On 5/30/23 01:39, Dmitry Osipenko wrote: > This patchset makes dma-buf exporters responisble for taking care of > the reservation lock. I also included patch that moves drm-shmem to use > reservation lock, to let CI test the whole set. I'm going to take all > the patches via the drm-misc tree, please give an ack. > > Previous policy stated that dma-buf core takes the lock around mmap() > callback. Which meant that both importers and exporters shouldn't touch > the reservation lock in the mmap() code path. This worked well until > Intel-CI found a deadlock problem in a case of self-imported dma-buf [1]. > > The problem happens when userpace mmaps a self-imported dma-buf, i.e. > mmaps the dma-buf FD. DRM core treats self-imported dma-bufs as own GEMs > [2]. There is no way to differentiate a prime GEM from a normal GEM for > drm-shmem in drm_gem_shmem_mmap(), which resulted in a deadlock problem > for drm-shmem mmap() code path once it's switched to use reservation lock. > > It was difficult to fix the drm-shmem problem without adjusting dma-buf > locking policy. In parctice not much changed from importers perspective > because previosly dma-buf was taking the lock in between of importers > and exporters. Now this lock is shifted down to exporters. > > [1] https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_114671v2/shard-snb5/igt@prime_vgem@sync@xxxxxxxxx > [2] https://elixir.bootlin.com/linux/v6.3-rc4/source/drivers/gpu/drm/drm_prime.c#L924 Applied to misc-next -- Best regards, Dmitry
