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=-5.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 609BCC2D0A8 for ; Wed, 23 Sep 2020 09:55:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24CD62076A for ; Wed, 23 Sep 2020 09:55:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uLypUFcA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726328AbgIWJzI (ORCPT ); Wed, 23 Sep 2020 05:55:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726130AbgIWJzI (ORCPT ); Wed, 23 Sep 2020 05:55:08 -0400 Received: from mail-lf1-x143.google.com (mail-lf1-x143.google.com [IPv6:2a00:1450:4864:20::143]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33C18C0613CE for ; Wed, 23 Sep 2020 02:55:08 -0700 (PDT) Received: by mail-lf1-x143.google.com with SMTP id 77so14064375lfj.0 for ; Wed, 23 Sep 2020 02:55:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version; bh=rZX18Nb4B451H35fKxXNz+FOKZsolDgT7G8y6qr1qK8=; b=uLypUFcA0E5rVNI+RHeLjOrO4R8ls0qGgb1mQ4xXOjxL4P+SVeUDySQixtaLA2ndbU lKcSyW3bD8EfQEQePh+TxLXQHxTA5s9ePEm7DRnXLtO3CcHWhqZqJBUi7rmsPrqW1G3F aCE3b230KvbVW9TzmlxeIa/DQtape50xveN6eMW7kVr2rZsGQ4Gl8V8P3RCmkZHESKfu J2jVGJJQFNAYEwJGbTeSfY+Ze/HzUlJ6JtsJfqdBBk0OgU47cITD9UbcexFrXZGOmdao 7vRp5+KY9kApwJ2iq+ikXE60TBTjqa6Ug80zU7x8A5ddtDqP94hAxuFZvPqGgSh7/zbY czVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version; bh=rZX18Nb4B451H35fKxXNz+FOKZsolDgT7G8y6qr1qK8=; b=GlXsKprWqDl33iauqVVhxrcR83Ga2H9ik27Yq+CzDOAaR2CdoS+UBtQDiO7SQqAlx1 ealbCQOa4Ec5Eeh70AyVU9mjqNPy7VokfsgSR8889zTzIPCdgIITiYjYNtTHoJh1n1gY GmBA2MugOPR9kIMaG7zs5hAPqvRnPadJMhC1Lc8uHvnEcnQ34fvKw0w+IRFbUFJtsWAo swnqLMffztGdGiioXIONvnOn76CR7R1ZCYPR4LDdM7pxRVj2B2cUc75MbD8kIAmRplkC dOPpyNkO2ns2lvWLJa9CwqwJAx18aI2QjsWr1lrDJFljyASjIRvrugyyAsvmQ+2UnMNY TwAw== X-Gm-Message-State: AOAM5314Z4mwGkjofQFWGGnODjhUrsJFW7ZgcgB63Xn9x+TD3KwysXE1 IvjMYTr0fxMrY459lmlavlY= X-Google-Smtp-Source: ABdhPJyFeme2PzRuZLADYLxEONkLoODcIN2LPNtvFAqYLkEDt5nJjxLqw/RieypMiZXXaxpboW4iuA== X-Received: by 2002:a05:6512:3606:: with SMTP id f6mr3398610lfs.282.1600854906538; Wed, 23 Sep 2020 02:55:06 -0700 (PDT) Received: from eldfell ([194.136.85.206]) by smtp.gmail.com with ESMTPSA id 78sm4635269lfi.81.2020.09.23.02.55.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2020 02:55:06 -0700 (PDT) Date: Wed, 23 Sep 2020 12:55:02 +0300 From: Pekka Paalanen To: Daniel Vetter Cc: Intel Graphics Development , DRI Development , Daniel Stone , Simon Ser , stable , Ville =?UTF-8?B?U3lyasOkbMOk?= , Daniel Vetter Subject: Re: [PATCH] drm: document and enforce rules around "spurious" EBUSY from atomic_commit Message-ID: <20200923125502.4735f720@eldfell> In-Reply-To: References: <20200922181834.2913552-1-daniel.vetter@ffwll.ch> <20200923111717.68d9eb51@eldfell> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/HSKGjOiwSV7m_k8F45bc62z"; protocol="application/pgp-signature" Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org --Sig_/HSKGjOiwSV7m_k8F45bc62z Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 23 Sep 2020 11:26:39 +0200 Daniel Vetter wrote: > I'm really not awake yet ... >=20 > On Wed, Sep 23, 2020 at 10:17 AM Pekka Paalanen wro= te: > > > > On Tue, 22 Sep 2020 20:18:34 +0200 > > Daniel Vetter wrote: > > =20 > > > When doing an atomic modeset with ALLOW_MODESET drivers are allowed to > > > pull in arbitrary other resources, including CRTCs (e.g. when > > > reconfiguring global resources). > > If yes, and *if* userspace is single-threaded wrt. to KMS updates, > > that might offer a way to work around it in userspace. But if userspace > > is flipping other CRTCs from other threads, TEST_ONLY commit does not > > help because another thread may cut in and make a CRTC busy. =20 >=20 > This is not a legit programming model for atomic. An atomic commit is > always relative to the current state. If that state changes, then you > need to re-run your TEST_ONLY commit. So multiple threads changing > state in parallel isn't really a good idea anyway. Minimally we'd need > some kind of TEST_ONLY pile-up, so you can validate a change assuming > another commit has already happened. That's even harder than deep > queues on the commit side, we'd probably need full rollback of > commits. Yes, very good point. I forgot that for a moment. 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