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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 43770C47404 for ; Fri, 4 Oct 2019 15:27:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22BFE2133F for ; Fri, 4 Oct 2019 15:27:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389689AbfJDP1m (ORCPT ); Fri, 4 Oct 2019 11:27:42 -0400 Received: from foss.arm.com ([217.140.110.172]:48300 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389210AbfJDP1m (ORCPT ); Fri, 4 Oct 2019 11:27:42 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 345CB1597; Fri, 4 Oct 2019 08:27:41 -0700 (PDT) Received: from [10.1.196.133] (e112269-lin.cambridge.arm.com [10.1.196.133]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E854B3F68E; Fri, 4 Oct 2019 08:27:39 -0700 (PDT) Subject: Re: drm_sched with panfrost crash on T820 To: Neil Armstrong , "Grodzovsky, Andrey" , Hillf Danton Cc: Tomeu Vizoso , "airlied@linux.ie" , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "open list:ARM/Amlogic Meson..." , "Koenig, Christian" , Erico Nunes References: <20190930145228.14000-1-hdanton@sina.com> <7339b7a1-2d1c-4379-89a0-daf8b28d81c8@baylibre.com> <94096e4e-0f60-79d1-69b5-c7c3e59a4d78@amd.com> From: Steven Price Message-ID: <8c4ecad8-c2e2-eec1-9132-48e126577baa@arm.com> Date: Fri, 4 Oct 2019 16:27:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/10/2019 16:03, Neil Armstrong wrote: > On 04/10/2019 16:53, Grodzovsky, Andrey wrote: >> >> On 10/3/19 4:34 AM, Neil Armstrong wrote: >>> Hi Andrey, >>> >>> Le 02/10/2019 à 16:40, Grodzovsky, Andrey a écrit : >>>> On 9/30/19 10:52 AM, Hillf Danton wrote: >>>>> On Mon, 30 Sep 2019 11:17:45 +0200 Neil Armstrong wrote: >>>>>> Did a new run from 5.3: >>>>>> >>>>>> [ 35.971972] Call trace: >>>>>> [ 35.974391] drm_sched_increase_karma+0x5c/0xf0 >>>>>> ffff000010667f38 FFFF000010667F94 >>>>>> drivers/gpu/drm/scheduler/sched_main.c:335 >>>>>> >>>>>> The crashing line is : >>>>>> if (bad->s_fence->scheduled.context == >>>>>> entity->fence_context) { >>>>>> >>>>>> Doesn't seem related to guilty job. >>>>> Bail out if s_fence is no longer fresh. >>>>> >>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c >>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c >>>>> @@ -333,6 +333,10 @@ void drm_sched_increase_karma(struct drm >>>>> >>>>> spin_lock(&rq->lock); >>>>> list_for_each_entry_safe(entity, tmp, &rq->entities, list) { >>>>> + if (!smp_load_acquire(&bad->s_fence)) { >>>>> + spin_unlock(&rq->lock); >>>>> + return; >>>>> + } >>>>> if (bad->s_fence->scheduled.context == >>>>> entity->fence_context) { >>>>> if (atomic_read(&bad->karma) > >>>>> @@ -543,7 +547,7 @@ EXPORT_SYMBOL(drm_sched_job_init); >>>>> void drm_sched_job_cleanup(struct drm_sched_job *job) >>>>> { >>>>> dma_fence_put(&job->s_fence->finished); >>>>> - job->s_fence = NULL; >>>>> + smp_store_release(&job->s_fence, 0); >>>>> } >>>>> EXPORT_SYMBOL(drm_sched_job_cleanup); >>> This fixed the problem on the 10 CI runs. >>> >>> Neil >> >> >> These are good news but I still fail to see how this fixes the problem - >> Hillf, do you mind explaining how you came up with this particular fix - >> what was the bug you saw ? > > As Steven explained, seems the same job was submitted on both HW slots, > and then when timeout occurs each thread calls panfrost_job_timedout > which leads to drm_sched_stop() on the first call and on the > second call the job was already freed. > > Steven proposed a working fix, and this one does the same but on > the drm_sched side. This one looks cleaner, but panfrost should > not call drm_sched_stop() twice for the same job. I'm not sure that Hillf's fix is sufficient. In particular in drm_sched_increase_karma() I don't understand how the smp_load_acquire() call prevents bad->s_fence becoming NULL immediately afterwards (but admittedly the window is much smaller). But really this is just a Panfrost bug (calling drm_sched_stop() twice on the same job). The part of my change that I'd welcome feedback on is changing cancel_delayed_work() to cancel_delayed_work_sync() in drm_sched_stop() when called on different scheduler to the bad job. It's not clear to me exactly what the semantics of the function should be, and I haven't tested the effect of the change on drivers other than Panfrost. Steve > Neil > >> >> Andrey >> >>> >>>> Does this change help the problem ? Note that drm_sched_job_cleanup is >>>> called from scheduler thread which is stopped at all times when work_tdr >>>> thread is running and anyway the 'bad' job is still in the >>>> ring_mirror_list while it's being accessed from >>>> drm_sched_increase_karma so I don't think drm_sched_job_cleanup can be >>>> called for it BEFORE or while drm_sched_increase_karma is executed. >>>> >>>> Andrey >>>> >>>> >>>>> >>>>> -- >>>>> > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel >