From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752238AbeCPSnz (ORCPT ); Fri, 16 Mar 2018 14:43:55 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:51456 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750991AbeCPSny (ORCPT ); Fri, 16 Mar 2018 14:43:54 -0400 Date: Fri, 16 Mar 2018 11:43:48 -0700 From: Darren Hart To: Dominik Brodowski Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, luto@kernel.org, mingo@kernel.org, akpm@linux-foundation.org, arnd@arndb.de, Thomas Gleixner , Ingo Molnar , Peter Zijlstra Subject: Re: [PATCH v2 03/36] mm: use do_futex() instead of sys_futex() in mm_release() Message-ID: <20180316184348.GA20184@localhost.localdomain> References: <20180315190529.20943-1-linux@dominikbrodowski.net> <20180315190529.20943-4-linux@dominikbrodowski.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180315190529.20943-4-linux@dominikbrodowski.net> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2018 at 08:04:56PM +0100, Dominik Brodowski wrote: > sys_futex() is a wrapper to do_futex() which does not modify any > values here: > > - uaddr, val and val3 are kept the same > > - op is masked with FUTEX_CMD_MASK, but is always set to FUTEX_WAKE. > Therefore, val2 is always 0. > > - as utime is set to NULL, *timeout is NULL > > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Darren Hart > Cc: Andrew Morton > Signed-off-by: Dominik Brodowski Hi Dominik, I'm missing the "why" part here. What is it you are trying to address? do_futex is not currently in use outside of the futex implementation, while sys_futex is. This decouples the interface from the implementation. While this is perhaps less critical within the kernel, I don't see a compelling reason to increase the coupling between the mm and futex implementations. Without a compelling WHY, Nack from me. -- Darren Hart VMware Open Source Technology Center