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Message-ID: <38c166f4-3eb1-76f2-8db5-5783ef9f1650@ti.com>
Date:   Tue, 3 Oct 2023 05:48:51 +0530
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Subject: Re: [PATCH 1/2] Revert "drm/tidss: 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>,
        Devarsh Thakkar <devarsht@ti.com>,
        Jai Luthra <j-luthra@ti.com>,
        Jayesh Choudhary <j-choudhary@ti.com>
References: <20230920-dma-fence-annotation-revert-v1-0-7ebf6f7f5bf6@ideasonboard.com>
 <20230920-dma-fence-annotation-revert-v1-1-7ebf6f7f5bf6@ideasonboard.com>
From:   Aradhya Bhatia <a-bhatia1@ti.com>
In-Reply-To: <20230920-dma-fence-annotation-revert-v1-1-7ebf6f7f5bf6@ideasonboard.com>
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On 20-Sep-23 18:27, Tomi Valkeinen wrote:
> This reverts commit 4d56a4f08391857ba93465de489707b66adad114.
> 
> 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
> 6.6.0-rc2+ #1 Not tainted
> ------------------------------------------------------
> kmstest/733 is trying to acquire lock:
> ffff8000819377f0 (fs_reclaim){+.+.}-{0:0}, at: __kmem_cache_alloc_node+0x58/0x2d4
> 
> but task is already holding lock:
> ffff800081a06aa0 (dma_fence_map){++++}-{0:0}, at: tidss_atomic_commit_tail+0x20/0xc0 [tidss]
> 
> 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+0x5c/0xd0
>        dma_resv_lockdep+0x1a4/0x32c
>        do_one_initcall+0x84/0x2fc
>        kernel_init_freeable+0x28c/0x4c4
>        kernel_init+0x24/0x1dc
>        ret_from_fork+0x10/0x20
> 
> -> #1 (mmu_notifier_invalidate_range_start){+.+.}-{0:0}:
>        fs_reclaim_acquire+0x70/0xe4
>        __kmem_cache_alloc_node+0x58/0x2d4
>        kmalloc_trace+0x38/0x78
>        __kthread_create_worker+0x3c/0x150
>        kthread_create_worker+0x64/0x8c
>        workqueue_init+0x1e8/0x2f0
>        kernel_init_freeable+0x11c/0x4c4
>        kernel_init+0x24/0x1dc
>        ret_from_fork+0x10/0x20
> 
> -> #0 (fs_reclaim){+.+.}-{0:0}:
>        __lock_acquire+0x1370/0x20d8
>        lock_acquire+0x1e8/0x308
>        fs_reclaim_acquire+0xd0/0xe4
>        __kmem_cache_alloc_node+0x58/0x2d4
>        __kmalloc_node_track_caller+0x58/0xf0
>        kmemdup+0x34/0x60
>        regmap_bulk_write+0x64/0x2c0
>        tc358768_bridge_pre_enable+0x8c/0x12d0 [tc358768]
>        drm_atomic_bridge_call_pre_enable+0x68/0x80 [drm]
>        drm_atomic_bridge_chain_pre_enable+0x50/0x158 [drm]
>        drm_atomic_helper_commit_modeset_enables+0x164/0x264 [drm_kms_helper]
>        tidss_atomic_commit_tail+0x58/0xc0 [tidss]
>        commit_tail+0xa0/0x188 [drm_kms_helper]
>        drm_atomic_helper_commit+0x1a8/0x1c0 [drm_kms_helper]
>        drm_atomic_commit+0xa8/0xe0 [drm]
>        drm_mode_atomic_ioctl+0x9ec/0xc80 [drm]
>        drm_ioctl_kernel+0xc4/0x170 [drm]
>        drm_ioctl+0x234/0x4b0 [drm]
>        drm_compat_ioctl+0x110/0x12c [drm]
>        __arm64_compat_sys_ioctl+0x128/0x150
>        invoke_syscall+0x48/0x110
>        el0_svc_common.constprop.0+0x40/0xe0
>        do_el0_svc_compat+0x1c/0x38
>        el0_svc_compat+0x48/0xb4
>        el0t_32_sync_handler+0xb0/0x138
>        el0t_32_sync+0x194/0x198
> 
> other info that might help us debug this:
> 
> Chain exists of:
