diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d73eb5959..38f650804 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -268,26 +268,42 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        target:
-          - i686-unknown-linux-gnu
-          - arm-unknown-linux-gnueabihf
-          - armv7-unknown-linux-gnueabihf
-          - aarch64-unknown-linux-gnu
+        include:
+          - target: i686-unknown-linux-gnu
+          - target: arm-unknown-linux-gnueabihf
+          - target: armv7-unknown-linux-gnueabihf
+          - target: aarch64-unknown-linux-gnu
+
+          # Run a platform without AtomicU64 and no const Mutex::new
+          - target: arm-unknown-linux-gnueabihf
+            rustflags: --cfg tokio_no_const_mutex_new
     steps:
       - uses: actions/checkout@v3
-      - name: Install Rust ${{ env.rust_stable }}
+      - name: Install Rust stable
         uses: actions-rs/toolchain@v1
         with:
           toolchain: ${{ env.rust_stable }}
           target: ${{ matrix.target }}
           override: true
+      # First run with all features (including parking_lot)
       - uses: actions-rs/cargo@v1
         with:
           use-cross: true
           command: test
           args: -p tokio --all-features --target ${{ matrix.target }} --tests
         env:
-          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_ipv6
+          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_ipv6 ${{ matrix.rustflags }}
+      # Now run without parking_lot
+      - name: Remove `parking_lot` from `full` feature
+        run: sed -i '0,/parking_lot/{/parking_lot/d;}' tokio/Cargo.toml
+      - uses: actions-rs/cargo@v1
+        with:
+          use-cross: true
+          command: test
+          # The `tokio_no_parking_lot` cfg is here to ensure the `sed` above does not silently break.
+          args: -p tokio --features full,test-util --target ${{ matrix.target }} --tests
+        env:
+          RUSTFLAGS: --cfg tokio_unstable -Dwarnings --cfg tokio_no_ipv6 --cfg tokio_no_parking_lot ${{ matrix.rustflags }}
 
   # See https://github.com/tokio-rs/tokio/issues/5187
   no-atomic-u64:
diff --git a/tokio/tests/_require_full.rs b/tokio/tests/_require_full.rs
index a339374fd..4b9698afe 100644
--- a/tokio/tests/_require_full.rs
+++ b/tokio/tests/_require_full.rs
@@ -1,2 +1,8 @@
-#![cfg(not(any(feature = "full", tokio_wasm)))]
+#[cfg(not(any(feature = "full", tokio_wasm)))]
 compile_error!("run main Tokio tests with `--features full`");
+
+// CI sets `--cfg tokio_no_parking_lot` when trying to run tests with
+// `parking_lot` disabled. This check prevents "silent failure" if `parking_lot`
+// accidentally gets enabled.
+#[cfg(all(tokio_no_parking_lot, feature = "parking_lot"))]
+compile_error!("parking_lot feature enabled when it should not be");
diff --git a/tokio/tests/support/panic.rs b/tokio/tests/support/panic.rs
index 7f60c76f0..df2f59d30 100644
--- a/tokio/tests/support/panic.rs
+++ b/tokio/tests/support/panic.rs
@@ -1,9 +1,8 @@
-use parking_lot::{const_mutex, Mutex};
 use std::panic;
-use std::sync::Arc;
+use std::sync::{Arc, Mutex};
 
 pub fn test_panic<Func: FnOnce() + panic::UnwindSafe>(func: Func) -> Option<String> {
-    static PANIC_MUTEX: Mutex<()> = const_mutex(());
+    static PANIC_MUTEX: Mutex<()> = Mutex::new(());
 
     {
         let _guard = PANIC_MUTEX.lock();
@@ -16,6 +15,7 @@ pub fn test_panic<Func: FnOnce() + panic::UnwindSafe>(func: Func) -> Option<Stri
                 let panic_location = panic_info.location().unwrap();
                 panic_file
                     .lock()
+                    .unwrap()
                     .clone_from(&Some(panic_location.file().to_string()));
             }));
         }
@@ -26,7 +26,7 @@ pub fn test_panic<Func: FnOnce() + panic::UnwindSafe>(func: Func) -> Option<Stri
         panic::set_hook(prev_hook);
 
