Move all drivers to a common dma-buf locking convention [LWN.net]

From:		Dmitry Osipenko <dmitry.osipenko-AT-collabora.com>
To:		David Airlie <airlied-AT-linux.ie>, Gerd Hoffmann <kraxel-AT-redhat.com>, Gurchetan Singh <gurchetansingh-AT-chromium.org>, Chia-I Wu <olvaffe-AT-gmail.com>, Daniel Vetter <daniel-AT-ffwll.ch>, Daniel Almeida <daniel.almeida-AT-collabora.com>, Gert Wollny <gert.wollny-AT-collabora.com>, Gustavo Padovan <gustavo.padovan-AT-collabora.com>, Daniel Stone <daniel-AT-fooishbar.org>, Tomeu Vizoso <tomeu.vizoso-AT-collabora.com>, Maarten Lankhorst <maarten.lankhorst-AT-linux.intel.com>, Maxime Ripard <mripard-AT-kernel.org>, Thomas Zimmermann <tzimmermann-AT-suse.de>, Rob Clark <robdclark-AT-gmail.com>, Sumit Semwal <sumit.semwal-AT-linaro.org>, Christian König <christian.koenig-AT-amd.com>, "Pan, Xinhui" <Xinhui.Pan-AT-amd.com>, Thierry Reding <thierry.reding-AT-gmail.com>, Tomasz Figa <tfiga-AT-chromium.org>, Marek Szyprowski <m.szyprowski-AT-samsung.com>, Mauro Carvalho Chehab <mchehab-AT-kernel.org>, Alex Deucher <alexander.deucher-AT-amd.com>, Jani Nikula <jani.nikula-AT-linux.intel.com>, Joonas Lahtinen <joonas.lahtinen-AT-linux.intel.com>, Rodrigo Vivi <rodrigo.vivi-AT-intel.com>, Tvrtko Ursulin <tvrtko.ursulin-AT-linux.intel.com>, Thomas Hellström <thomas_os-AT-shipmail.org>
Subject:		[PATCH v2 0/5] Move all drivers to a common dma-buf locking convention
Date:		Mon, 25 Jul 2022 18:18:34 +0300
Message-ID:		<20220725151839.31622-1-dmitry.osipenko@collabora.com>
Cc:		dri-devel-AT-lists.freedesktop.org, linux-kernel-AT-vger.kernel.org, Dmitry Osipenko <digetx-AT-gmail.com>, linux-media-AT-vger.kernel.org, linaro-mm-sig-AT-lists.linaro.org, amd-gfx-AT-lists.freedesktop.org, intel-gfx-AT-lists.freedesktop.org, kernel-AT-collabora.com, virtualization-AT-lists.linux-foundation.org, spice-devel-AT-lists.freedesktop.org, linux-rdma-AT-vger.kernel.org, linux-arm-msm-AT-vger.kernel.org
Archive-link:		Article

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 and Tegra drivers. I tested cases of display+GPU,
display+V4L and GPU+V4L dma-buf sharing, which covers majority of kernel
drivers since rest of the drivers share same or similar code paths.

Changelog:

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 (5):
  dma-buf: Add _unlocked postfix to function names
  drm/gem: Take reservation lock for vmap/vunmap operations
  dma-buf: Move all dma-bufs to dynamic locking specification
  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                     | 253 +++++++++++++-----
 drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c   |   4 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.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_cma_helper.c          |   6 +-
 drivers/gpu/drm/drm_gem_framebuffer_helper.c  |   6 +-
 drivers/gpu/drm/drm_gem_shmem_helper.c        |   6 +-
 drivers/gpu/drm/drm_prime.c                   |  12 +-
 drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c   |   6 +-
 drivers/gpu/drm/exynos/exynos_drm_gem.c       |   2 +-
 drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c    |  14 +-
 .../drm/i915/gem/selftests/i915_gem_dmabuf.c  |  20 +-
 drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c     |   8 +-
 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                       |  71 ++---
 28 files changed, 372 insertions(+), 254 deletions(-)

-- 
2.36.1