>   fs_reclaim --> mmu_notifier_invalidate_range_start --> dma_fence_map
> 
>  Possible unsafe locking scenario:
> 
>        CPU0                    CPU1
>        ----                    ----
>   rlock(dma_fence_map);
>                                lock(mmu_notifier_invalidate_range_start);
>                                lock(dma_fence_map);
>   lock(fs_reclaim);
> 
>  *** DEADLOCK ***
> 
> 3 locks held by kmstest/733:
>  #0: ffff800082e5bba0 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_mode_atomic_ioctl+0x118/0xc80 [drm]
>  #1: ffff000004224c88 (crtc_ww_class_mutex){+.+.}-{3:3}, at: modeset_lock+0xdc/0x1a0 [drm]
>  #2: ffff800081a06aa0 (dma_fence_map){++++}-{0:0}, at: tidss_atomic_commit_tail+0x20/0xc0 [tidss]
> 
> stack backtrace:
> CPU: 0 PID: 733 Comm: kmstest Not tainted 6.6.0-rc2+ #1
> Hardware name: Toradex Verdin AM62 on Verdin Development Board (DT)
> Call trace:
>  dump_backtrace+0x98/0x118
>  show_stack+0x18/0x24
>  dump_stack_lvl+0x60/0xac
>  dump_stack+0x18/0x24
>  print_circular_bug+0x288/0x368
>  check_noncircular+0x168/0x17c
>  __lock_acquire+0x1370/0x20d8
>  lock_acquire+0x1e8/0x308
>  fs_reclaim_acquire+0xd0/0xe4
>  __kmem_cache_alloc_node+0x58/0x2d4
>  __kmalloc_node_track_caller+0x58/0xf0
>  kmemdup+0x34/0x60
>  regmap_bulk_write+0x64/0x2c0
>  tc358768_bridge_pre_enable+0x8c/0x12d0 [tc358768]
>  drm_atomic_bridge_call_pre_enable+0x68/0x80 [drm]
>  drm_atomic_bridge_chain_pre_enable+0x50/0x158 [drm]
>  drm_atomic_helper_commit_modeset_enables+0x164/0x264 [drm_kms_helper]
>  tidss_atomic_commit_tail+0x58/0xc0 [tidss]
>  commit_tail+0xa0/0x188 [drm_kms_helper]
>  drm_atomic_helper_commit+0x1a8/0x1c0 [drm_kms_helper]
>  drm_atomic_commit+0xa8/0xe0 [drm]
>  drm_mode_atomic_ioctl+0x9ec/0xc80 [drm]
>  drm_ioctl_kernel+0xc4/0x170 [drm]
>  drm_ioctl+0x234/0x4b0 [drm]
>  drm_compat_ioctl+0x110/0x12c [drm]
>  __arm64_compat_sys_ioctl+0x128/0x150
>  invoke_syscall+0x48/0x110
>  el0_svc_common.constprop.0+0x40/0xe0
>  do_el0_svc_compat+0x1c/0x38
>  el0_svc_compat+0x48/0xb4
>  el0t_32_sync_handler+0xb0/0x138
>  el0t_32_sync+0x194/0x198
> 
> Fixes: 4d56a4f08391 ("drm/tidss: 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/tidss/tidss_kms.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_kms.c b/drivers/gpu/drm/tidss/tidss_kms.c
> index c979ad1af236..d096d8d2bc8f 100644
> --- a/drivers/gpu/drm/tidss/tidss_kms.c
> +++ b/drivers/gpu/drm/tidss/tidss_kms.c
> @@ -4,8 +4,6 @@
>   * Author: Tomi Valkeinen <tomi.valkeinen@ti.com>
>   */
>  
> -#include <linux/dma-fence.h>
> -
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_bridge.h>
> @@ -25,7 +23,6 @@ static void tidss_atomic_commit_tail(struct drm_atomic_state *old_state)
>  {
>  	struct drm_device *ddev = old_state->dev;
>  	struct tidss_device *tidss = to_tidss(ddev);
> -	bool fence_cookie = dma_fence_begin_signalling();
>  
>  	dev_dbg(ddev->dev, "%s\n", __func__);
>  
> @@ -36,7 +33,6 @@ static void tidss_atomic_commit_tail(struct drm_atomic_state *old_state)
>  	drm_atomic_helper_commit_modeset_enables(ddev, old_state);
>  
>  	drm_atomic_helper_commit_hw_done(old_state);
> -	dma_fence_end_signalling(fence_cookie);
>  	drm_atomic_helper_wait_for_flip_done(ddev, old_state);
>  
>  	drm_atomic_helper_cleanup_planes(ddev, old_state);
>