From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751791AbeCNWJO (ORCPT ); Wed, 14 Mar 2018 18:09:14 -0400 Received: from mail-qk0-f170.google.com ([209.85.220.170]:33181 "EHLO mail-qk0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751279AbeCNWJM (ORCPT ); Wed, 14 Mar 2018 18:09:12 -0400 X-Google-Smtp-Source: AG47ELvX8a1ETkJbLqjVHcNakCkubl15kBQrAwJAAo53XNPpsE8lXexffedF7eP5u8cYojlLU7K5jQ== Date: Wed, 14 Mar 2018 15:09:09 -0700 From: Tejun Heo To: Andrew Morton Cc: Kirill Tkhai , cl@linux.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org 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> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: 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