Re: [PATCH 11/20] drm/amdgpu: fix KFD eviction fence enable_signaling path

["Kuehling, Felix" <felix.kuehling@amd.com>]

On 2025-11-06 08:43, Christian König wrote:
> On 11/4/25 17:28, Philipp Stanner wrote:
>> On Fri, 2025-10-31 at 14:16 +0100, Christian König wrote:
>>> Calling dma_fence_is_signaled() here is illegal!
>> The series was sent as a v2. But is this still an RFC?
> I think when Matthew came up with the XE patches we pretty much agreed that this is the way to go.
>
>> If not, more detailed commit messages are a desirable thing.
> Good point, how about:
>
> The enable_signaling callback is called with the same irqsave spinlock held than dma_fence_is_signaled() tries to grab. That will 100% reliable deadlock if that happens.

I guess we could use dma_fence_is_signaled_locked instead. That said, it 
only tries to take the lock (in dma_fence_signal) if fence->ops->signal 
is set, which isn't the case for these fences. That's why this has never 
caused a problem up till now.

Regards,
   Felix


>
> Thanks,
> Christian.
>
>>
>> P.
>>
>>> Signed-off-by: Christian König <christian.koenig@amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c | 6 ------
>>>   1 file changed, 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> index 1ef758ac5076..09c919f72b6c 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_fence.c
>>> @@ -120,12 +120,6 @@ static bool amdkfd_fence_enable_signaling(struct
>>> dma_fence *f)
>>>   {
>>>   	struct amdgpu_amdkfd_fence *fence =
>>> to_amdgpu_amdkfd_fence(f);
>>>   
>>> -	if (!fence)
>>> -		return false;
>>> -
>>> -	if (dma_fence_is_signaled(f))
>>> -		return true;
>>> -
>>>   	if (!fence->svm_bo) {
>>>   		if
>>> (!kgd2kfd_schedule_evict_and_restore_process(fence->mm, f))
>>>   			return true;