[gpderetta]

you can longjmp, swapcontext or whatever from a signal handler into another lightweight fiber. The problem is that there is no "until the page arrive" notification. You would have to poll mincore which is awful.

You could of course imagine an ansychronous "mmap complete notification" syscal, but at that point why not just use io_uring, it will be simpler and it has the benefit of actually existing.