From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751375AbaCQXSw (ORCPT ); Mon, 17 Mar 2014 19:18:52 -0400 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:39874 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750733AbaCQXSu (ORCPT ); Mon, 17 Mar 2014 19:18:50 -0400 Date: Mon, 17 Mar 2014 23:18:14 +0000 From: One Thousand Gnomes To: Andrew Morton Cc: Joseph Salisbury , penguin-kernel@I-love.SAKURA.ne.jp, Oleg Nesterov , rientjes@google.com, Linus Torvalds , tj@kernel.org, Thomas Gleixner , LKML , Kernel Team Subject: Re: [v3.13][v3.14][Regression] kthread: make kthread_create() killable Message-ID: <20140317231814.3249e6d2@alan.etchedpixels.co.uk> In-Reply-To: <20140317130241.7e4fde86d75d417628da6f1a@linux-foundation.org> References: <53236AA2.7030105@canonical.com> <20140317130241.7e4fde86d75d417628da6f1a@linux-foundation.org> Organization: Intel Corporation X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.20; 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 > Root cause time: it's wrong for the oom-killer to use SIGKILL. In fact It has to use SIGKILL anything else might be caught and grow the user stack a page.. > it's basically always wrong to send signals from in-kernel. Signals > are a userspace IPC mechanism and using them in-kernel a) makes it hard > (or impossible) to distinguish them from userspace-originated signals Actually signals are a kernel messaging system someone repurposed for IPC. > and b) permits userspace to produce surprising results in the kernel, > which I suspect is what we're seeing here. There is enough information for kernel side code to decide whether a signal came from kernel or userspace. Then again - it's not clear that it should ever have to. Alan