Fix a scheduling fairness issue

examples/ctrl-c.rs

@@ -20,7 +20,7 @@ fn main() {
     smol::run(async {
         println!("Waiting for Ctrl-C...");
 
-        // Receive a message that indicates the Ctrl-C signal occured.
+        // Receive a message that indicates the Ctrl-C signal occurred.
         ctrl_c.recv().await;
 
         println!("Done!");

examples/unix-signal.rs

@@ -20,7 +20,7 @@ fn main() -> std::io::Result<()> {
         signal_hook::pipe::register(signal_hook::SIGINT, a)?;
         println!("Waiting for Ctrl-C...");
 
-        // Receive a byte that indicates the Ctrl-C signal occured.
+        // Receive a byte that indicates the Ctrl-C signal occurred.
         b.read_exact(&mut [0]).await?;
 
         println!("Done!");

src/multitask.rs

@@ -346,6 +346,7 @@ impl Worker {
                             self.global.queue.push(err.into_inner()).unwrap();
                             self.global.notify();
                         }
+                        self.local.flush().unwrap();
                     }
 
                     return true;

src/reactor.rs

@@ -251,13 +251,16 @@ impl ReactorLock<'_> {
 
         // Block on I/O events.
         match self.reactor.sys.wait(&mut self.events, timeout) {
-            // The timeout was hit so fire ready timers.
+            // No I/O events occurred.
             Ok(0) => {
-                self.reactor.fire_timers();
+                if timeout != Some(Duration::from_secs(0)) {
+                    // The non-zero timeout was hit so fire ready timers.
+                    self.reactor.fire_timers();
+                }
                 Ok(())
             }
 
-            // At least one I/O event occured.
+            // At least one I/O event occurred.
             Ok(_) => {
                 // Iterate over sources in the event list.
                 let sources = self.reactor.sources.lock();