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 Dmitry Osipenko (7): Revert "media: videobuf2: Assert held reservation lock for dma-buf mmapping" Revert "dma-buf/heaps: Assert held reservation lock for dma-buf mmapping" Revert "udmabuf: Assert held reservation lock for dma-buf mmapping" Revert "fastrpc: Assert held reservation lock for dma-buf mmapping" Revert "drm: Assert held reservation lock for dma-buf mmapping" dma-buf: Change locking policy for mmap() drm/shmem-helper: Switch to reservation lock drivers/dma-buf/dma-buf.c | 17 +- drivers/dma-buf/heaps/cma_heap.c | 3 - drivers/dma-buf/heaps/system_heap.c | 3 - drivers/dma-buf/udmabuf.c | 2 - drivers/gpu/drm/drm_gem_shmem_helper.c | 217 ++++++++---------- drivers/gpu/drm/drm_prime.c | 2 - drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 2 - drivers/gpu/drm/lima/lima_gem.c | 8 +- drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c | 2 - drivers/gpu/drm/panfrost/panfrost_drv.c | 7 +- .../gpu/drm/panfrost/panfrost_gem_shrinker.c | 6 +- drivers/gpu/drm/panfrost/panfrost_mmu.c | 19 +- drivers/gpu/drm/tegra/gem.c | 2 - .../common/videobuf2/videobuf2-dma-contig.c | 3 - .../media/common/videobuf2/videobuf2-dma-sg.c | 3 - .../common/videobuf2/videobuf2-vmalloc.c | 3 - drivers/misc/fastrpc.c | 3 - include/drm/drm_gem_shmem_helper.h | 14 +- 18 files changed, 123 insertions(+), 193 deletions(-) -- 2.39.2
