Am 10.09.2018 um 11:55 schrieb Deng, Emily:
>> -----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.
That will still go to adev->shadow_list and not affect our local list in
any way.
We are not interested in any newly allocated shadow BOs, so that should
be unproblematic.
Regards,
Christian.
>> 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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