I'm trying to implement a thread-safe version of an mruby Rust binding.
mruby has a *mut MRState (a wrapper over mrb_state). You need to pass this *mut MRState when running mruby code. The mruby code has a Rust callback that it can call where it passes the same *mut MRState variable.
This *mut MRState is wrapped in a MRuby struct which I'm trying to make thread-safe. The problem is that if I wrap MRuby in a Mutex, it won't be able to re-enter inside of the Rust-written callback.
I'm currently wrapping MRuby in a RwLock but it's not very useful. The *mut MRState should be in a more permissive lock that lets it run inside of the callbacks.
How can I make MRuby work in both the callback and be forced to wait if called from different threads?
Apart from this, I'm having an issue with the *mut MRState inside MRuby which is not Send & Sync.
struct MRuby {
mrb: *mut MRState,
...
}
This is an example of the callback.
// this callback will be run with a mrb_ function with takes
// *mut MRState as an argument, so it would need to lock
extern "C" callback(...) {
// I need to use MRuby here which will make use of
// its inner *mut MRState
...
}
This is an example of running mruby on a thread. mruby variable here could be an Arc<RwLock<MRuby>>.
thread::spawn(move || {
mruby.run("*mruby code*"); // should run sequentially with
// with a lock on *mut MRState
});
The main reason why I want to implement this is not functionality. Actually, it's catch_panic which I need in order to catch any possible panics from the Rust callback. catch_panic runs in another thread, so I need to make MRuby thread-safe. Rust will stabilize std::panic only in 1.9.0 and until then I would need a working solution that doesn't need Rust nightly.
CORRECTION
Due to a bug in Rust's documentation generation, catch_panic is only marked as deprecated and not as unstable, even though it is. So a very simple solution is to just use std::panic and give up on thread-safety. I'm going to leave the question open, though, in case there is a good answer to this, even though my personal interest is lower now considering the aforementioned.
