Defined in 3 files as a macro:
- sys/cddl/contrib/opensolaris/uts/common/sys/callb.h, line 27 (as a macro)
- sys/contrib/openzfs/include/os/freebsd/spl/sys/callb.h, line 27 (as a macro)
- sys/contrib/openzfs/lib/libspl/include/sys/callb.h, line 28 (as a macro)