linux-kernel - Re: [PATCH] dma-fence: allow dma fence to have their own lock

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Message-ID: <YpTmhixkV7+yh6wo@google.com>
Date:   Tue, 31 May 2022 00:45:10 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Christian König <christian.koenig@....com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Ricardo Ribalda <ribalda@...omium.org>,
        Christoph Hellwig <hch@...radead.org>,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma-fence: allow dma fence to have their own lock

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);