From patchwork Thu Feb 24 12:59:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 12758522 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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (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 06E15C433EF for ; Thu, 24 Feb 2022 12:59:43 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E94D610F372; Thu, 24 Feb 2022 12:59:42 +0000 (UTC) Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by gabe.freedesktop.org (Postfix) with ESMTPS id E25A010F370 for ; Thu, 24 Feb 2022 12:59:41 +0000 (UTC) Received: by mail-ej1-x632.google.com with SMTP id lw4so4101175ejb.12 for ; Thu, 24 Feb 2022 04:59:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=wlCwHRZWI6fqCrBqATh916lDw0CxOebXEub0NpEWvbQ=; b=d/GOruU2xzHT1fNaKMdDaLRG3X6CVxzKxieY7cXTTQ/jE1QSUxncdvyY+ndPadNSuB pYZ4/x2YCRRPK44PY92BTxg6+jE4Qq+03VXVn7HNpQkHWIlXd+NXpDOTKb+HcLe/xoyb ha1cUsJ0ce1vxOKSvf2a83rO+fH6NvHFJCHU8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=wlCwHRZWI6fqCrBqATh916lDw0CxOebXEub0NpEWvbQ=; b=m76O1YVWvKVOVyEwygNiGfPRQZnDcjr1UVCItCggKC7mEz8iNi0P4a5sULm80SuK/Q qJgFbzti3vTvWtbdFOOk6+WIniECFPtz14L6VOihLHmlreCNOL+VGRYvZGOJejZ1ofzo sudNgqbi/hb4vQ8Ah/ejMRzcuQXoRRHQrwmJFIeVVZErBPy8twemzzWLnbS2txMIZPg7 XmDgyeaQfeJMCPH6ZVGgFwLqFbff20QEsrh+B8jlBZrCWcSfYj18884dDGGZRdkBZeYH d22xyV6teplmxdso4krP5zzl7OYlYPx59FDEFVOHloj1ZeteS7GIVps/8ArwiojfVyxG wqvw== X-Gm-Message-State: AOAM532VwM3om/PsM3whNs0m8e2fyzjq4RxJ7DcuJ/Tuh9pbs+7Brb5L 5Bym2qhLWERJWJvdUhL7KRtAs1EojoQAlA== X-Google-Smtp-Source: ABdhPJxt3V81G6FwcmRvfduujajJT+UkUWGfb9aE9QXiSeN5vIzx6l9WGQgUPJ3Ixd0lJfdQnIyF2Q== X-Received: by 2002:a17:906:abd4:b0:6bb:8aee:92c5 with SMTP id kq20-20020a170906abd400b006bb8aee92c5mr2226886ejb.660.1645707580348; Thu, 24 Feb 2022 04:59:40 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id a6sm1272785edu.22.2022.02.24.04.59.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Feb 2022 04:59:38 -0800 (PST) From: Daniel Vetter To: DRI Development Subject: [PATCH] drm/todo: Update panic handling todo Date: Thu, 24 Feb 2022 13:59:34 +0100 Message-Id: <20220224125934.3461478-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Vetter , Daniel Vetter , Javier Martinez Canillas , gpiccoli@igalia.com Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Some things changed, and add two useful links. Cc: Javier Martinez Canillas Cc: Pekka Paalanen Cc: gpiccoli@igalia.com Signed-off-by: Daniel Vetter Reviewed-by: Javier Martinez Canillas --- Documentation/gpu/todo.rst | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 7bf7f2111696..283d35a500bd 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -475,8 +475,12 @@ This is a really varied tasks with lots of little bits and pieces: achieved by using an IPI to the local processor. * There's a massive confusion of different panic handlers. DRM fbdev emulation - helpers have one, but on top of that the fbcon code itself also has one. We - need to make sure that they stop fighting over each another. + helpers had their own (long removed), but on top of that the fbcon code itself + also has one. We need to make sure that they stop fighting over each another. + This is worked around by checking ``oops_in_progress`` at various entry points + into the DRM fbdev emulation helpers. A much cleaner approach here would be to + switch fbcon to the `threaded printk support + `_. * ``drm_can_sleep()`` is a mess. It hides real bugs in normal operations and isn't a full solution for panic paths. We need to make sure that it only @@ -488,16 +492,9 @@ This is a really varied tasks with lots of little bits and pieces: even spinlocks (because NMI and hardirq can panic too). We need to either make sure to not call such paths, or trylock everything. Really tricky. -* For the above locking troubles reasons it's pretty much impossible to - attempt a synchronous modeset from panic handlers. The only thing we could - try to achive is an atomic ``set_base`` of the primary plane, and hope that - it shows up. Everything else probably needs to be delayed to some worker or - something else which happens later on. Otherwise it just kills the box - harder, prevent the panic from going out on e.g. netconsole. - -* There's also proposal for a simplied DRM console instead of the full-blown - fbcon and DRM fbdev emulation. Any kind of panic handling tricks should - obviously work for both console, in case we ever get kmslog merged. +* A clean solution would be an entirely separate panic output support in KMS, + bypassing the current fbcon support. See `[PATCH v2 0/3] drm: Add panic handling + `_. Contact: Daniel Vetter