From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B6EEC04AA5 for ; Mon, 15 Oct 2018 13:37:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4ED9F2083C for ; Mon, 15 Oct 2018 13:37:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4ED9F2083C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=iki.fi Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726635AbeJOVXR (ORCPT ); Mon, 15 Oct 2018 17:23:17 -0400 Received: from emh07.mail.saunalahti.fi ([62.142.5.117]:48478 "EHLO emh07.mail.saunalahti.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726400AbeJOVXR (ORCPT ); Mon, 15 Oct 2018 17:23:17 -0400 Received: from ydin.reaktio.net (reaktio.net [85.76.255.15]) by emh07.mail.saunalahti.fi (Postfix) with ESMTP id 1B2A1B00B2; Mon, 15 Oct 2018 16:37:52 +0300 (EEST) Received: by ydin.reaktio.net (Postfix, from userid 1001) id 03FD736C0F6; Mon, 15 Oct 2018 16:37:52 +0300 (EEST) Date: Mon, 15 Oct 2018 16:37:51 +0300 From: Pasi =?iso-8859-1?Q?K=E4rkk=E4inen?= To: Mikulas Patocka Cc: Dmitry Safonov , linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Daniel Axtens , Dmitry Vyukov , Mark Rutland , Michael Neuling , Nathan March , Peter Hurley , Peter Zijlstra , "Rong, Chen" , Sergey Senozhatsky , Tan Xiaojun , Tetsuo Handa , stable@vger.kernel.org, Greg Kroah-Hartman , Jiri Slaby , Jiri Slaby , syzbot+3aa9784721dfb90e984d@syzkaller.appspotmail.com Subject: Re: [PATCHv5 0/7] tty: Hold write ldisc sem in tty_reopen() Message-ID: <20181015133751.GO5318@reaktio.net> References: <20180917235258.5719-1-dima@arista.com> <1537379148.21380.16.camel@arista.com> <1537388512.21380.44.camel@arista.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Thu, Sep 20, 2018 at 10:25:01AM -0400, Mikulas Patocka wrote: > > > On Wed, 19 Sep 2018, Dmitry Safonov wrote: > > > On Wed, 2018-09-19 at 16:03 -0400, Mikulas Patocka wrote: > > > > > > On Wed, 19 Sep 2018, Dmitry Safonov wrote: > > > > Thanks much for the testing, Mikulas. > > > > Could you try to bisect which of the patches causes it? > > > > The most important are 1,2,3 - probably, one of them caused it.. > > > > I'll stare a bit into the code. > > > > > > The patch 3 causes it. > > > > > > The hangs during reboot take either 80 seconds, 3 minutes or 3:25. > > > > Thanks much for that again. > > Any chance you have sysrq enabled and could print: locks held in system > > and kernel backtraces for applications? > > Stacktrace doesn't work on parisc. It used to work on 4.18, but the kernel > 4.19 reportedly requires patched binutils. > > Mikulas > > > I suppose, userspace hangs in n_tty_receive_buf_common(), which is > > better of cause than null-ptr dereference, but I believe we can improve > > it by stopping a reader earlier if there is any writer pending. > > > > -- > > Thanks, > > Dmitry > > Any progress here? Or is more info/stacktrace needed about the hang? Thanks, -- Pasi