Re: [PATCH 05/18] dma-buf: use inline lock for the stub fence

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

On 11/27/25 11:50, Philipp Stanner wrote:
> On Thu, 2025-11-13 at 15:51 +0100, Christian König wrote:
>> Using the inline lock is now the recommended way for dma_fence implementations.
>>
>> So use this approach for the framework internal fences as well.
> 
> nit:
> s/framework/framework's
> 
>>
>> Also saves about 4 bytes for the external spinlock.
> 
> On all platforms or just AMD64?

I think most if not all platforms. Or is anybody really using 64bits for a spinlock?

Christian.

> 
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
>> ---
>>  drivers/dma-buf/dma-fence.c | 20 ++++----------------
>>  1 file changed, 4 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
>> index 9a5aa9e44e13..e6d26c2e0391 100644
>> --- a/drivers/dma-buf/dma-fence.c
>> +++ b/drivers/dma-buf/dma-fence.c
>> @@ -24,7 +24,6 @@ EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
>>  EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
>>  EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
>>  
>> -static DEFINE_SPINLOCK(dma_fence_stub_lock);
>>  static struct dma_fence dma_fence_stub;
>>  
>>  /*
>> @@ -123,12 +122,8 @@ static const struct dma_fence_ops dma_fence_stub_ops = {
>>  
>>  static int __init dma_fence_init_stub(void)
>>  {
>> -	dma_fence_init(&dma_fence_stub, &dma_fence_stub_ops,
>> -		       &dma_fence_stub_lock, 0, 0);
>> -
>> -	set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
>> -		&dma_fence_stub.flags);
> 
> That change is unrelated, isn't it? Enlarges the diff and breaks git-
> blame.
> 
>> -
>> +	dma_fence_init(&dma_fence_stub, &dma_fence_stub_ops, NULL, 0, 0);
>> +	set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &dma_fence_stub.flags);
>>  	dma_fence_signal(&dma_fence_stub);
>>  	return 0;
>>  }
>> @@ -160,16 +155,9 @@ struct dma_fence *dma_fence_allocate_private_stub(ktime_t timestamp)
>>  	if (fence == NULL)
>>  		return NULL;
>>  
>> -	dma_fence_init(fence,
>> -		       &dma_fence_stub_ops,
>> -		       &dma_fence_stub_lock,
>> -		       0, 0);
>> -
>> -	set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
>> -		&fence->flags);
> 
> Same.
> 
>> -
>> +	dma_fence_init(fence, &dma_fence_stub_ops, NULL, 0, 0);
>> +	set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
>>  	dma_fence_signal_timestamp(fence, timestamp);
>> -
> 
> I wouldn't remove that empty line (nit).
> 
>>  	return fence;
>>  }
>>  EXPORT_SYMBOL(dma_fence_allocate_private_stub);
>