>-----Original Message-----
>From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
>Christian König
>Sent: Monday, September 10, 2018 5:49 PM
>To: Deng, Emily <Emily.Deng at amd.com>; amd-gfx at lists.freedesktop.org
>Subject: Re: [PATCH v2] drm/amdgpu: Fix the dead lock issue.
>
>Am 10.09.2018 um 11:47 schrieb Deng, Emily:
>>> -----Original Message-----
>>> From: Christian König <ckoenig.leichtzumerken at gmail.com>
>>> Sent: Monday, September 10, 2018 5:41 PM
>>> To: Deng, Emily <Emily.Deng at amd.com>; amd-gfx at lists.freedesktop.org
>>> Subject: Re: [PATCH v2] drm/amdgpu: Fix the dead lock issue.
>>>
>>> Am 10.09.2018 um 11:34 schrieb Emily Deng:
>>>> It will ramdomly have the dead lock issue when test TDR:
>>>> 1. amdgpu_device_handle_vram_lost gets the lock shadow_list_lock 2.
>>>> amdgpu_bo_create locked the bo's resv lock 3.
>>>> amdgpu_bo_create_shadow is waiting for the shadow_list_lock 4.
>>>> amdgpu_device_recover_vram_from_shadow is waiting for the bo's resv
>>>> lock.
>>>>
>>>> v2:
>>>> Make a local copy of the list
>>>>
>>>> Signed-off-by: Emily Deng <Emily.Deng at amd.com>
>>>> ---
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 12 +++++++++++-
>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_object.h | 1 +
>>>> 2 files changed, 12 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> index acfc63e..2b9f597 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> @@ -3006,6 +3006,9 @@ static int
>>> amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
>>>> long r = 1;
>>>> int i = 0;
>>>> long tmo;
>>>> + struct list_head local_shadow_list;
>>>> +
>>>> + INIT_LIST_HEAD(&local_shadow_list);
>>>>
>>>> if (amdgpu_sriov_runtime(adev))
>>>> tmo = msecs_to_jiffies(8000);
>>>> @@ -3013,8 +3016,15 @@ static int
>>> amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
>>>> tmo = msecs_to_jiffies(100);
>>>>
>>>> DRM_INFO("recover vram bo from shadow start\n");
>>>> +
>>>> mutex_lock(&adev->shadow_list_lock);
>>>> list_for_each_entry_safe(bo, tmp, &adev->shadow_list,
>>>> shadow_list) {
>>>> + amdgpu_bo_ref(bo);
>>>> + list_add_tail(&bo->copy_shadow_list, &local_shadow_list);
>>>> + }
>>> Please don't add an extra copy_shadow_list field to amdgpu_bo.
>> If don't use an extra variable, the local shadow list will change
>> according the adev->shadow_list, both for adding or deleting, it is not we
>want.
>
>That is not correct, see amdgpu_bo_destroy:
>> Â Â Â Â Â Â Â if (!list_empty(&bo->shadow_list)) {
>> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â mutex_lock(&adev->shadow_list_lock);
>> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â list_del_init(&bo->shadow_list);
>> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â mutex_unlock(&adev->shadow_list_lock);
>> Â Â Â Â Â Â Â }
>
>The BO is only removed from the list when it is destroyed, since we grabbed a
>local reference it can't be destroyed. So we are safe here.
Sorry I am not meaning the delete, what about the adding.
>Regards,
>Christian.
>
>>
>>> Instead just use bo->shadow list for this. When you hold a reference
>>> to the BO it should not be removed from the shadow list.
>>>
>>> Additional to that you can just use list_splice_init() to move the
>>> whole shadow list to your local list.
>>>
>>> Christian.
>>>
>>>> + mutex_unlock(&adev->shadow_list_lock);
>>>> +
>>>> + list_for_each_entry_safe(bo, tmp, &local_shadow_list,
>>>> +copy_shadow_list) {
>>>> next = NULL;
>>>> amdgpu_device_recover_vram_from_shadow(adev, ring, bo,
>>> &next);
>>>> if (fence) {
>>>> @@ -3033,8 +3043,8 @@ static int
>>> amdgpu_device_handle_vram_lost(struct
>>>> amdgpu_device *adev)
>>>>
>>>> dma_fence_put(fence);
>>>> fence = next;
>>>> + amdgpu_bo_unref(&bo);
>>>> }
>>>> - mutex_unlock(&adev->shadow_list_lock);
>>>>
>>>> if (fence) {
>>>> r = dma_fence_wait_timeout(fence, false, tmo); diff --git
>>>> a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> index 907fdf4..cfee16c 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.h
>>>> @@ -103,6 +103,7 @@ struct amdgpu_bo {
>>>> struct list_head mn_list;
>>>> struct list_head shadow_list;
>>>> };
>>>> + struct list_head copy_shadow_list;
>>>>
>>>> struct kgd_mem *kfd_bo;
>>>> };
>
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