From 8f81e0814bd121683ebdfa21b494d1b77fb36403 Mon Sep 17 00:00:00 2001
From: Alice Ryhl <aliceryhl@google.com>
Date: Wed, 29 Apr 2026 07:26:57 +0200
Subject: [PATCH] time: avoid stack overflow in runtime constructor (#8093)

---
 tokio/src/runtime/time/wheel/mod.rs     | 8 ++++++--
 tokio/src/runtime/time_alt/wheel/mod.rs | 8 +++++---
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/tokio/src/runtime/time/wheel/mod.rs b/tokio/src/runtime/time/wheel/mod.rs
index c0c51ef74..a58954c52 100644
--- a/tokio/src/runtime/time/wheel/mod.rs
+++ b/tokio/src/runtime/time/wheel/mod.rs
@@ -5,7 +5,7 @@ mod level;
 pub(crate) use self::level::Expiration;
 use self::level::Level;
 
-use std::{array, ptr::NonNull};
+use std::ptr::NonNull;
 
 use super::entry::STATE_DEREGISTERED;
 use super::EntryList;
@@ -50,9 +50,13 @@ pub(super) const MAX_DURATION: u64 = (1 << (6 * NUM_LEVELS)) - 1;
 impl Wheel {
     /// Creates a new timing wheel.
     pub(crate) fn new() -> Wheel {
+        let mut levels = Vec::with_capacity(NUM_LEVELS);
+        for i in 0..NUM_LEVELS {
+            levels.push(Level::new(i));
+        }
         Wheel {
             elapsed: 0,
-            levels: Box::new(array::from_fn(Level::new)),
+            levels: levels.into_boxed_slice().try_into().unwrap(),
             pending: EntryList::new(),
         }
     }
diff --git a/tokio/src/runtime/time_alt/wheel/mod.rs b/tokio/src/runtime/time_alt/wheel/mod.rs
index 324704e9c..a17ed5b85 100644
--- a/tokio/src/runtime/time_alt/wheel/mod.rs
+++ b/tokio/src/runtime/time_alt/wheel/mod.rs
@@ -5,8 +5,6 @@ use self::level::Level;
 use super::cancellation_queue::Sender;
 use super::{EntryHandle, EntryList, WakeQueue};
 
-use std::array;
-
 /// Hashed timing wheel implementation.
 ///
 /// See [`Driver`] documentation for some implementation notes.
@@ -41,9 +39,13 @@ pub(super) const MAX_DURATION: u64 = (1 << (6 * NUM_LEVELS)) - 1;
 impl Wheel {
     /// Creates a new timing wheel.
     pub(crate) fn new() -> Wheel {
+        let mut levels = Vec::with_capacity(NUM_LEVELS);
+        for i in 0..NUM_LEVELS {
+            levels.push(Level::new(i));
+        }
         Wheel {
             elapsed: 0,
-            levels: Box::new(array::from_fn(Level::new)),
+            levels: levels.into_boxed_slice().try_into().unwrap(),
         }
     }