comment

crates/polars-io/src/pl_async.rs

@@ -231,16 +231,16 @@ impl RuntimeManager {
         Self { rt }
     }
 
-    /// Keep track of rayon threads that drive the runtime. Every thread
-    /// only allows a single runtime. If this thread calls block_on and this
-    /// rayon thread is already driving an async execution we must start a new thread
-    /// otherwise we panic. This can happen when we parallelize reads over 100s of files.
+    /// `block_on` variant that can be entered multiple times. Rayon worker threads
+    /// can sometimes do this due to work-stealing.
+    ///
+    /// # Safety
+    /// The tokio runtime flavor is multi-threaded.
     pub fn block_on_potential_spawn<F>(&'static self, future: F) -> F::Output
     where
         F: Future + Send,
         F::Output: Send,
     {
-        // Safety: The tokio runtime flavor is multi-threaded
         tokio::task::block_in_place(|| self.rt.block_on(future))
     }