First this happens:

1) amdgpu_cs_flush (lock bo_fence_lock)
   -> amdgpu_add_fence_dependency
   -> os_wait_until_zero (wait for submission_in_progress) - WAITING

2) amdgpu_bo_create
   -> pb_cache_reclaim_buffer (lock pb_cache::mutex)
   -> pb_cache_is_buffer_compat
   -> amdgpu_bo_wait (lock bo_fence_lock) - WAITING

So both bo_fence_lock and pb_cache::mutex are held. amdgpu_bo_create can't
continue. amdgpu_cs_flush is waiting for the CS ioctl to finish the job,
but the CS ioctl is trying to release a buffer:

3) amdgpu_cs_submit_ib (CS thread - job entrypoint)
   -> amdgpu_cs_context_cleanup
   -> pb_reference
   -> pb_destroy
   -> amdgpu_bo_destroy_or_cache
   -> pb_cache_add_buffer (lock pb_cache::mutex) - DEADLOCK

The simple solution is not to wait for submission_in_progress, which we
need in order to create the list of dependencies for the CS ioctl. Instead
of building the list of dependencies as a direct input to the CS ioctl,
build the list of dependencies as a list of fences, and make the final list
of dependencies in the CS thread itself.

Therefore, amdgpu_cs_flush doesn't have to wait and can continue.
Then, amdgpu_bo_create can continue and return. And then amdgpu_cs_submit_ib
can continue.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101294



Cc: 17.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>