Hi everybody, The idea of ref-counting dma_resv or ww_mutex came up multiple times from different people, but so far at least I have abandoned that as to complicated to implement considering how widely used that object is.
Thanks to AI I gave the task to refcount dma_resv to Claude Sonet 4 just to check how horrible it would look like. Well turns out that this is actually a cleanup we should most likely aim for and I'm really wondering why we haven't done it like this in the first place. Not only resolves it a bunch of issues with dma_resv instances shared by multiple GEM objects (we just recently had a bunch of patches for that on the mailing list), but also allows TTM to implement it's delayed delete handling without any zombie resurrection or similar hacks and DMA-buf to have better contention handling on map/pin in the future. This patch set here is now the idea full flashed out. I smoke tested it with amdgpu, self tests and checked everything with kmemleak and of hand it seems to work. Patch #1 introduces an interim allocated flag to allow switching users over to the new interface one by one. Patch #10 then removes that flag again after everything is done. While AI is an automated tool I distrust it to always generate the same code. So better using a defensive approach on changing things. Please review and comment. Cheers, Christian.
