From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0BF8EC433DF for ; Fri, 9 Oct 2020 16:06:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C35872225D for ; Fri, 9 Oct 2020 16:06:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389409AbgJIQGO (ORCPT ); Fri, 9 Oct 2020 12:06:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389144AbgJIQGO (ORCPT ); Fri, 9 Oct 2020 12:06:14 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 32528C0613D2 for ; Fri, 9 Oct 2020 09:06:14 -0700 (PDT) Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94) (envelope-from ) id 1kQuuC-002MvD-Cf; Fri, 09 Oct 2020 18:06:04 +0200 Message-ID: <945d17982b92801dc4a8d61d9fed91e0e60b0105.camel@sipsolutions.net> Subject: Re: [RFC v7 08/21] um: add nommu mode for UML library mode From: Johannes Berg To: Hajime Tazaki Cc: linux-um@lists.infradead.org, jdike@addtoit.com, richard@nod.at, anton.ivanov@cambridgegreys.com, tavi.purdila@gmail.com, linux-kernel-library@freelists.org, linux-arch@vger.kernel.org, retrage01@gmail.com Date: Fri, 09 Oct 2020 18:06:03 +0200 In-Reply-To: (sfid-20201009_053855_635026_E66EA959) References: (sfid-20201009_053855_635026_E66EA959) Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.36.5 (3.36.5-1.fc32) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, 2020-10-09 at 12:38 +0900, Hajime Tazaki wrote: > > > > +++ b/arch/um/nommu/Makefile.um > > > > [...] > > > > > +ifeq ($(shell uname -s), Linux) > > > +NPROC=$(shell nproc) > > > +else # e.g., FreeBSD > > > +NPROC=$(shell sysctl -n hw.ncpu) > > > +endif > > > > That seems very inappropriate here. > > Will cut the FreeBSD part. But even the NPROC and -j flag mangling seems ... awful? > > > --- /dev/null > > > +++ b/arch/um/nommu/include/asm/atomic64.h > > > > That doesn't make sense to me, you can control CONFIG_GENERIC_ATOMIC64 > > to be on, and don't need the ifdef and this file? > > We were suggested to not use GENERIC_ATOMIC64 on 64bit build during > our v3 patchset. So we actually control CONFIG_GENERIC_ATOMIC64 to be > on only when !64BIT, and thus need atomic64.h for the 64BIT build. > > https://lwn.net/ml/linux-arch/20200205093454.GG14879@hirez.programming.kicks-ass.net/ Well, yeah, but your architecture _is_ a piece of crap in needing atomic64 emulation? :-) How about just using the real atomic64 implementation like UML normally does? I mean, falling back to the actual underlying CPU. Or even gcc intrinsics? You've basically re-implemented CONFIG_GENERIC_ATOMIC64, so perhaps you've hidden it from PeterZ's view now because you're no longer touching the real generic atomic64 (which is for 32-bit machines), but that doesn't actually make this any *better*. Arguably *worse* since you've just copied it ... > > > +++ b/arch/um/nommu/um/delay.c > > > > why the double um/ path? > > This is because now in arch/um/Makefile, > > - SUBARCH := um/nommu > - HEADER_ARCH := $(SUBARCH) > - HOST_DIR := arch/$(HEADER_ARCH) > - core-y += $(HOST_DIR)/um > > the last line expands as arch/um/nommu/um. But is there a reason for it? Couldn't it be changed? Anyway, we're still debating the whole build system and layout so not much point in going into the details now ... johannes