Am 12.03.25 um 16:06 schrieb SRINIVASAN SHANMUGAM:
>
> On 3/7/2025 7:18 PM, Christian König wrote:
>> This allows using amdgpu_sync even without peeking into the fences for a
>> long time.
>>
>> Signed-off-by: Christian König <christian.koe...@amd.com>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c | 13 +++++++++----
>> 1 file changed, 9 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>> index 86c17a8946f5..bfe12164d27d 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>> @@ -135,11 +135,16 @@ static bool amdgpu_sync_add_later(struct amdgpu_sync
>> *sync, struct dma_fence *f)
>> struct amdgpu_sync_entry *e;
>> hash_for_each_possible(sync->fences, e, node, f->context) {
>> - if (unlikely(e->fence->context != f->context))
>> - continue;
>> + if (dma_fence_is_signaled(e->fence)) {
>> + dma_fence_put(e->fence);
>> + e->fence = dma_fence_get(f);
>> + return true;
>> + }
>> - amdgpu_sync_keep_later(&e->fence, f);
>> - return true;
>> + if (likely(e->fence->context == f->context)) {
>> + amdgpu_sync_keep_later(&e->fence, f);
> --> The call to amdgpu_sync_keep_later(&e->fence, f); ensures that the new
> fence is tracked for future synchronization., ie., so If the driver only
> replaced the old fence without keeping a reference to the new one of the next
> job or second job for example, it could lead to situations where the
> synchronization state is lost. This could cause race conditions where one job
> might proceed before another job has completed, leading to errors. , so this
> is " amdgpu_sync_keep_later(&e->fence, f);" done, for tracking purpose of
> next job/second job, if we have multiple jobs in gang submissions of same
> context/client, is my understanding is correct here pls?
Your questions is not easy to understand, but I think your understanding is
correct.
Basically if you have submissions A,B,C to the same ring buffer and the HW
guarantees that they execute in order you only need to keep a reference to C to
wait for A and B as well.
Regards,
Christian.
>> + return true;
>> + }
>> }
>> return false;
>> }
