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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 401C5C433EF for ; Wed, 29 Sep 2021 14:54:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22F4461440 for ; Wed, 29 Sep 2021 14:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344791AbhI2O4S (ORCPT ); Wed, 29 Sep 2021 10:56:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49306 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344787AbhI2O4S (ORCPT ); Wed, 29 Sep 2021 10:56:18 -0400 Received: from mail-lf1-x132.google.com (mail-lf1-x132.google.com [IPv6:2a00:1450:4864:20::132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A4800C06161C for ; Wed, 29 Sep 2021 07:54:36 -0700 (PDT) Received: by mail-lf1-x132.google.com with SMTP id j5so7065016lfg.8 for ; Wed, 29 Sep 2021 07:54:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=aNDg8rH1IqsEJHwICt9FxmmYGgFjw33LIv8Cr+MhvCs=; b=VFYPi4rv9wgyl4t8uz6CJR4Q7ZjHLJ2oS8yeRT8WjzQvB5Mm4tn4CqGiZi6Lcxt2FT Oym7hvM8rN6crEe6JMre7ZZUqaGTGI0QWaK+jC3F8ZIIwuXQ0zvyEw9PXsP/dvonGW+t jyPb4DeHtEtasd42m/XYhIm1KCy7sPuk6ShXk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=aNDg8rH1IqsEJHwICt9FxmmYGgFjw33LIv8Cr+MhvCs=; b=J2MsMxaEiz303Ye926kSf6ZPBFurm/MbDgRene/ATZMcG26yvtCFOErYOW7nuhH8GB qUAh20pDcNMtpd1yok6QcVN1J398RSSIuuKbbPHMBfRJrTiMwqheIDexF8VWeix/1qzn vQ+L0NWBfbPjAT8Z9C08JHTrXkMC2UitxA9ZlzTEsTASKFZMHn5Xs9L37VCtOQ6qWcnm ZojS1CxYc366GIyKvffi/MhkQdVQWCBGyY89uicXsBFzO2sCzF6yzSmXdPTCJc8CG5eO hhhusoFNfdf4xVvyWJquyGm8ph1gXBPuXrxi7+46NEwYSyH5Ih1gxdkhslRAFP28R2cY Sfqw== X-Gm-Message-State: AOAM530UFn0t+TRNpsUyiVUN+ojTSZlwCU6EE9iEeyxRXZWBiHDkSNvt 4VjlujAECJiVETfU+2JrducELwguRE5IXVB6 X-Google-Smtp-Source: ABdhPJxhhtDFOPKx2lXAci1SHDlKjve3/M20bUBpHPMY1P51HvwIWczAuXj7dKBKNbEyIMWz4tV9nw== X-Received: by 2002:a05:651c:213:: with SMTP id y19mr318077ljn.273.1632927274401; Wed, 29 Sep 2021 07:54:34 -0700 (PDT) Received: from mail-lf1-f43.google.com (mail-lf1-f43.google.com. [209.85.167.43]) by smtp.gmail.com with ESMTPSA id j13sm16442lfm.100.2021.09.29.07.54.31 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Sep 2021 07:54:32 -0700 (PDT) Received: by mail-lf1-f43.google.com with SMTP id i25so11908477lfg.6 for ; Wed, 29 Sep 2021 07:54:31 -0700 (PDT) X-Received: by 2002:a2e:5815:: with SMTP id m21mr329675ljb.95.1632927270683; Wed, 29 Sep 2021 07:54:30 -0700 (PDT) MIME-Version: 1.0 References: <20210928211507.20335-1-mathieu.desnoyers@efficios.com> In-Reply-To: From: Linus Torvalds Date: Wed, 29 Sep 2021 07:54:14 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH] LKMM: Add ctrl_dep() macro for control dependency To: Mathieu Desnoyers Cc: Will Deacon , "Paul E. McKenney" , Peter Zijlstra , Segher Boessenkool , Linux Kernel Mailing List , Alan Stern , Andrea Parri , Boqun Feng , Nick Piggin , David Howells , Jade Alglave , Luc Maranget , Akira Yokosawa , linux-toolchains@vger.kernel.org, linux-arch Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, Sep 29, 2021 at 7:47 AM Linus Torvalds wrote: > > And if there *is* need ("look, we have that same store in both the if- > and the else-statement" or whatever), then say so, and state that > thing. Side note: I'd also like the commit that introduces this to talk very explicitly about the particular case that it is used doe and that it fixes. No "this can happen". A "this happened, here's the _actual_ wrong code generation, and look how this new ctrl_dep() macro fixes it". When it's this subtle, I don't want theoretical arguments. I want actual outstanding and real bugs. Because I get the feeling that there were very few actual realistic examples of this, only made-up theoretical cases that wouldn't ever really be found in real code. Linus