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Reply-To: christian.koenig@amd.com
Subject: Re: [PATCH 0/4] Backported amdgpu ttm deadlock fixes for 4.14
To: Lyude Paul <lyude@redhat.com>, stable@vger.kernel.org
Cc: Chunming Zhou <david1.zhou@amd.com>,
        =?UTF-8?Q?Nicolai_H=c3=a4hnle?= <nicolai.haehnle@amd.com>,
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References: <20171201002311.28098-1-lyude@redhat.com>
From: =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>
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Date: Fri, 1 Dec 2017 09:27:00 +0100
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Am 01.12.2017 um 01:23 schrieb Lyude Paul:
> I haven't gone to see where it started, but as of late a good number of
> pretty nasty deadlock issues have appeared with the kernel. Easy
> reproduction recipe on a laptop with i915/amdgpu prime with lockdep enabled:
>
> DRI_PRIME=1 glxinfo

Acked-by: Christian König <christian.koenig@amd.com>

Thanks for taking care of this,
Christian.

>
> Additionally, some more race conditions exist that I've managed to
> trigger with piglit and lockdep enabled after applying these patches:
>
>      =============================
>      WARNING: suspicious RCU usage
>      4.14.3Lyude-Test+ #2 Not tainted
>      -----------------------------
>      ./include/linux/reservation.h:216 suspicious rcu_dereference_protected() usage!
>
>      other info that might help us debug this:
>
>      rcu_scheduler_active = 2, debug_locks = 1
>      1 lock held by ext_image_dma_b/27451:
>       #0:  (reservation_ww_class_mutex){+.+.}, at: [<ffffffffa034f2ff>] ttm_bo_unref+0x9f/0x3c0 [ttm]
>
>      stack backtrace:
>      CPU: 0 PID: 27451 Comm: ext_image_dma_b Not tainted 4.14.3Lyude-Test+ #2
>      Hardware name: HP HP ZBook 15 G4/8275, BIOS P70 Ver. 01.02 06/09/2017
>      Call Trace:
>       dump_stack+0x8e/0xce
>       lockdep_rcu_suspicious+0xc5/0x100
>       reservation_object_copy_fences+0x292/0x2b0
>       ? ttm_bo_unref+0x9f/0x3c0 [ttm]
>       ttm_bo_unref+0xbd/0x3c0 [ttm]
>       amdgpu_bo_unref+0x2a/0x50 [amdgpu]
>       amdgpu_gem_object_free+0x4b/0x50 [amdgpu]
>       drm_gem_object_free+0x1f/0x40 [drm]
>       drm_gem_object_put_unlocked+0x40/0xb0 [drm]
>       drm_gem_object_handle_put_unlocked+0x6c/0xb0 [drm]
>       drm_gem_object_release_handle+0x51/0x90 [drm]
>       drm_gem_handle_delete+0x5e/0x90 [drm]
>       ? drm_gem_handle_create+0x40/0x40 [drm]
>       drm_gem_close_ioctl+0x20/0x30 [drm]
>       drm_ioctl_kernel+0x5d/0xb0 [drm]
>       drm_ioctl+0x2f7/0x3b0 [drm]
>       ? drm_gem_handle_create+0x40/0x40 [drm]
>       ? trace_hardirqs_on_caller+0xf4/0x190
>       ? trace_hardirqs_on+0xd/0x10
>       amdgpu_drm_ioctl+0x4f/0x90 [amdgpu]
>       do_vfs_ioctl+0x93/0x670
>       ? __fget+0x108/0x1f0
>       SyS_ioctl+0x79/0x90
>       entry_SYSCALL_64_fastpath+0x23/0xc2
>
> I've also added the relevant fixes for the issue mentioned above.
>
> Christian König (3):
>    drm/ttm: fix ttm_bo_cleanup_refs_or_queue once more
>    dma-buf: make reservation_object_copy_fences rcu save
>    drm/amdgpu: reserve root PD while releasing it
>
> Michel Dänzer (1):
>    drm/ttm: Always and only destroy bo->ttm_resv in ttm_bo_release_list
>
>   drivers/dma-buf/reservation.c          | 56 +++++++++++++++++++++++++---------
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 13 ++++++--
>   drivers/gpu/drm/ttm/ttm_bo.c           | 43 +++++++++++++-------------
>   3 files changed, 74 insertions(+), 38 deletions(-)
>
> --
> 2.14.3
>
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