From b6f30cae9a504aacb71c14aa035e2cfdadbfa17a Mon Sep 17 00:00:00 2001
From: Mattia Pitossi <mattiapitossi@gmail.com>
Date: Mon, 13 Jul 2026 13:33:23 +0200
Subject: [PATCH] rt: flush CQE in case of CQE overflow (#8277)

---
 tokio/src/runtime/io/driver.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tokio/src/runtime/io/driver.rs b/tokio/src/runtime/io/driver.rs
index ab7c931df..5bcdecbf6 100644
--- a/tokio/src/runtime/io/driver.rs
+++ b/tokio/src/runtime/io/driver.rs
@@ -233,6 +233,18 @@ impl Driver {
             let mut guard = handle.get_uring().lock();
             let ctx = &mut *guard;
             ctx.dispatch_completions();
+
+            // There might be some cases where the CQ overflows, so we need to flush
+            // the remaining buffered CQEs.
+            while ctx
+                .uring
+                .as_mut()
+                .is_some_and(|uring| uring.submission().cq_overflow())
+            {
+                ctx.submit()
+                    .expect("failed to flush io_uring completion queue overflow");
+                ctx.dispatch_completions();
+            }
         }
 
         handle.metrics.incr_ready_count_by(ready_count);