Implement EINTR for anything using wait_queue

src/sync/wait_map.rs

@@ -27,6 +27,7 @@ impl<K, V> WaitMap<K, V> where K: Clone + Ord {
             if let Some(value) = self.receive_nonblock(key) {
                 return value;
             }
+            //TODO: use false from wait condition to indicate EINTR
             let _ = self.condition.wait();
         }
     }

src/sync/wait_queue.rs

@@ -28,20 +28,22 @@ impl<T> WaitQueue<T> {
         self.inner.lock().is_empty()
     }
 
-    pub fn receive(&self) -> T {
+    pub fn receive(&self) -> Option<T> {
         loop {
             if let Some(value) = self.inner.lock().pop_front() {
-                return value;
+                return Some(value);
+            }
+            if ! self.condition.wait() {
+                return None;
             }
-            let _ = self.condition.wait();
         }
     }
 
-    pub fn receive_into(&self, buf: &mut [T], block: bool) -> usize {
+    pub fn receive_into(&self, buf: &mut [T], block: bool) -> Option<usize> {
         let mut i = 0;
 
         if i < buf.len() && block {
-            buf[i] = self.receive();
+            buf[i] = self.receive()?;
             i += 1;
         }
 
@@ -57,7 +59,7 @@ impl<T> WaitQueue<T> {
             }
         }
 
-        i
+        Some(i)
     }
 
     pub fn send(&self, value: T) -> usize {