From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756897AbbKRUo3 (ORCPT ); Wed, 18 Nov 2015 15:44:29 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:46449 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754683AbbKRUo2 (ORCPT ); Wed, 18 Nov 2015 15:44:28 -0500 Date: Wed, 18 Nov 2015 12:44:26 -0800 From: Andrew Morton To: Richard Weinberger 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 Subject: Re: [PATCH] signal: Unexport sigsuspend() Message-Id: <20151118124426.a5d89714ec7102e8066af4e7@linux-foundation.org> In-Reply-To: <1447697901-28918-1-git-send-email-richard@nod.at> References: <1447697901-28918-1-git-send-email-richard@nod.at> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?