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[ Upstream commit6e11ea9de9] amdgpu only uses shared-fences internally, but dmabuf importers rely on implicit write hazard tracking via the reservation_object.fence_excl. For example, the importer use the write hazard for timing a page flip to only occur after the exporter has finished flushing its write into the surface. As such, on exporting a dmabuf, we must either flush all outstanding fences (for we do not know which are writes and should have been exclusive) or alternatively create a new exclusive fence that is the composite of all the existing shared fences, and so will only be signaled when all earlier fences are signaled (ensuring that we can not be signaled before the completion of any earlier write). v2: reservation_object is already locked by amdgpu_bo_reserve() v3: Replace looping with get_fences_rcu and special case the promotion of a single shared fence directly to an exclusive fence, bypassing the fence array. v4: Drop the fence array ref after assigning to reservation_object Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107341 Testcase: igt/amd_prime/amd-to-i915 References:8e94a46c17("drm/amdgpu: Attach exclusive fence to prime exported bo's. (v5)") Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: "Christian König" <christian.koenig@amd.com> Reviewed-by: "Christian König" <christian.koenig@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.