2022-05-31 16:26:52

by Sergey Senozhatsky

[permalink] [raw]
Subject: Re: [PATCH] dma-fence: allow dma fence to have their own lock

On (22/05/30 16:55), Christian K?nig wrote:
>
> If you just want to create a single dma_fence which is also only bound to a
> single context you can embed the lock into the fence without much problem.
>
> See how the dma_fence_array does that for example: https://elixir.bootlin.com/linux/latest/source/include/linux/dma-fence-array.h#L37

Christian, I'm not sure I'm following you on the "embed the lock into the
fence without much problem" part. If I understand it correctly this should
be something like:

fences = kmalloc_array(1, sizeof(*fences), GFP_KERNEL);
for_each_fence(...) {

// what spinlock should I use here?

dma_fence_init(&fences[i], .. &lock ..);
dma_fence_get(&fences[i]);
}
fence_array = dma_fence_array_create(1, fences, ....);
sync_file_create(&fence_array->base);


2022-06-01 21:21:18

by Christian König

[permalink] [raw]
Subject: Re: [Linaro-mm-sig] Re: [PATCH] dma-fence: allow dma fence to have their own lock



Am 30.05.22 um 17:45 schrieb Sergey Senozhatsky:
> On (22/05/30 16:55), Christian König wrote:
>> If you just want to create a single dma_fence which is also only bound to a
>> single context you can embed the lock into the fence without much problem.
>>
>> See how the dma_fence_array does that for example: https://elixir.bootlin.com/linux/latest/source/include/linux/dma-fence-array.h#L37
> Christian, I'm not sure I'm following you on the "embed the lock into the
> fence without much problem" part. If I understand it correctly this should
> be something like:
>
> fences = kmalloc_array(1, sizeof(*fences), GFP_KERNEL);
> for_each_fence(...) {
>
> // what spinlock should I use here?
>
> dma_fence_init(&fences[i], .. &lock ..);
> dma_fence_get(&fences[i]);
> }
> fence_array = dma_fence_array_create(1, fences, ....);
> sync_file_create(&fence_array->base);

Well no, that's the high level usage of the dma_fence_array.

What I meant was this here:

struct dma_fence_array {
    struct dma_fence base;

    spinlock_t lock;
...
};

Regards,
Christian.

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