fix(iour): wait if thread pool is full

compio-driver/src/iour/mod.rs

@@ -139,13 +139,17 @@ impl Driver {
         }
     }
 
-    fn poll_entries(&mut self, entries: &mut OutEntries) -> bool {
+    fn poll_blocking(&mut self, entries: &mut OutEntries) {
         // Cheaper than pop.
         if !self.pool_completed.is_empty() {
             while let Some(entry) = self.pool_completed.pop() {
                 entries.notify(entry);
             }
         }
+    }
+
+    fn poll_entries(&mut self, entries: &mut OutEntries) -> bool {
+        self.poll_blocking(entries);
 
         let mut cqueue = self.inner.completion();
         cqueue.sync();
@@ -240,13 +244,13 @@ impl Driver {
                 self.push_raw(entry.user_data(user_data as _), entries)?;
                 Poll::Pending
             }
-            OpEntry::Blocking => {
+            OpEntry::Blocking => loop {
                 if self.push_blocking(user_data)? {
-                    Poll::Pending
+                    break Poll::Pending;
                 } else {
-                    Poll::Ready(Err(io::Error::from_raw_os_error(libc::EBUSY)))
+                    self.poll_blocking(entries);
                 }
-            }
+            },
         }
     }