From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 1 May 2001 13:33:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 1 May 2001 13:33:10 -0400 Received: from penguin.e-mind.com ([195.223.140.120]:33842 "EHLO penguin.e-mind.com") by vger.kernel.org with ESMTP id ; Tue, 1 May 2001 13:32:53 -0400 Date: Tue, 1 May 2001 19:32:25 +0200 From: Andrea Arcangeli To: kuznet@ms2.inr.ac.ru Cc: davem@redhat.com, ralf@nyren.net, linux-kernel@vger.kernel.org Subject: Re: 2.4.4: Kernel crash, possibly tcp related Message-ID: <20010501193225.D31373@athlon.random> In-Reply-To: <20010501190942.B31373@athlon.random> <200105011725.VAA00484@ms2.inr.ac.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200105011725.VAA00484@ms2.inr.ac.ru>; from kuznet@ms2.inr.ac.ru on Tue, May 01, 2001 at 09:25:43PM +0400 X-GnuPG-Key-URL: http://e-mind.com/~andrea/aa.gnupg.asc X-PGP-Key-URL: http://e-mind.com/~andrea/aa.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 01, 2001 at 09:25:43PM +0400, kuznet@ms2.inr.ac.ru wrote: > Hello! > > > zero and we are running in such slow path, it is obvious the send_head > > _was_ NULL when we entered the critical section, so it's perfectly fine > > It is not only not obvious, it is not true almost always. > On normally working tcp send_head is almost never NULL, > it is NULL only when application is so slow that is not able > to saturate pipe. If you do not believe my word, add printk checking this. 8) Note: I said: ".. if send_head points to skb and skb->len is ^^^^^^^^^^^^^^^^^^^^^^^^^^ zero and we are running in such slow path ..". If send_head doesn't point to skb then it is before it (and it cannot advance under us of course because we hold the sock lock) and so in such case we didn't clobbered the send_head at all in skb_entail, and so we don't need to touch send_head in order to undo (we only need to unlink). See? Andrea