make stdin async

crsn/src/runtime/fault.rs

@@ -86,6 +86,9 @@ pub enum Fault {
 
     #[error("Root routine returned or yielded a value")]
     RootReturned,
+
+    #[error("System IO error: {0}")]
+    IOError(#[from] std::io::Error),
 }
 
 #[derive(Error, Debug)]

crsn/src/runtime/run_thread.rs

@@ -153,7 +153,9 @@ impl RunThread {
                     }
                 }
                 Err(Fault::Blocked) => {
-                    // Do not advance, the last instruction will be re-tried
+                    trace!("Thread reports being blocked!");
+                    self.state.cr.frame.pc = orig_pc; // Retry
+                    self.state.cr.cr_state = CoroutineState::Ready;
                     want_switch = true;
                 }
                 Err(e) => {
@@ -191,18 +193,20 @@ impl RunThread {
 
                     let mut candidate = None;
                     let mut closest_due = None;
-                    for _ in 0..self.state.parked.len() {
+                    'findbest: for _ in 0..self.state.parked.len() {
                         if let Some(mut rt) = self.state.parked.pop_front() {
                             match rt.cr_state {
                                 CoroutineState::Ready => {
+                                    trace!("Found READY thread to run next");
                                     candidate = Some(rt);
-                                    break;
+                                    break 'findbest;
                                 }
                                 CoroutineState::Sleep { due } => {
                                     if due <= now {
+                                        trace!("Found DUE sleeping thread to run next");
                                         rt.cr_state = CoroutineState::Ready;
                                         candidate = Some(rt);
-                                        break;
+                                        break 'findbest;
                                     } else {
                                         match closest_due {
                                             Some(d) => {
@@ -234,10 +238,15 @@ impl RunThread {
                         self.state.start_task_switching();
 
                     } else if let Some(due) = closest_due {
+                        if self.state.cr.cr_state == CoroutineState::Ready {
+                            trace!("No candidate found to run, retry same thread.");
+                            // Let it run another quantum, maybe it was just blocked
+                            continue 'run;
+                        }
+
                         let time = due.saturating_duration_since(now);
                         trace!("No thread to switch to, sleep {:?}", time);
                         thread::sleep(time);
-
                         continue 'next;
                     } else {
                         // Nothing to run?