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Message-ID: <484f6dd2-ed17-16af-0e1e-0ae6926eec53@ti.com>
Date:   Tue, 3 Oct 2023 10:55:20 +0530
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Subject: Re: [PATCH 2/2] Revert "drm/omapdrm: Annotate dma-fence critical
 section in commit path"
Content-Language: en-US
To:     Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
        Daniel Vetter <daniel@ffwll.ch>
CC:     Jyri Sarha <jyri.sarha@iki.fi>, David Airlie <airlied@gmail.com>,
        <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        Francesco Dolcini <francesco@dolcini.it>
References: <20230920-dma-fence-annotation-revert-v1-0-7ebf6f7f5bf6@ideasonboard.com>
 <20230920-dma-fence-annotation-revert-v1-2-7ebf6f7f5bf6@ideasonboard.com>
From:   Aradhya Bhatia <a-bhatia1@ti.com>
In-Reply-To: <20230920-dma-fence-annotation-revert-v1-2-7ebf6f7f5bf6@ideasonboard.com>
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On 20-Sep-23 18:27, Tomi Valkeinen wrote:
> This reverts commit 250aa22920cd5d956a5d3e9c6a43d671c2bae217.
> 
> The DMA-fence annotations cause a lockdep warning (see below). As per
> https://patchwork.freedesktop.org/patch/462170/ it sounds like the
> annotations don't work correctly.
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 6.5.0-rc2+ #2 Not tainted
> ------------------------------------------------------
> kmstest/219 is trying to acquire lock:
> c4705838 (&hdmi->lock){+.+.}-{3:3}, at: hdmi5_bridge_mode_set+0x1c/0x50
> 
> but task is already holding lock:
> c11e1128 (dma_fence_map){++++}-{0:0}, at: omap_atomic_commit_tail+0x14/0xbc
> 
> which lock already depends on the new lock.
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #2 (dma_fence_map){++++}-{0:0}:
>        __dma_fence_might_wait+0x48/0xb4
>        dma_resv_lockdep+0x1b8/0x2bc
>        do_one_initcall+0x68/0x3b0
>        kernel_init_freeable+0x260/0x34c
>        kernel_init+0x14/0x140
>        ret_from_fork+0x14/0x28
> 
> -> #1 (fs_reclaim){+.+.}-{0:0}:
>        fs_reclaim_acquire+0x70/0xa8
>        __kmem_cache_alloc_node+0x3c/0x368
>        kmalloc_trace+0x28/0x58
>        _drm_do_get_edid+0x7c/0x35c
>        hdmi5_bridge_get_edid+0xc8/0x1ac
>        drm_bridge_connector_get_modes+0x64/0xc0
>        drm_helper_probe_single_connector_modes+0x170/0x528
>        drm_client_modeset_probe+0x208/0x1334
>        __drm_fb_helper_initial_config_and_unlock+0x30/0x548
>        omap_fbdev_client_hotplug+0x3c/0x6c
>        drm_client_register+0x58/0x94
>        pdev_probe+0x544/0x6b0
>        platform_probe+0x58/0xbc
>        really_probe+0xd8/0x3fc
>        __driver_probe_device+0x94/0x1f4
>        driver_probe_device+0x2c/0xc4
>        __device_attach_driver+0xa4/0x11c
>        bus_for_each_drv+0x84/0xdc
>        __device_attach+0xac/0x20c
>        bus_probe_device+0x8c/0x90
>        device_add+0x588/0x7e0
>        platform_device_add+0x110/0x24c
>        platform_device_register_full+0x108/0x15c
>        dss_bind+0x90/0xc0
>        try_to_bring_up_aggregate_device+0x1e0/0x2c8
>        __component_add+0xa4/0x174
>        hdmi5_probe+0x1c8/0x270
>        platform_probe+0x58/0xbc
>        really_probe+0xd8/0x3fc
>        __driver_probe_device+0x94/0x1f4
>        driver_probe_device+0x2c/0xc4
>        __device_attach_driver+0xa4/0x11c
>        bus_for_each_drv+0x84/0xdc
>        __device_attach+0xac/0x20c
>        bus_probe_device+0x8c/0x90
>        deferred_probe_work_func+0x8c/0xd8
>        process_one_work+0x2ac/0x6e4
>        worker_thread+0x30/0x4ec
>        kthread+0x100/0x124
>        ret_from_fork+0x14/0x28
> 
> -> #0 (&hdmi->lock){+.+.}-{3:3}:
>        __lock_acquire+0x145c/0x29cc
>        lock_acquire.part.0+0xb4/0x258
>        __mutex_lock+0x90/0x950
>        mutex_lock_nested+0x1c/0x24
>        hdmi5_bridge_mode_set+0x1c/0x50
>        drm_bridge_chain_mode_set+0x48/0x5c
>        crtc_set_mode+0x188/0x1d0
>        omap_atomic_commit_tail+0x2c/0xbc
>        commit_tail+0x9c/0x188
>        drm_atomic_helper_commit+0x158/0x18c
>        drm_atomic_commit+0xa4/0xe8
>        drm_mode_atomic_ioctl+0x9a4/0xc38
>        drm_ioctl+0x210/0x4a8
>        sys_ioctl+0x138/0xf00
>        ret_fast_syscall+0x0/0x1c
> 
> other info that might help us debug this:
> 
> Chain exists of:
>   &hdmi->lock --> fs_reclaim --> dma_fence_map
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   rlock(dma_fence_map);
>                                lock(fs_reclaim);
>                                lock(dma_fence_map);
>   lock(&hdmi->lock);
> 
>  *** DEADLOCK ***
> 
> 3 locks held by kmstest/219:
>  #0: f1011de4 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_mode_atomic_ioctl+0xf0/0xc38
>  #1: c47059c8 (crtc_ww_class_mutex){+.+.}-{3:3}, at: modeset_lock+0xf8/0x230
>  #2: c11e1128 (dma_fence_map){++++}-{0:0}, at: omap_atomic_commit_tail+0x14/0xbc
> 
> stack backtrace:
> CPU: 1 PID: 219 Comm: kmstest Not tainted 6.5.0-rc2+ #2
> Hardware name: Generic DRA74X (Flattened Device Tree)
>  unwind_backtrace from show_stack+0x10/0x14
>  show_stack from dump_stack_lvl+0x58/0x70
>  dump_stack_lvl from check_noncircular+0x164/0x198
>  check_noncircular from __lock_acquire+0x145c/0x29cc
>  __lock_acquire from lock_acquire.part.0+0xb4/0x258
>  lock_acquire.part.0 from __mutex_lock+0x90/0x950
>  __mutex_lock from mutex_lock_nested+0x1c/0x24
>  mutex_lock_nested from hdmi5_bridge_mode_set+0x1c/0x50
>  hdmi5_bridge_mode_set from drm_bridge_chain_mode_set+0x48/0x5c
>  drm_bridge_chain_mode_set from crtc_set_mode+0x188/0x1d0
>  crtc_set_mode from omap_atomic_commit_tail+0x2c/0xbc
>  omap_atomic_commit_tail from commit_tail+0x9c/0x188
>  commit_tail from drm_atomic_helper_commit+0x158/0x18c
>  drm_atomic_helper_commit from drm_atomic_commit+0xa4/0xe8
>  drm_atomic_commit from drm_mode_atomic_ioctl+0x9a4/0xc38
>  drm_mode_atomic_ioctl from drm_ioctl+0x210/0x4a8
>  drm_ioctl from sys_ioctl+0x138/0xf00
>  sys_ioctl from ret_fast_syscall+0x0/0x1c
> Exception stack(0xf1011fa8 to 0xf1011ff0)
> 1fa0:                   00466d58 be9ab510 00000003 c03864bc be9ab510 be9ab4e0
> 1fc0: 00466d58 be9ab510 c03864bc 00000036 00466ef0 00466fc0 00467020 00466f20
> 1fe0: b6bc7ef4 be9ab4d0 b6bbbb00 b6cb2cc0
> 
> Fixes: 250aa22920cd ("drm/omapdrm: Annotate dma-fence critical section in commit path")
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---

Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>

Regards
Aradhya

>  drivers/gpu/drm/omapdrm/omap_drv.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> index afeeb7737552..e000577a95dd 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> @@ -69,7 +69,6 @@ static void omap_atomic_commit_tail(struct drm_atomic_state *old_state)
>  {
>  	struct drm_device *dev = old_state->dev;
>  	struct omap_drm_private *priv = dev->dev_private;
> -	bool fence_cookie = dma_fence_begin_signalling();
>  
>  	dispc_runtime_get(priv->dispc);
>  
> @@ -92,6 +91,8 @@ static void omap_atomic_commit_tail(struct drm_atomic_state *old_state)
>  		omap_atomic_wait_for_completion(dev, old_state);
>  
>  		drm_atomic_helper_commit_planes(dev, old_state, 0);
> +
> +		drm_atomic_helper_commit_hw_done(old_state);
>  	} else {
>  		/*
>  		 * OMAP3 DSS seems to have issues with the work-around above,
> @@ -101,11 +102,9 @@ static void omap_atomic_commit_tail(struct drm_atomic_state *old_state)
>  		drm_atomic_helper_commit_planes(dev, old_state, 0);
>  
>  		drm_atomic_helper_commit_modeset_enables(dev, old_state);
> -	}
>  
> -	drm_atomic_helper_commit_hw_done(old_state);
> -
> -	dma_fence_end_signalling(fence_cookie);
> +		drm_atomic_helper_commit_hw_done(old_state);
> +	}
>  
>  	/*
>  	 * Wait for completion of the page flips to ensure that old buffers
>