[PATCH v2] drm/amdgpu: Fix the dead lock issue.

[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:
>>         if (!list_empty(&bo->shadow_list)) {
>>                 mutex_lock(&adev->shadow_list_lock);
>>                 list_del_init(&bo->shadow_list);
>>                 mutex_unlock(&adev->shadow_list_lock);
>>         }
>
>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;
>>>>    };
>
>_______________________________________________
>amd-gfx mailing list
>amd-gfx at lists.freedesktop.org
>https://lists.freedesktop.org/mailman/listinfo/amd-gfx