Trying to resolve borrow mut error

Author: tiif

src/shims/unix/linux/epoll.rs

@@ -422,6 +422,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             } else {
                 // Blocking
                 let duration = Duration::from_millis(timeout.into());
+                drop(ready_list);
                 this.block_thread(
                     BlockReason::Epoll,
                     Some((TimeoutClock::Monotonic, TimeoutAnchor::Relative, duration)),
@@ -437,14 +438,18 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                             Ok(())
                         }
                         @timeout = |this| {
+                            // No notification after blocking timeout.
                             this.write_scalar(Scalar::from_i32(0), &dest)?;
                             Ok(())
                         }
                     ),
                 );
             }
         } else {
-            // Non-blocking with notification returned.
+            // Immediately return epoll notification without blocking.
+
+            // Attempt to prevent epfd.borrow_mut in blocking_epoll_callback causing ICE.
+            drop(ready_list);
             this.blocking_epoll_callback(epfd_value, weak_epfd, &dest, &event)?;
             return Ok(());
         }
@@ -463,15 +468,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let this = self.eval_context_mut();
 
         let Some(epfd) = weak_epfd.upgrade() else {
-            throw_unsup_format!("epoll file descriptor {epfd_value} is closed while blocking.")
+            throw_unsup_format!("epoll FD {epfd_value} is closed while blocking.")
         };
 
-        let mut binding = epfd.borrow_mut();
-        let epoll_file_description = &mut binding
-            .downcast_mut::<Epoll>()
-            .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_wait`"))?;
+        //TODO: What if, there is another thread that make changes to the global fd table here?
+        // For example close the current epfd, then insert a new one inside?
 
-        let binding = epoll_file_description.get_ready_list();
+        let binding = epfd.borrow_mut().downcast_mut::<Epoll>().unwrap().get_ready_list();
         let mut ready_list = binding.borrow_mut();
         let mut num_of_events: i32 = 0;
         let mut array_iter = this.project_array_fields(event)?;