Android does not support robust futexes, so how to implement a robust mutex?

Question

I found the pthread.h in android ndk does not include robust futexes functions, so what should I do if I want to access a shared memory(mmap) between multiple processes?

PS: Now, I use std::shared_mutex + fcntl, which the shared_mutex is for thread, and the fcntl is for process and would release the lock when process crash. It works, but dirty.