| Message ID | 20230406160637.541702-1-dmitry.osipenko@collabora.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Move dma-buf mmap() reservation locking down to exporters | expand |
On Thu, 06 Apr 2023 19:06:30 +0300, 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]. > > [...] Applied, thanks! [4/7] fastrpc: Don't assert held reservation lock for dma-buf mmapping commit: 3f6b4c6f0bd0126f673f3578429239ae3860718b Best regards,
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@rcs0.html [2] https://elixir.bootlin.com/linux/v6.3-rc4/source/drivers/gpu/drm/drm_prime.c#L924 Changelog: v2: - Added ack from Christian König to the DRM patch. - Dropped "fixes" tag from the patches, like was requested by Christian König. The patches don't actually need a backport and merely improve the locking policy. - Dropped "reverts" from the patch titles to prevent them from auto-backporting by the stable bot based on the title. - Added r-b from Emil Velikov and placed the drm_WARN in the drm-shmem patch like he suggested in a comment to v1. - Corrected drm-shmem patch dma_resv_lock(obj->resv) inconsistently used with dma_resv_unlock(shmem->base.resv). Now shmem->base.resv variant is used for all locks/unlocks. Dmitry Osipenko (7): media: videobuf2: Don't assert held reservation lock for dma-buf mmapping dma-buf/heaps: Don't assert held reservation lock for dma-buf mmapping udmabuf: Don't assert held reservation lock for dma-buf mmapping fastrpc: Don't assert held reservation lock for dma-buf mmapping drm: Don't 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 | 208 ++++++++---------- 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, 117 insertions(+), 190 deletions(-)