[PATCH v3 0/9] Move all drivers to a common dma-buf locking convention

Dmitry Osipenko
2022-08-24T10:23:46Z

Hello,

This series moves all drivers to a dynamic dma-buf locking specification.
From now on all dma-buf importers are made responsible for holding
dma-buf's reservation lock around all operations performed over dma-bufs
in accordance to the locking specification. This allows us to utilize
reservation lock more broadly around kernel without fearing of a potential
deadlocks.

This patchset passes all i915 selftests. It was also tested using VirtIO,
Panfrost, Lima, Tegra, udmabuf, AMDGPU and Nouveau drivers. I tested cases
of display+GPU, display+V4L and GPU+V4L dma-buf sharing (where appropriate),
which covers majority of kernel drivers since rest of the drivers share
same or similar code paths.

Changelog:

v3: - Factored out dma_buf_mmap_unlocked() and attachment functions
into aseparate patches, like was suggested by Christian König.

- Corrected and factored out dma-buf locking documentation into
a separate patch, like was suggested by Christian König.

- Intel driver dropped the reservation locking fews days ago from
its BO-release code path, but we need that locking for the imported
GEMs because in the end that code path unmaps the imported GEM.
So I added back the locking needed by the imported GEMs, updating
the "dma-buf attachment locking specification" patch appropriately.

- Tested Nouveau+Intel dma-buf import/export combo.

- Tested udmabuf import to i915/Nouveau/AMDGPU.

- Fixed few places in Etnaviv, Panfrost and Lima drivers that I missed
to switch to locked dma-buf vmapping in the drm/gem: Take reservation
lock for vmap/vunmap operations" patch. In a result invalidated the
Christian's r-b that he gave to v2.

- Added locked dma-buf vmap/vunmap functions that are needed for fixing
vmappping of Etnaviv, Panfrost and Lima drivers mentioned above.
I actually had this change stashed for the drm-shmem shrinker patchset,
but then realized that it's already needed by the dma-buf patches.
Also improved my tests to better cover these code paths.

v2: - Changed locking specification to avoid problems with a cross-driver
ww locking, like was suggested by Christian König. Now the attach/detach
callbacks are invoked without the held lock and exporter should take the
lock.

- Added "locking convention" documentation that explains which dma-buf
functions and callbacks are locked/unlocked for importers and exporters,
which was requested by Christian König.

- Added ack from Tomasz Figa to the V4L patches that he gave to v1.

Dmitry Osipenko (9):
dma-buf: Add _unlocked postfix to function names
dma-buf: Add locked variant of dma_buf_vmap/vunmap()
drm/gem: Take reservation lock for vmap/vunmap operations
dma-buf: Move dma_buf_vmap/vunmap_unlocked() to dynamic locking
specification
dma-buf: Move dma_buf_mmap_unlocked() to dynamic locking specification
dma-buf: Move dma-buf attachment to dynamic locking specification
dma-buf: Document dynamic locking convention
media: videobuf2: Stop using internal dma-buf lock
dma-buf: Remove internal lock

Documentation/driver-api/dma-buf.rst | 6 +
drivers/dma-buf/dma-buf.c | 276 ++++++++++++++----
drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 4 +-
drivers/gpu/drm/armada/armada_gem.c | 14 +-
drivers/gpu/drm/drm_client.c | 4 +-
drivers/gpu/drm/drm_gem.c | 24 ++
drivers/gpu/drm/drm_gem_dma_helper.c | 6 +-
drivers/gpu/drm/drm_gem_framebuffer_helper.c | 6 +-
drivers/gpu/drm/drm_gem_shmem_helper.c | 2 +-
drivers/gpu/drm/drm_gem_ttm_helper.c | 9 +-
drivers/gpu/drm/drm_prime.c | 12 +-
drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c | 4 +-
drivers/gpu/drm/exynos/exynos_drm_gem.c | 2 +-
drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 6 +-
drivers/gpu/drm/i915/gem/i915_gem_object.c | 12 +
.../drm/i915/gem/selftests/i915_gem_dmabuf.c | 20 +-
drivers/gpu/drm/lima/lima_sched.c | 4 +-
drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c | 8 +-
drivers/gpu/drm/panfrost/panfrost_dump.c | 4 +-
drivers/gpu/drm/panfrost/panfrost_perfcnt.c | 6 +-
drivers/gpu/drm/qxl/qxl_object.c | 17 +-
drivers/gpu/drm/qxl/qxl_prime.c | 4 +-
drivers/gpu/drm/tegra/gem.c | 27 +-
drivers/infiniband/core/umem_dmabuf.c | 11 +-
.../common/videobuf2/videobuf2-dma-contig.c | 26 +-
.../media/common/videobuf2/videobuf2-dma-sg.c | 23 +-
.../common/videobuf2/videobuf2-vmalloc.c | 17 +-
.../platform/nvidia/tegra-vde/dmabuf-cache.c | 12 +-
drivers/misc/fastrpc.c | 12 +-
drivers/xen/gntdev-dmabuf.c | 14 +-
include/drm/drm_gem.h | 3 +
include/linux/dma-buf.h | 57 ++--
32 files changed, 410 insertions(+), 242 deletions(-)

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2.37.2