Why
The mutex initialized in xa_init_flags() is not destroyed here on purpose. The reason is that on Linux, the xarray remains usable after a call to xa_destroy(). For instance the i915 DRM driver relies on that during the initialixation of its GuC. Basically, xa_destroy() "resets" the structure to zero but doesn't really destroy it.
This is part of the update of DRM drivers to Linux 6.7.
Sponsored by: The FreeBSD Foundation