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Date:   Tue, 12 May 2020 14:58:41 +0200
From:   Daniel Vetter <daniel@ffwll.ch>
To:     Alex Deucher <alexdeucher@gmail.com>
Cc:     Daniel Vetter <daniel.vetter@ffwll.ch>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        linux-rdma@vger.kernel.org,
        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@lists.linaro.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        linux-media <linux-media@vger.kernel.org>
Subject: Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets
Message-ID: <20200512125841.GH206103@phenom.ffwll.local>
Mail-Followup-To: Alex Deucher <alexdeucher@gmail.com>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        linux-rdma@vger.kernel.org,
        Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        amd-gfx list <amd-gfx@lists.freedesktop.org>,
        Chris Wilson <chris@chris-wilson.co.uk>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" <linaro-mm-sig@lists.linaro.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        linux-media <linux-media@vger.kernel.org>
References: <20200512085944.222637-1-daniel.vetter@ffwll.ch>
 <20200512085944.222637-17-daniel.vetter@ffwll.ch>
 <CADnq5_NJTwkUszd-F2d4D+kD4c_+FKD8tuhVJ7VWHGxAyd8fCg@mail.gmail.com>
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On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > ...
> >
> > I think it's time to stop this little exercise.
> >
> > The lockdep splat, for the record:
> >
> > [  132.583381] ======================================================
> > [  132.584091] WARNING: possible circular locking dependency detected
> > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > [  132.585461] ------------------------------------------------------
> > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.587569]
> >                but task is already holding lock:
> > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > [  132.589803]
> >                which lock already depends on the new lock.
> >
> > [  132.592009]
> >                the existing dependency chain (in reverse order) is:
> > [  132.593507]
> >                -> #2 (dma_fence_map){++++}-{0:0}:
> > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > [  132.600539]        fbcon_init+0x2e8/0x660
> > [  132.601344]        visual_init+0xce/0x130
> > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > [  132.602970]        do_take_over_console+0x115/0x180
> > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > [  132.604564]        register_framebuffer+0x1ee/0x300
> > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > [  132.609511]        local_pci_probe+0x42/0x80
> > [  132.610324]        pci_device_probe+0x104/0x1a0
> > [  132.611130]        really_probe+0x147/0x3c0
> > [  132.611939]        driver_probe_device+0xb6/0x100
> > [  132.612766]        device_driver_attach+0x53/0x60
> > [  132.613593]        __driver_attach+0x8c/0x150
> > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > [  132.616071]        driver_register+0x6c/0xc0
> > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > [  132.617731]        do_init_module+0x5c/0x230
> > [  132.618560]        load_module+0x2981/0x2bc0
> > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > [  132.620228]        do_syscall_64+0x5a/0x250
> > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > [  132.621903]
> >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > [  132.629804]        local_pci_probe+0x42/0x80
> > [  132.630690]        pci_device_probe+0x104/0x1a0
> > [  132.631583]        really_probe+0x147/0x3c0
> > [  132.632479]        driver_probe_device+0xb6/0x100
> > [  132.633379]        device_driver_attach+0x53/0x60
> > [  132.634275]        __driver_attach+0x8c/0x150
> > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > [  132.636974]        driver_register+0x6c/0xc0
> > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > [  132.638765]        do_init_module+0x5c/0x230
> > [  132.639654]        load_module+0x2981/0x2bc0
> > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > [  132.641372]        do_syscall_64+0x5a/0x250
> > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > [  132.643022]
> >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > [  132.645469]        lock_acquire+0xad/0x370
> > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > [  132.652594]        process_one_work+0x23c/0x580
> > [  132.653402]        worker_thread+0x50/0x3b0
> > [  132.654139]        kthread+0x12e/0x150
> > [  132.654868]        ret_from_fork+0x27/0x50
> > [  132.655598]
> >                other info that might help us debug this:
> >
> > [  132.657739] Chain exists of:
> >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> >
> > [  132.659877]  Possible unsafe locking scenario:
> >
> > [  132.661416]        CPU0                    CPU1
> > [  132.662126]        ----                    ----
> > [  132.662847]   lock(dma_fence_map);
> > [  132.663574]                                lock(crtc_ww_class_mutex);
> > [  132.664319]                                lock(dma_fence_map);
> > [  132.665063]   lock(crtc_ww_class_acquire);
> > [  132.665799]
> >                 *** DEADLOCK ***
> >
> > [  132.667965] 4 locks held by kworker/2:3/865:
> > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > [  132.671902]
> >                stack backtrace:
> > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > [  132.676046] Call Trace:
> > [  132.676897]  dump_stack+0x8f/0xd0
> > [  132.677748]  check_noncircular+0x162/0x180
> > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > [  132.680311]  lock_acquire+0xad/0x370
> > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.682021]  ? cpumask_next+0x16/0x20
> > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > [  132.683737]  ? __module_address+0x28/0xf0
> > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > [  132.693597]  process_one_work+0x23c/0x580
> > [  132.694487]  worker_thread+0x50/0x3b0
> > [  132.695373]  ? process_one_work+0x580/0x580
> > [  132.696264]  kthread+0x12e/0x150
> > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > [  132.698057]  ret_from_fork+0x27/0x50
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian K?nig <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > index 3584e29323c0..b3b84a0d3baf 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> >                 /* displays are handled separately */
> >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> >                         /* XXX handle errors */
> > +
> > +                       /*
> > +                        * This is dm_suspend, which calls modeset locks, and
> > +                        * that a pretty good inversion against dma_fence_signal
> > +                        * which gpu recovery is supposed to guarantee.
> > +                        *
> > +                        * Dont ask me how to fix this.
> > +                        */
> 
> We actually have a fix for this.  Will be out shortly.

Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
the display block entirely. Fixing the locking while still resetting the
display is going to be really hard otoh ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch