amdgpu_ttm_tt_unpopulate can be called during bo_destroy. The dmabuf->resv
must not be held by the caller or dma_buf_detach will deadlock. This is
probably not the right fix. I get a recursive lock warning with the
reservation held in ttm_bo_release. Should unmap_attachment move to
backend_unbind instead?

Signed-off-by: Felix Kuehling <felix.kuehl...@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 936b3cfdde55..257750921eed 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1216,9 +1216,22 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_device 
*bdev,
 
        if (ttm->sg && gtt->gobj->import_attach) {
                struct dma_buf_attachment *attach;
+               bool locked;
 
                attach = gtt->gobj->import_attach;
+               /* FIXME: unpopulate can be called during bo_destroy.
+                * The dmabuf->resv must not be held by the caller or
+                * dma_buf_detach will deadlock. This is probably not
+                * the right fix. I get a recursive lock warning with the
+                * reservation held in ttm_bo_releas.. Should
+                * unmap_attachment move to backend_unbind instead?
+                */
+               locked = dma_resv_is_locked(attach->dmabuf->resv);
+               if (!locked)
+                       dma_resv_lock(attach->dmabuf->resv, NULL);
                dma_buf_unmap_attachment(attach, ttm->sg, DMA_BIDIRECTIONAL);
+               if (!locked)
+                       dma_resv_unlock(attach->dmabuf->resv);
                ttm->sg = NULL;
                return;
        }
-- 
2.31.1

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