asahi: Mark KMS exported resource BOs as shared

Fixes: #13524

Signed-off-by: Asahi Lina <lina@asahilina.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36097>

src/gallium/drivers/asahi/agx_pipe.c

@@ -260,6 +260,15 @@ agx_resource_get_handle(struct pipe_screen *pscreen, struct pipe_context *ctx,
    } else if (handle->type == WINSYS_HANDLE_TYPE_KMS) {
       rsrc_debug(rsrc, "Get handle: %p (KMS)\n", rsrc);
 
+      /* BO must be considered shared at this point.
+       * The seemingly redundant check exists because if the BO is
+       * already shared then mutating the BO would be potentially
+       * racy.
+       */
+      assert(rsrc->bo->flags & AGX_BO_SHAREABLE);
+      if (!(rsrc->bo->flags & AGX_BO_SHARED))
+         rsrc->bo->flags |= AGX_BO_SHARED;
+
       handle->handle = rsrc->bo->handle;
    } else if (handle->type == WINSYS_HANDLE_TYPE_FD) {
       int fd = agx_bo_export(dev, rsrc->bo);