Re: [PATCH v4 00/21] Move all drivers to a common dma-buf locking convention

["Christian König" <christian.koenig@amd.com>]

Hi Dmitry,

I've gone over this multiple times now and while it is still possible 
that we missed something I think that this should land now.

The whole topic is just to complicated that we can 100% sure guarantee 
that there isn't anything wrong with the locking, but lockdep and driver 
testing should allow us to quickly find remaining issues.

Do you have commit rights to drm-misc-next or should I push it?

Thanks,
Christian.

Am 31.08.22 um 17:37 schrieb Dmitry Osipenko:
> 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:
>
> v4: - Added dma_buf_mmap() to the "locking convention" documentation,
>        which was missed by accident in v3.
>
>      - Added acks from Christian König, Tomasz Figa and Hans Verkuil that
>        they gave to couple v3 patches.
>
>      - Dropped the "_unlocked" postfix from function names that don't have
>        the locked variant, as was requested by Christian König.
>
>      - Factored out the per-driver preparations into separate patches
>        to ease reviewing of the changes, which is now doable without the
>        global dma-buf functions renaming.
>
>      - Factored out the dynamic locking convention enforcements into separate
>        patches which add the final dma_resv_assert_held(dmabuf->resv) to the
>        dma-buf API functions.
>
> 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 (21):
>    dma-buf: Add unlocked variant of vmapping functions
>    dma-buf: Add unlocked variant of attachment-mapping functions
>    drm/gem: Take reservation lock for vmap/vunmap operations
>    drm/prime: Prepare to dynamic dma-buf locking specification
>    drm/armada: Prepare to dynamic dma-buf locking specification
>    drm/i915: Prepare to dynamic dma-buf locking specification
>    drm/omapdrm: Prepare to dynamic dma-buf locking specification
>    drm/tegra: Prepare to dynamic dma-buf locking specification
>    drm/etnaviv: Prepare to dynamic dma-buf locking specification
>    RDMA/umem: Prepare to dynamic dma-buf locking specification
>    misc: fastrpc: Prepare to dynamic dma-buf locking specification
>    xen/gntdev: Prepare to dynamic dma-buf locking specification
>    media: videobuf2: Prepare to dynamic dma-buf locking specification
>    media: tegra-vde: Prepare to dynamic dma-buf locking specification
>    dma-buf: Move dma_buf_vmap() to dynamic locking specification
>    dma-buf: Move dma_buf_attach() to dynamic locking specification
>    dma-buf: Move dma_buf_map_attachment() to dynamic locking
>      specification
>    dma-buf: Move dma_buf_mmap() to dynamic locking specification
>    dma-buf: Document dynamic locking convention
>    media: videobuf2: Stop using internal dma-buf lock
>    dma-buf: Remove obsoleted internal lock
>
>   Documentation/driver-api/dma-buf.rst          |   6 +
>   drivers/dma-buf/dma-buf.c                     | 211 +++++++++++++++---
>   drivers/gpu/drm/armada/armada_gem.c           |   8 +-
>   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_ttm_helper.c          |   9 +-
>   drivers/gpu/drm/drm_prime.c                   |   6 +-
>   drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c   |   2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c    |   2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_object.c    |  12 +
>   .../drm/i915/gem/selftests/i915_gem_dmabuf.c  |  16 +-
>   drivers/gpu/drm/lima/lima_sched.c             |   4 +-
>   drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c     |   4 +-
>   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                   |  17 +-
>   drivers/infiniband/core/umem_dmabuf.c         |   7 +-
>   .../common/videobuf2/videobuf2-dma-contig.c   |  22 +-
>   .../media/common/videobuf2/videobuf2-dma-sg.c |  19 +-
>   .../common/videobuf2/videobuf2-vmalloc.c      |  17 +-
>   .../platform/nvidia/tegra-vde/dmabuf-cache.c  |   6 +-
>   drivers/misc/fastrpc.c                        |   6 +-
>   drivers/xen/gntdev-dmabuf.c                   |   8 +-
>   include/drm/drm_gem.h                         |   3 +
>   include/linux/dma-buf.h                       |  17 +-
>   29 files changed, 318 insertions(+), 155 deletions(-)
>