[PATCH] drm/amdgpu: only keep most recent fence for each context

[Yadav, Arvind]

On 4/15/2025 7:53 PM, Christian König wrote:
> Am 15.04.25 um 16:18 schrieb Arvind Yadav:
>> Mesa passes shared bo, fence syncobj to userq_ioctl.
>> There can be duplicates here or some fences that are old.
>> This patch is remove duplicates fence and only keep
>> the most recent fence for each context.
>>
>> Cc: Alex Deucher <alexander.deucher at amd.com>
>> Cc: Christian König <christian.koenig at amd.com>
>> Cc: Sunil Khatri <sunil.khatri at amd.com>
>> Cc: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam at amd.com>
>> Signed-off-by: Arvind Yadav <arvind.yadav at amd.com>
>> ---
>>   .../gpu/drm/amd/amdgpu/amdgpu_userq_fence.c   | 37 +++++++++++++++++++
>>   1 file changed, 37 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
>> index a4953d668972..9a09d545ceb5 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq_fence.c
>> @@ -25,6 +25,7 @@
>>   #include <linux/kref.h>
>>   #include <linux/slab.h>
>>   #include <linux/dma-fence-unwrap.h>
>> +#include <linux/sort.h>
>>   
>>   #include <drm/drm_exec.h>
>>   #include <drm/drm_syncobj.h>
>> @@ -584,6 +585,24 @@ int amdgpu_userq_signal_ioctl(struct drm_device *dev, void *data,
>>   #endif
>>   
>>   #ifdef CONFIG_DRM_AMDGPU_NAVI3X_USERQ
>> +static int fence_cmp(const void *_a, const void *_b)
>> +{
>> +	struct dma_fence *a = *(struct dma_fence **)_a;
>> +	struct dma_fence *b = *(struct dma_fence **)_b;
>> +
>> +	if (a->context < b->context)
>> +		return -1;
>> +	else if (a->context > b->context)
>> +		return 1;
>> +
>> +	if (dma_fence_is_later(b, a))
>> +		return 1;
>> +	else if (dma_fence_is_later(a, b))
>> +		return -1;
>> +
>> +	return 0;
>> +}
>> +
>>   int amdgpu_userq_wait_ioctl(struct drm_device *dev, void *data,
>>   			    struct drm_file *filp)
>>   {
>> @@ -840,6 +859,24 @@ int amdgpu_userq_wait_ioctl(struct drm_device *dev, void *data,
>>   			fences[num_fences++] = fence;
>>   		}
>>   
>> +		if (num_fences > 1) {
>> +			int j = 0;
>> +
>> +			sort(fences, num_fences, sizeof(*fences), fence_cmp, NULL);
>> +
>> +			/*
>> +			 * Only keep the most recent fence for each context.
>> +			 */
>> +			for (int i = 1; i < num_fences; i++) {
>> +				if (fences[i]->context == fences[j]->context)
>> +					dma_fence_put(fences[i]);
>> +				else
>> +					fences[++j] = fences[i];
>> +			}
>> +
>> +			num_fences = ++j;
>> +		}
>> +
> We already have the same code in drivers/dma-buf/dma-fence-unwrap.c.
>
> I suggest to export this code from drivers/dma-buf/dma-fence-unwrap.c and just use it here as well.
>
> Something like num_fences = dma_fence_shrink_array(fences, num_fences)
Noted.
>
> Regards,
> Christian.
>
>>   		for (i = 0, cnt = 0; i < num_fences; i++) {
>>   			struct amdgpu_userq_fence_driver *fence_drv;
>>   			struct amdgpu_userq_fence *userq_fence;