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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0531C433EF for ; Sat, 8 Jan 2022 15:16:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233902AbiAHPQN (ORCPT ); Sat, 8 Jan 2022 10:16:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229455AbiAHPQK (ORCPT ); Sat, 8 Jan 2022 10:16:10 -0500 Received: from mail-wr1-x42f.google.com (mail-wr1-x42f.google.com [IPv6:2a00:1450:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5ED92C06173F; Sat, 8 Jan 2022 07:16:09 -0800 (PST) Received: by mail-wr1-x42f.google.com with SMTP id k18so17123543wrg.11; Sat, 08 Jan 2022 07:16:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=uucTvtg1YQMjIP0qoj4ZoGgmtYYbV+cou28W1zzliws=; b=A1k4VDrvuCebTVmunqofPKMOGmzg8ckI4u3okugvYNraxLKTbhFLXWZtX7al2ZBWel C2IDdncztk9+bTxGS2CMcIEC90FjXYHJsK57rvHjnmtL7dZ4ni+XGGQZqRKMDVbXwA+I A/qubHWE6yhjNFLpJ1nYxOZQN6lv9ZSARxmH6lAQmEFGA//nsrVdt/ZBjTWCbbpcIyiF AiINtrv/KEXVOYUvxi0YePELa1aR+mjbX+MyRUeN2iWv5v7zHY00adHqWoMZ1w6AIwYG yAdo/e6WAPwgaCMemGqmu4n6agyA3tzb2nfcWhD/PWFk808VK5QR8afc0hN0nFBbsGrl B0Uw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=uucTvtg1YQMjIP0qoj4ZoGgmtYYbV+cou28W1zzliws=; b=T5DoO3DMvaqyNN8zkuJHEiNJyimtWFn1w1AvDki8HkanFtu5FKbo81j7e4sI19dOd9 BKH1YUAU7KPJMtSbGojc8SwDR7xX6KjN2pb5E/KfakF7FbVI1WI8hgTWHoxXlf7P49xS 3BY2H9nvAbc7RluWdluMR8jLch0E6sqpx+nHB22GgjJQrpNFDsUXDjq30pwW+hbJwxOT keuTV1uzN2DCg423aqWCHbSAOEiFAiIobrK81BzgS4Ec21Drd3hBXdHUAkerwi8AwMI7 2MGsWQZGRGyqa8xNOw9OSCCqfxd14DtaoM/GbP/x+mBm27Y/oDVwpsv4GVmwLP8qd+yS GxCg== X-Gm-Message-State: AOAM532/T/E+hOk2oXp0xFFrYhHQAsxAXPEj+GMtlDxVrLd6TGQ/yU2R xRXX/6BZuUuxBzGw11+E2E3SIl0mlXM= X-Google-Smtp-Source: ABdhPJwLiHYa3upjIY0klY4+zWxYl5EZgcOkEErx4i8nnXRKMGzyDpAok+0VJvZ5yqbi98eRiZYTTQ== X-Received: by 2002:a5d:6d0a:: with SMTP id e10mr58254890wrq.65.1641654967930; Sat, 08 Jan 2022 07:16:07 -0800 (PST) Received: from gmail.com (84-236-113-171.pool.digikabel.hu. [84.236.113.171]) by smtp.gmail.com with ESMTPSA id o29sm3109607wms.3.2022.01.08.07.16.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Jan 2022 07:16:07 -0800 (PST) Sender: Ingo Molnar Date: Sat, 8 Jan 2022 16:16:05 +0100 From: Ingo Molnar To: Nathan Chancellor Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Andrew Morton , Peter Zijlstra , Thomas Gleixner , Greg Kroah-Hartman , "David S. Miller" , Ard Biesheuvel , Josh Poimboeuf , Jonathan Corbet , Al Viro , llvm@lists.linux.dev Subject: Re: [PATCH 0000/2297] [ANNOUNCE, RFC] "Fast Kernel Headers" Tree -v1: Eliminate the Linux kernel's "Dependency Hell" Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Nathan Chancellor wrote: > I tried to checkout at 9006a48618cc0cacd3f59ff053e6509a9af5cc18 to see if > I could reproduce that breakage there but the build errors out at that > change (I do see notes of bisection breakage in some of the commits) so I > assume that is expected. Yeah, so the underlying problem is that these two commits want to be a single commit: # Commit #117 headers/deps: Move task->thread_info to per_task() # Commit #106 headers/deps: Move thread_info APIs to As we can only switch ARM64's to use per_task() - which requires - if we first fix & simplify 's header dependencies, which is done to a sufficient level by: # Commit #556 headers/deps: Optimize dependencies, remove inclusion So it's a catch-22, and quite a complication, and a bisection breakage distance of ~450 commits, with a lot of ordering assumptions & conflicts along the way, should we attempt to move the first two to later stages. :-/ But today I've restructured the tree, and the -v2-to-be tree is now fully bisectable on ARM64 too. :-) There's a single, late per_cpu() conversion commit, after the first phase of simplifications: headers/deps: Move task->thread_info to per_task() I'd guess that either this one is that breaks SCS for you, or the ::thread conversion: headers/deps: per_task, arm64, x86: Convert task_struct::thread to a per_task() field I've pushed out these fixes to the sched/headers branch a couple of minutes ago, and this will be part of the -v2 release as well. Thanks, Ingo