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

["Christian König" <christian.koenig@amd.com>]

On 11/6/25 17:37, Kuehling, Felix wrote:
> 
> 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.

But when fence->ops->signal isn't set then why are we calling this?

Regards,
Christian.

> 
> 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;