The _U_dyn_cancel() routine cancels the registration of the unwind-info for a dynamically generated procedure. Argument di is the pointer to the unw_dyn_info_t structure that describes the procedure's unwind-info.
The _U_dyn_cancel() routine is guaranteed to execute in constant time (in the absence of contention from concurrent calls to _U_dyn_register() or _U_dyn_cancel()).
THREAD AND SIGNAL SAFETY
_U_dyn_cancel() is thread-safe but not safe to use from a signal handler.