[gpderetta]

I think what doors do is rendezvous synchronization: the caller is atomically blocked as the callee is unblocked (and vice versa on return). I don't think there is an efficient way to do that with just plain POSIX primitives or even with Linux specific syscalls (Binder and io_uring possibly might).

[xoranth]

Sounds a bit like Google's proposal for a `switchto_switch` syscall [1] that would allow for cooperative multithreading bypassing the scheduler.

(the descendants of that proposal is `sched_ext`, so maybe it is possible to implement doors in eBPF + sched_ext?)

[1]: https://youtu.be/KXuZi9aeGTw?t=900