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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F288DC982CC for ; Sun, 20 Sep 2026 03:46:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=DVq+syVABeKyOurh3QCdSWgniSrDIfsTXqEF8Z94hRc=; b=u1DqJpAsEts+WE 3K1qI4FNLW8kcRMYUnjE9XyvHiB7/s9d2cKbtjlfBZVqz+uMu8l7erwFgRO88+mVYbJ6h3sCnd5/X 3pTX5VH12N1NoIjvVQiJqhlb9A2HeAcNIN+jcgqPsBj5twbtLm5Buc3UHhzLY04d7POD4Y+sFf27l 55hAxraaR53O2DGQ8Kb7mdESWXDCHtAZhktaHKgrJ+Ru58abSYBKHAaH4uxzV0r1jCsS5oBLBPO2K jVzHp2G1XBAQCAyWpO50cOM8mnPiD/abRl/NnGgWSvlVheThzttzVmz0tTbt6BTiyCDK7Y/qiGjJo rUrbb9DcRgCxksP/CUZA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x88Vq-0000000GpeD-0IXB; Sun, 20 Sep 2026 03:46:46 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x88Vo-0000000Gpdu-0gk2; Sun, 20 Sep 2026 03:46:44 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 9B536601FD; Sun, 20 Sep 2026 03:46:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F2021F000FF; Sun, 20 Sep 2026 03:46:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789876002; bh=RAgjdNuY0GHwXBswA5NShTSJab25cAeZ2wGxG0I/vUo=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=Pq1c/x2eNDaaA3FhHkOhGuCnsEwXECeh01hVEHOpDv8HFPU3D8PLxh2wVU0nylDaJ 7EaPp5slBBZUiOqsjhzEs7IgscKJPgdM3bXnpCs8IVuHJRaG5hD0rrtfwkhInaUah2 UEwXWAbH8m3JDS27foafZhT7dYncShEItD34AqEMdXClbdFXPJauYFWvvxe4hWYd96 N8ZnwsnLY9Xqn+sIDhK7K9lW5wcmPeM+9vJTKsXnZtJMmVVGCpp7vNL+wlt5H2W4zk L6Y0Pud3rjcJlvf9NtFTivJRz4pQVpslkC4pi8p+/DINuR9TeguqodaZGqQrIxp572 Ic8aE8TCrC2FA== Date: Sat, 19 Sep 2026 20:46:42 -0700 From: Kees Cook To: "Lorenzo Stoakes (ARM)" Cc: Linus Torvalds , Nathan Chancellor , Nicolas Schier , Nick Desaulniers , Bill Wendling , Justin Stitt , Masahiro Yamada , Alexey Gladkov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Arnd Bergmann , Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , Ilias Apalodimas , Josh Poimboeuf , Peter Zijlstra , Miguel Ojeda , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , Onur =?iso-8859-1?Q?=D6zkan?= , Jonathan Corbet , Randy Dunlap , "Gustavo A. R. Silva" , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-efi@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-doc@vger.kernel.org, Jens Axboe , linux-hardening@vger.kernel.org Subject: Re: [PATCH v3 09/20] kbuild: implement and use depcheck to check dependency timestamps Message-ID: <202609192045.24A5A4E876@keescook> References: <20260917-build-speedup-v3-0-9ecf4163ff36@kernel.org> <20260917-build-speedup-v3-9-9ecf4163ff36@kernel.org> <202609171117.35BFDCC13@keescook> <202609171229.31BB336E1@keescook> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Sat, Sep 19, 2026 at 06:02:46PM +0100, Lorenzo Stoakes (ARM) wrote: > On Thu, Sep 17, 2026 at 01:59:26PM -0700, Kees Cook wrote: > > So, yeah, it makes me nervous, and it may make incremental builds less > > idempotent. But I can't really find extant problems and the demo is > > slightly contrived, but not exactly an impossible situation. > > Ack thanks for this! > > There is definitely an issue here, your example is fine in the stock kernel > but one run late in v3. > > Solution is to have depcheck treat any dependency that is itself a target > of the same run as never being 'fresh' (it already reads every .cmd file in > the directory so has all the dependency information it needs), so that's > fixed in v4. > > Confirmed that it fixes the demo'd bug here, that touching a header > rebuilds exactly the same objects as it did before and that noop build perf > was not harmed by the change. Oh very nice! Thank you for finding a solution there. :) -- Kees Cook _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv