Refactor the logic

src/shims/unix/linux/epoll.rs

@@ -431,35 +431,42 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let mut num_of_events: i32 = 0;
         let mut array_iter = this.project_array_fields(&event)?;
 
-        while let Some(des) = array_iter.next(this)?
-            && !ready_list.is_empty()
-        {
-            let mut entry_written = false;
-            // Fetch an event from the ready list.
-            while !entry_written {
-                if let Some((epoll_key, epoll_return)) = ready_list.pop_first() {
-                    // If the file description is fully close, the entry for corresponding FdID in the
-                    // global epoll event interest table would be empty.
-                    if this.machine.epoll_interests.get_epoll_interest(epoll_key.0).is_some() {
-                        // Return notification to the caller if the file description is not fully closed.
-                        this.write_int_fields_named(
-                            &[
-                                ("events", epoll_return.events.into()),
-                                ("u64", epoll_return.data.into()),
-                            ],
-                            &des.1,
-                        )?;
-                        num_of_events = num_of_events.checked_add(1).unwrap();
-                        entry_written = true;
-                    }
-                } else {
-                    break;
-                }
+        while let Some(des) = array_iter.next(this)? {
+            if let Some(epoll_event_instance) = this.ready_list_next(&mut ready_list) {
+                this.write_int_fields_named(
+                    &[
+                        ("events", epoll_event_instance.events.into()),
+                        ("u64", epoll_event_instance.data.into()),
+                    ],
+                    &des.1,
+                )?;
+                num_of_events = num_of_events.checked_add(1).unwrap();
+            } else {
+                break;
             }
         }
         Ok(Scalar::from_i32(num_of_events))
     }
 
+    /// This function takes in ready list and returns EpollEventInstance with file descriptions
+    /// that are not closed.
+    fn ready_list_next(
+        &self,
+        ready_list: &mut BTreeMap<(FdId, i32), EpollEventInstance>,
+    ) -> Option<EpollEventInstance> {
+        let this = self.eval_context_ref();
+        while let Some((epoll_key, epoll_event_instance)) = ready_list.pop_first() {
+            // This ensures that we only return events that we are interested. The FD might have been closed since
+            // the event was generated, in which case we are not interested anymore.
+            if this.machine.epoll_interests.get_epoll_interest(epoll_key.0).is_some() {
+                // If the file description is fully close, the entry for corresponding FdID in the
+                // global epoll event interest table would be empty.
+                return Some(epoll_event_instance);
+            }
+        }
+        return None;
+    }
+
     /// For a specific file description, get its ready events and update the corresponding ready
     /// list. This function should be called whenever an event causes more bytes or an EOF to become
     /// newly readable from an FD, and whenever more bytes can be written to an FD or no more future