From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id 0CF7B6B0009 for ; Wed, 14 Mar 2018 18:09:31 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id e6so3086171qkf.19 for ; Wed, 14 Mar 2018 15:09:31 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id u90sor2425564qku.144.2018.03.14.15.09.12 for (Google Transport Security); Wed, 14 Mar 2018 15:09:12 -0700 (PDT) Date: Wed, 14 Mar 2018 15:09:09 -0700 From: Tejun Heo Subject: Re: [PATCH] percpu: Allow to kill tasks doing pcpu_alloc() and waiting for pcpu_balance_workfn() Message-ID: <20180314220909.GE2943022@devbig577.frc2.facebook.com> References: <152102825828.13166.9574628787314078889.stgit@localhost.localdomain> <20180314135631.3e21b31b154e9f3036fa6c52@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180314135631.3e21b31b154e9f3036fa6c52@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Kirill Tkhai , cl@linux.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Hello, Andrew. On Wed, Mar 14, 2018 at 01:56:31PM -0700, Andrew Morton wrote: > It would benefit from a comment explaining why we're doing this (it's > for the oom-killer). Will add. > My memory is weak and our documentation is awful. What does > mutex_lock_killable() actually do and how does it differ from > mutex_lock_interruptible()? Userspace tasks can run pcpu_alloc() and I IIRC, killable listens only to SIGKILL. > wonder if there's any way in which a userspace-delivered signal can > disrupt another userspace task's memory allocation attempt? Hmm... maybe. Just honoring SIGKILL *should* be fine but the alloc failure paths might be broken, so there are some risks. Given that the cases where userspace tasks end up allocation percpu memory is pretty limited and/or priviledged (like mount, bpf), I don't think the risks are high tho. Thanks. -- tejun