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drm_sched_backend_ops.run_job() returns a dma_fence for the scheduler. That fence is signalled by the driver once the hardware completed the associated job. The scheduler does not increment the reference count on that fence, but implicitly expects to inherit this fence from run_job(). This is relatively subtle and prone to misunderstandings. This implies that, to keep a reference for itself, a driver needs to call dma_fence_get() in addition to dma_fence_init() in that callback. It's further complicated by the fact that the scheduler even decrements the refcount in drm_sched_run_job_work() since it created a new reference in drm_sched_fence_scheduled(). It does, however, still use its pointer to the fence after calling dma_fence_put() - which is safe because of the aforementioned new reference, but actually still violates the refcounting rules. Move the call to dma_fence_put() to the position behind the last usage of the fence. Suggested-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Philipp Stanner <pstanner@redhat.com> Reviewed-by: Danilo Krummrich <dakr@kernel.org> Signed-off-by: Philipp Stanner <phasta@kernel.org> Link: https://patchwork.freedesktop.org/patch/msgid/20250305130551.136682-4-phasta@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 reStructuredText markup notation.
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.