> A less radical change would be to change the global mutex into an rwlock, but unfortunately that is not easily possible either. Unwinding is not a pure librar

> A less radical change would be to change the global mutex into an rwlock, but unfortunately that is not easily possible either. Unwinding is not a pure library function but a back and forth between the unwinder and application/compiler code, and existing code relies upon the fact that it is protected by a global lock. In libgcc the callback from dl_iterate_phdr manipulates shared state, and switching to an rwlock leads to data races. Of course it would make sense to change that, but that would be an ABI break, too.