         if result.is_err() {
-            panic_file.lock().clone()
+            panic_file.lock().unwrap().clone()
         } else {
             None
         }
diff --git a/tokio/tests/sync_once_cell.rs b/tokio/tests/sync_once_cell.rs
index 18eaf9382..38dfa7ca0 100644
--- a/tokio/tests/sync_once_cell.rs
+++ b/tokio/tests/sync_once_cell.rs
@@ -4,178 +4,7 @@
 use std::mem;
 use std::ops::Drop;
 use std::sync::atomic::{AtomicU32, Ordering};
-use std::time::Duration;
-use tokio::runtime;
-use tokio::sync::{OnceCell, SetError};
-use tokio::time;
-
-async fn func1() -> u32 {
-    5
-}
-
-async fn func2() -> u32 {
-    time::sleep(Duration::from_millis(1)).await;
-    10
-}
-
-async fn func_err() -> Result<u32, ()> {
-    Err(())
-}
-
-async fn func_ok() -> Result<u32, ()> {
-    Ok(10)
-}
-
-async fn func_panic() -> u32 {
-    time::sleep(Duration::from_millis(1)).await;
-    panic!();
-}
-
-async fn sleep_and_set() -> u32 {
-    // Simulate sleep by pausing time and waiting for another thread to
-    // resume clock when calling `set`, then finding the cell being initialized
-    // by this call
-    time::sleep(Duration::from_millis(2)).await;
-    5
-}
-
-async fn advance_time_and_set(cell: &'static OnceCell<u32>, v: u32) -> Result<(), SetError<u32>> {
-    time::advance(Duration::from_millis(1)).await;
-    cell.set(v)
-}
-
-#[test]
-fn get_or_init() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .start_paused(true)
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
-        let handle2 = rt.spawn(async { ONCE.get_or_init(func2).await });
-
-        time::advance(Duration::from_millis(1)).await;
-        time::resume();
-
-        let result1 = handle1.await.unwrap();
-        let result2 = handle2.await.unwrap();
-
-        assert_eq!(*result1, 5);
-        assert_eq!(*result2, 5);
-    });
-}
-
-#[test]
-fn get_or_init_panic() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        time::pause();
-
-        let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
-        let handle2 = rt.spawn(async { ONCE.get_or_init(func_panic).await });
-
-        time::advance(Duration::from_millis(1)).await;
-
-        let result1 = handle1.await.unwrap();
-        let result2 = handle2.await.unwrap();
-
-        assert_eq!(*result1, 5);
-        assert_eq!(*result2, 5);
-    });
-}
-
-#[test]
-fn set_and_get() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        let _ = rt.spawn(async { ONCE.set(5) }).await;
-        let value = ONCE.get().unwrap();
-        assert_eq!(*value, 5);
-    });
-}
-
-#[test]
-fn get_uninit() {
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-    let uninit = ONCE.get();
-    assert!(uninit.is_none());
-}
-
-#[test]
-fn set_twice() {
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    let first = ONCE.set(5);
-    assert_eq!(first, Ok(()));
-    let second = ONCE.set(6);
-    assert!(second.err().unwrap().is_already_init_err());
-}
-
-#[test]
-fn set_while_initializing() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        time::pause();
-
-        let handle1 = rt.spawn(async { ONCE.get_or_init(sleep_and_set).await });
-        let handle2 = rt.spawn(async { advance_time_and_set(&ONCE, 10).await });
-
-        time::advance(Duration::from_millis(2)).await;
-
-        let result1 = handle1.await.unwrap();
-        let result2 = handle2.await.unwrap();
-
-        assert_eq!(*result1, 5);
-        assert!(result2.err().unwrap().is_initializing_err());
-    });
-}
-
-#[test]
-fn get_or_try_init() {
-    let rt = runtime::Builder::new_current_thread()
-        .enable_time()
-        .start_paused(true)
-        .build()
-        .unwrap();
-
-    static ONCE: OnceCell<u32> = OnceCell::const_new();
-
-    rt.block_on(async {
-        let handle1 = rt.spawn(async { ONCE.get_or_try_init(func_err).await });
-        let handle2 = rt.spawn(async { ONCE.get_or_try_init(func_ok).await });
-
-        time::advance(Duration::from_millis(1)).await;
-        time::resume();
-
-        let result1 = handle1.await.unwrap();
-        assert!(result1.is_err());
-
-        let result2 = handle2.await.unwrap();
-        assert_eq!(*result2.unwrap(), 10);
-    });
-}
+use tokio::sync::OnceCell;
 
