From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755131Ab1HCNdz (ORCPT ); Wed, 3 Aug 2011 09:33:55 -0400 Received: from mail-vx0-f174.google.com ([209.85.220.174]:57158 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753495Ab1HCNdr (ORCPT ); Wed, 3 Aug 2011 09:33:47 -0400 MIME-Version: 1.0 In-Reply-To: <20110803131323.GC2773@nautilus.holoscopio.com> References: <20110803113033.1c3c6960@taxman.wild-wind.fr.eu.org> <20110803131323.GC2773@nautilus.holoscopio.com> From: Kay Sievers Date: Wed, 3 Aug 2011 15:33:27 +0200 Message-ID: Subject: Re: [PATCH] shm: fix a race between shm_exit() and shm_init() To: Thadeu Lima de Souza Cascardo Cc: linux-kernel@vger.kernel.org, marc.zyngier@arm.com, manuel.lauss@googlemail.com, torvalds@linux-foundation.org, akpm@linux-foundation.org, segoon@openwall.com, richard@nod.at, gregkh@suse.de Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 3, 2011 at 15:13, Thadeu Lima de Souza Cascardo wrote: > As Marc Zyngier has pointed out, the culprit is driver_init, which > calls devices_init. I'd say other calls from driver_init also call into > kset and kobject, which will dispatch uevent helper. > > I tried to reproduce the problem using UML and only was successful after > setting CONFIG_UEVENT_HELPER_PATH. I guess we could obsolete this > feature and plan its removal soon. Is anybody still using this? Forking binaries from the kernel for frequent events is something fundamentally wrong to do. It is not even rate-limited or has any upper bounds. It is known to create out-of-memory situations on machines with many devices and tiny RAM. Configs that virtualizations with many guests use pretty often. They can not even bootup with /sbin/hotplug enabled then. It would be nice to remove that broken thing, no common system or distro uses it since quite some years now. But I wouldn't be surprised if some people still use it for whatever hack they need locally. Kay