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use core::marker::PhantomData;
use core::ptr;
use core::sync::atomic::{AtomicBool, Ordering};
use super::{raw, Spawner};
/// global atomic used to keep track of whether there is work to do since sev() is not available on Xtensa
///
static SIGNAL_WORK_THREAD_MODE: AtomicBool = AtomicBool::new(false);
/// Xtensa Executor
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
}
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
Self {
// use Signal_Work_Thread_Mode as substitute for local interrupt register
inner: raw::Executor::new(
|_| {
SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
},
ptr::null_mut(),
),
not_send: PhantomData,
}
}
/// Run the executor.
///
/// The `init` closure is called with a [`Spawner`] that spawns tasks on
/// this executor. Use it to spawn the initial task(s). After `init` returns,
/// the executor starts running the tasks.
///
/// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
/// for example by passing it as an argument to the initial tasks.
///
/// This function requires `&'static mut self`. This means you have to store the
/// Executor instance in a place where it'll live forever and grants you mutable
/// access. There's a few ways to do this:
///
/// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
/// - a `static mut` (unsafe)
/// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
///
/// This function never returns.
pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
init(self.inner.spawner());
loop {
unsafe {
self.inner.poll();
// we do not care about race conditions between the load and store operations, interrupts
// will only set this value to true.
// if there is work to do, loop back to polling
// TODO can we relax this?
critical_section::with(|_| {
if SIGNAL_WORK_THREAD_MODE.load(Ordering::SeqCst) {
SIGNAL_WORK_THREAD_MODE.store(false, Ordering::SeqCst);
} else {
// waiti sets the PS.INTLEVEL when slipping into sleep
// because critical sections in Xtensa are implemented via increasing
// PS.INTLEVEL the critical section ends here
// take care not add code after `waiti` if it needs to be inside the CS
core::arch::asm!("waiti 0"); // critical section ends here
}
});
}
}
}
}
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