael J. Wysocki" , Andrew Morton Subject: Re: [bug] stuck localhost TCP connections, v2.6.26-rc3+ Message-ID: <20080526162328.GA9089@elte.hu> References: <20080526115628.GA31316@elte.hu> <20080526135940.GB24870@elte.hu> <20080526141252.GA31352@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ilpo Järvinen wrote: > On Mon, 26 May 2008, Ingo Molnar wrote: > > > there's a hung distcc task on the system, waiting for socket action > > forever: > > > > [root@europe ~]# strace -fp 19578 > > Process 19578 attached - interrupt to quit > > select(5, NULL, [4], [4], {82, 90000} > > Hmm, readfds is NULL isn't it?!? Are you sure you straced the right > process? yes, i'm stracing the task that is hung unexpectedly. > > disturbing that task via strace did not change the state of the > > socket - and that's not unexpected as it's a select(). [TCP state > > might be affected if strace impacted a recvmsg or a sendmsg wait > > directly.] > > I fail to understand this paragraph due to excessive negation... :-) i mean, sometimes a TCP connection can get 'unstuck' if you strace a task - that is because the TCP related syscall the task sits in gets interrupted. But in this case it's select() which doesnt explicitly take the socket, doesnt do any tcp_push_pending_frames() processing, etc. - it just its on the socket waitqueue AFAICS. And that's expected. Ingo