From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934749AbbKSXKE (ORCPT ); Thu, 19 Nov 2015 18:10:04 -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 S1758294AbbKSXKB (ORCPT ); Thu, 19 Nov 2015 18:10:01 -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> <564CE3DA.8040404@nod.at> 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: <564E56C2.2050704@nod.at> Date: Fri, 20 Nov 2015 00:09:54 +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: <564CE3DA.8040404@nod.at> 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 21:47 schrieb Richard Weinberger: > 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. Did some research. It is not that bad. It broke in v3.5 because of this commit: commit 68f3f16d9ad0f1e28ab3fd0001ab5798c41f15a3 Author: Al Viro Date: Mon May 21 21:42:32 2012 -0400 new helper: sigsuspend() guts of saved_sigmask-based sigsuspend/rt_sigsuspend. Takes kernel sigset_t *. Open-coded instances replaced with calling it Thanks, //richard