From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933575AbbKRUrh (ORCPT ); Wed, 18 Nov 2015 15:47:37 -0500 Received: from a.ns.miles-group.at ([95.130.255.143]:11949 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754683AbbKRUr3 (ORCPT ); Wed, 18 Nov 2015 15:47:29 -0500 Subject: Re: [PATCH] signal: Unexport sigsuspend() To: Andrew Morton References: <1447697901-28918-1-git-send-email-richard@nod.at> <20151118124426.a5d89714ec7102e8066af4e7@linux-foundation.org> Cc: linux-kernel@vger.kernel.org, vegard.nossum@oracle.com, oleg@redhat.com, amanieu@gmail.com, dave@stgolabs.net, qiaowei.ren@intel.com, luto@amacapital.net, palmer@dabbelt.com, vdavydov@parallels.com From: Richard Weinberger Message-ID: <564CE3DA.8040404@nod.at> Date: Wed, 18 Nov 2015 21:47:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20151118124426.a5d89714ec7102e8066af4e7@linux-foundation.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 18.11.2015 um 21:44 schrieb Andrew Morton: > On Mon, 16 Nov 2015 19:18:21 +0100 Richard Weinberger wrote: > >> sigsuspend() is nowhere used except in signal.c itself, >> so we can mark it static do not pollute the global namespace. >> >> But this patch is more than a boring cleanup patch, >> it fixes a real issue on UserModeLinux. >> UML has a special console driver to display ttys using xterm, >> or other terminal emulators, on the host side. >> Vegard reported that sometimes UML is unable to spawn a xterm >> and he's facing the following warning: >> WARNING: CPU: 0 PID: 908 at include/linux/thread_info.h:128 sigsuspend+0xab/0xc0() >> It turned out that this warning makes absolutely no sense as >> the UML xterm code calls sigsuspend() on the host side, at least it tries. >> But as the kernel itself offers a sigsuspend() symbol the linker choose >> this one instead of the glibc wrapper. Interestingly this code used to >> work since ever but always blocked signals on the wrong side. >> Some recent kernel change made the WARN_ON() trigger and uncovered the bug. >> > > So we don't know what caused this or when it started happening. hrm. > I guess I'll stick a cc:stable in there as it's likely to affect 4.3 > and perhaps earlier, OK? I fear it has been this way for ever. CC'ing stable is a good idea! Thanks, //richard