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 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 1E2EFCCFA05 for ; Fri, 7 Nov 2025 13:57:27 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8A7A210EACE; Fri, 7 Nov 2025 13:57:26 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="trWAvWOR"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 5B72F10EACE for ; Fri, 7 Nov 2025 13:57:25 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 3CEFD446BA; Fri, 7 Nov 2025 13:57:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C81A4C4CEF8; Fri, 7 Nov 2025 13:57:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762523845; bh=Z8U/akBsldXiiAXmfTRDia6T57dNa1mxa22yotGMNtI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=trWAvWOR9eqC8BxkMy6CDLWzGBj9gNBPrMD7XJW4DAu65A0bEzxzvNY3EDq5j8Slc PZ5pg6Nfr11YJHQCZ+JyMWzIBMQs1kYHApIl+vkSCyIF6PHTJPcQY4lwLx8T91eBpI oDElKg2AylMW4SeZoCAvcgiKAVNFL7S1g0575a71DMsVaP0J+KhGcg8cmahb2WUbgS DsMWTd8lPy2KzJalhXpaf8IO9ncfkHQZYiVC6XGULKyLGeyL+IH9LhnQ6fkKX832Jt pQ3HwVqztpAVOUlqbw9zganTTSxsQRpk+WC8RwtKGBpji1yYlZnXhBfqBpuKZ4xC+m 43YAwYv1ungnQ== From: Philipp Stanner To: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jonathan Corbet Cc: dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Philipp Stanner Subject: [PATCH v2 2/2] drm/todo: Add entry for unlocked drm/sched rq readers Date: Fri, 7 Nov 2025 14:57:01 +0100 Message-ID: <20251107135701.244659-4-phasta@kernel.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20251107135701.244659-2-phasta@kernel.org> References: <20251107135701.244659-2-phasta@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Runqueues are currently almost everywhere being read unlocked in drm/sched. At XDC 2025, the assembled developers were unsure whether that's legal and whether it can be fixed. Someone should find out. Add a todo entry for the unlocked runqueue reader problem. Signed-off-by: Philipp Stanner --- Documentation/gpu/todo.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 084e148e78c1..fc8bafd593d8 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -909,6 +909,20 @@ Contact: Christian König Level: Advanced +Add locking for runqueues +------------------------- + +There is an old FIXME by Sima in include/drm/gpu_scheduler.h. It details that +struct drm_sched_rq is read at many places without any locks, not even with a +READ_ONCE. At XDC 2025 no one could really tell why that is the case, whether +locks are needed and whether they could be added. (But for real, that should +probably be locked!). Check whether it's possible to add locks everywhere, and +do so if yes. + +Contact: Philipp Stanner + +Level: Intermediate + Outside DRM =========== -- 2.49.0