That's true. But I guess it could be handled by addressed by either the IPC invoker also placing the info on which process to wake into a BPF map before doing t

That's true. But I guess it could be handled by addressed by either the IPC invoker also placing the info on which process to wake into a BPF map before doing the blocking call, and the kernel code using the info to make the scheduling decision. That would however require an additional syscall per IPC. But maybe that informmation could be either cached or derived based on some other BPF visible state, so that it gets cheaper?