drm/amdgpu: fix hang and race in userq destroy

When a queue is hung, the hang_detect_work is the
only way to recover it. However in amdgpu_userq_destroy(),
the hang_detect_work is cancelled too early,
resulting in amdgpu_userq_wait_for_last_fence()
may never return, leaving an uninterruptible dma_fence_wait()
hang there.

To fix this problem, this commit moves the cancelling of
hang_detect_work after amdgpu_userq_wait_for_last_fence(), and it has
to be before the unmap helper, because hang_detect_work resets the
queue, so it races with amdgpu_userq_unmap_helper() for MES operations
and queue state.

This commit splits amdgpu_userq_cleanup() into two parts:

1) amdgpu_userq_detach_doorbell(), which detaches the queue from
userq_doorbell_xa. This has to be called before the cancel, otherwise
the IRQ handlers (for example amdgpu_userq_process_fence_irq)
can re-schedule the hang_detect_work and the cancel is not final.

2) amdgpu_userq_fence_driver_free(), this has to be called after the
unmap helper, because it can release the seq64 slot that the GPU
writes fence values to.

Only one cancel_delayed_work_sync(&queue->hang_detect_work) is needed,
so other redundancies are removed.

Signed-off-by: Zhu Lingshan <lingshan.zhu@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions