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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 985C6C433E7 for ; Fri, 9 Oct 2020 16:02:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 37E4F2227F for ; Fri, 9 Oct 2020 16:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389252AbgJIQCT (ORCPT ); Fri, 9 Oct 2020 12:02:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389135AbgJIQCT (ORCPT ); Fri, 9 Oct 2020 12:02:19 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 946D3C0613D2 for ; Fri, 9 Oct 2020 09:02:19 -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 1kQuqT-002Mlq-Mk; Fri, 09 Oct 2020 18:02:13 +0200 Message-ID: Subject: Re: [RFC v7 07/21] um: extend arch_switch_to for alternate SUBARCH 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 18:02:12 +0200 In-Reply-To: (sfid-20201009_032432_010821_E55BA25D) References: <5502f24bcdc07372fbc5ee86c700770038b041c4.camel@sipsolutions.net> (sfid-20201009_032432_010821_E55BA25D) 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 10:24 +0900, Hajime Tazaki wrote: > On Thu, 08 Oct 2020 00:25:06 +0900, > Johannes Berg wrote: > > On Tue, 2020-10-06 at 18:44 +0900, Hajime Tazaki wrote: > > > This commit introduces additional argument of previous task when > > > context switch happens. New SUBARCH can use the new information to > > > switch tasks in a subarch-specific manner. > > > > > > The patch is particularly required by nommu mode implemented as a > > > SUBARCH of UML. > > > > Would probably be good to already say why here? > > Agree. > > The patch is particularly required by nommu mode because it uses > previous task information to control the previous thread (e.g., down > semaphore, terminate thread, clean up thread flags). > > Something like this ? Well, still not sure I like "nommu" to refer to "library mode", but I'm also not sure that you can understand that without the context of how threads actually work in library mode? Maybe even something vague like Having access to the previous thread will be required in library mode for it to implement thread switching correctly. would give some rationale? johannes