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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55E23C433F5 for ; Tue, 12 Apr 2022 20:03:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233341AbiDLUFg (ORCPT ); Tue, 12 Apr 2022 16:05:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231586AbiDLUFZ (ORCPT ); Tue, 12 Apr 2022 16:05:25 -0400 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB95458E70 for ; Tue, 12 Apr 2022 12:55:57 -0700 (PDT) Received: from [IPV6:2a00:5f00:102:0:10b3:10ff:fe5d:4ec1] (unknown [IPv6:2a00:5f00:102:0:10b3:10ff:fe5d:4ec1]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: dmitry.osipenko) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 618321F448EB; Tue, 12 Apr 2022 20:55:55 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1649793356; bh=8v13VbpDfTPHFcIUff92WA/rM4Ce4zklxdlsVEskFgo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=CpvT/5HWIg6oGGFy5RA4uOZ+HCrNo7pIe8W9MODaa6eFwTR6icCzJMpP7s9/fHeDD iyWQZrpAeHAmtrYDuhIJJpZbG/1v5eCjQYe07/8toQjKO8zIosoZUCF35UZSmoWC8z 1jKMxdozcgfGNL7JxaMqk8mF/7QIpaTuO3D+g/3Muqb+KDrIp+2ov+NWGqpDKYxcIj o++aVl/CSv3Tu8mqQWAQMPN4lh1a2SdJuekJf2E2+XIuISuwJ+7Pa4qx3wERkcGVbF c1Jm4d1qWrlRqxzuPI2LWdExgR9c1KtOuirKx3P4NHBbFHmGyqEhlyainUOHrL7yPQ ypvw/VyITheSA== Message-ID: <3076593e-9ff1-bb73-b05c-000a7a502caa@collabora.com> Date: Tue, 12 Apr 2022 22:55:52 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH v1] drm/scheduler: Don't kill jobs in interrupt context Content-Language: en-US To: Andrey Grodzovsky , David Airlie , Daniel Vetter , Tomeu Vizoso , Steven Price , Rob Herring , Alyssa Rosenzweig , Rob Clark Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Dmitry Osipenko References: <20220411221536.283312-1-dmitry.osipenko@collabora.com> <064d8958-a288-64e1-b2a4-c2302a456d5b@amd.com> From: Dmitry Osipenko In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/12/22 22:40, Andrey Grodzovsky wrote: > > On 2022-04-12 14:20, Dmitry Osipenko wrote: >> On 4/12/22 19:51, Andrey Grodzovsky wrote: >>> On 2022-04-11 18:15, Dmitry Osipenko wrote: >>>> Interrupt context can't sleep. Drivers like Panfrost and MSM are taking >>>> mutex when job is released, and thus, that code can sleep. This results >>>> into "BUG: scheduling while atomic" if locks are contented while job is >>>> freed. There is no good reason for releasing scheduler's jobs in IRQ >>>> context, hence use normal context to fix the trouble. >>> >>> I am not sure this is the beast Idea to leave job's sw fence signalling >>> to be >>> executed in system_wq context which is prone to delays of executing >>> various work items from around the system. Seems better to me to >>> leave the >>> fence signaling within the IRQ context and offload only the job >>> freeing or, >>> maybe handle rescheduling to thread context within drivers implemention >>> of .free_job cb. Not really sure which is the better. >> We're talking here about killing jobs when driver destroys context, >> which doesn't feel like it needs to be a fast path. I could move the >> signalling into drm_sched_entity_kill_jobs_cb() and use unbound wq, but >> do we really need this for a slow path? > > > You can't move the signaling back to drm_sched_entity_kill_jobs_cb > since this will bring back the lockdep splat that 'drm/sched: Avoid > lockdep spalt on killing a processes' > was fixing. Indeed > I see your point and i guess we can go this way too. Another way would > be to add to > panfrost and msm job a  work_item and reschedule to thread context from > within their > .free_job callbacks but that probably to cumbersome to be justified here. Yes, there is no clear justification for doing that. > Andrey > > > Reviewed-by: Andrey Grodzovsky Thank you!