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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 D8462C43387 for ; Fri, 11 Jan 2019 18:33:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AFB0D20872 for ; Fri, 11 Jan 2019 18:33:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=pobox.com header.i=@pobox.com header.b="jyHoWA2N"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=fluxnic.net header.i=@fluxnic.net header.b="cpizkqld" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390053AbfAKSdT (ORCPT ); Fri, 11 Jan 2019 13:33:19 -0500 Received: from pb-smtp2.pobox.com ([64.147.108.71]:55948 "EHLO pb-smtp2.pobox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732979AbfAKSdS (ORCPT ); Fri, 11 Jan 2019 13:33:18 -0500 Received: from pb-smtp2.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 7A1A013063A; Fri, 11 Jan 2019 13:33:13 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=date:from:to :cc:subject:message-id:mime-version:content-type; s=sasl; bh=X4H 2bcYWNLqtXC5emIJfjgZruI8=; b=jyHoWA2Nfn1qGyar4bJES1VHRJ2k5A8dWZ0 ZNtxYMBXSMySg/Uapbu/9PTDUix0NapuitH+p4Hu5oMf1GZOvSItKtb1WULUwTtk YnjSNZ4aU/YXWzcLnMWr6fqULms02qziwBKWd83NB9/dk3lm91TQE8dBaP1Jrzt2 ed0QBIY4= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 715E5130639; Fri, 11 Jan 2019 13:33:13 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=fluxnic.net; h=date:from:to:cc:subject:message-id:mime-version:content-type; s=2016-12.pbsmtp; bh=nu9g/Ge59NXEgOqatWTIi9YnE6UKg67uTNcjWgLrszE=; b=cpizkqldwg9OOiwVGWvPzsdQplKLCthtWqPrbY4FLa73vxgpZcs9/jLaOJgk9AOpE+NACGHFyyoVoo3V0gHXdl8wU8V87QVRkEDvyIl6g/1JJC3pWDZ/iEMbf2ypbQX2kjPDOlnRFylbAUQntY0VlsEmaVHpP9naEHiE+c5XAbU= Received: from yoda.home (unknown [70.82.104.228]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id D3991130636; Fri, 11 Jan 2019 13:33:12 -0500 (EST) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTPSA id C3C8E2DA0173; Fri, 11 Jan 2019 13:33:11 -0500 (EST) Date: Fri, 11 Jan 2019 13:33:09 -0500 (EST) From: Nicolas Pitre To: Dmitry Safonov , Greg Kroah-Hartman , Jiri Slaby cc: Mark Rutland , Tetsuo Handa , Tycho Andersen , Dave Mielke , linux-kernel@vger.kernel.org Subject: commit 83d817f410 broke my ability to use Linux with a braille display Message-ID: User-Agent: Alpine 2.21 (LFD 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Pobox-Relay-ID: 5A4BA7E2-15CF-11E9-B3C0-84B4F54BB12D-78420484!pb-smtp2.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I use Linux with the help of a braille display and the brltty daemon. It turns out that the latest mainline kernel I can work with comes from commit 231f8fd0cc. Anything past that and I lose the ability to read the console barely a few seconds after the system has booted as brltty is thrown a wrench and the braille display becomes completely inoperable. Things get somewhat better with commit c96cf923a9 as brltty is not longer incapacitated, but some programs would randomly crash. Even the very first login attempt won't work as I soon as I hit enter after my user name the password prompt is skipped over, just like if the enter key had been hit twice. Then lynx (the text web browser) would crash as soon as I switch the virtual console with LeftAlt+FN. Mind you, this isn't easy to perform bisection in those conditions. And the worst commit i.e. 83d817f410 is marked for stable! :-( Some interaction with brltty must be at play here otherwise such breakage would never have survived up to the mainline kernel. As far as latest mainline is concerned, I managed to reproduce at least one of the unwelcome behavior change (hoping that's all there is to this issue) with a very simple test case so you won't have to learn braille to debug this: # from any vt, make sure tty40 is allocated and empty openvt -c 40 -f -- true # open it and wait on read() cat /dev/tty40 # from a second vt, simply open tty40 again true < /dev/tty40 # come back to the first vt and watch cat bailing out with EAGAIN. Please fix. Nicolas