 #[test]
 fn drop_cell() {
@@ -272,3 +101,185 @@ fn from() {
     let cell = OnceCell::from(2);
     assert_eq!(*cell.get().unwrap(), 2);
 }
+
+#[cfg(feature = "parking_lot")]
+mod parking_lot {
+    use super::*;
+
+    use tokio::runtime;
+    use tokio::sync::SetError;
+    use tokio::time;
+
+    use std::time::Duration;
+
+    async fn func1() -> u32 {
+        5
+    }
+
+    async fn func2() -> u32 {
+        time::sleep(Duration::from_millis(1)).await;
+        10
+    }
+
+    async fn func_err() -> Result<u32, ()> {
+        Err(())
+    }
+
+    async fn func_ok() -> Result<u32, ()> {
+        Ok(10)
+    }
+
+    async fn func_panic() -> u32 {
+        time::sleep(Duration::from_millis(1)).await;
+        panic!();
+    }
+
+    async fn sleep_and_set() -> u32 {
+        // Simulate sleep by pausing time and waiting for another thread to
+        // resume clock when calling `set`, then finding the cell being initialized
+        // by this call
+        time::sleep(Duration::from_millis(2)).await;
+        5
+    }
+
+    async fn advance_time_and_set(
+        cell: &'static OnceCell<u32>,
+        v: u32,
+    ) -> Result<(), SetError<u32>> {
+        time::advance(Duration::from_millis(1)).await;
+        cell.set(v)
+    }
+
+    #[test]
+    fn get_or_init() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .start_paused(true)
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
+            let handle2 = rt.spawn(async { ONCE.get_or_init(func2).await });
+
+            time::advance(Duration::from_millis(1)).await;
+            time::resume();
+
+            let result1 = handle1.await.unwrap();
+            let result2 = handle2.await.unwrap();
+
+            assert_eq!(*result1, 5);
+            assert_eq!(*result2, 5);
+        });
+    }
+
+    #[test]
+    fn get_or_init_panic() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            time::pause();
+
+            let handle1 = rt.spawn(async { ONCE.get_or_init(func1).await });
+            let handle2 = rt.spawn(async { ONCE.get_or_init(func_panic).await });
+
+            time::advance(Duration::from_millis(1)).await;
+
+            let result1 = handle1.await.unwrap();
+            let result2 = handle2.await.unwrap();
+
+            assert_eq!(*result1, 5);
+            assert_eq!(*result2, 5);
+        });
+    }
+
+    #[test]
+    fn set_and_get() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            let _ = rt.spawn(async { ONCE.set(5) }).await;
+            let value = ONCE.get().unwrap();
+            assert_eq!(*value, 5);
+        });
+    }
+
+    #[test]
+    fn get_uninit() {
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+        let uninit = ONCE.get();
+        assert!(uninit.is_none());
+    }
+
+    #[test]
+    fn set_twice() {
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        let first = ONCE.set(5);
+        assert_eq!(first, Ok(()));
+        let second = ONCE.set(6);
+        assert!(second.err().unwrap().is_already_init_err());
+    }
+
+    #[test]
+    fn set_while_initializing() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            time::pause();
+
+            let handle1 = rt.spawn(async { ONCE.get_or_init(sleep_and_set).await });
+            let handle2 = rt.spawn(async { advance_time_and_set(&ONCE, 10).await });
+
+            time::advance(Duration::from_millis(2)).await;
+
+            let result1 = handle1.await.unwrap();
+            let result2 = handle2.await.unwrap();
+
+            assert_eq!(*result1, 5);
+            assert!(result2.err().unwrap().is_initializing_err());
+        });
+    }
+
+    #[test]
+    fn get_or_try_init() {
+        let rt = runtime::Builder::new_current_thread()
+            .enable_time()
+            .start_paused(true)
+            .build()
+            .unwrap();
+
+        static ONCE: OnceCell<u32> = OnceCell::const_new();
+
+        rt.block_on(async {
+            let handle1 = rt.spawn(async { ONCE.get_or_try_init(func_err).await });
+            let handle2 = rt.spawn(async { ONCE.get_or_try_init(func_ok).await });
+
+            time::advance(Duration::from_millis(1)).await;
+            time::resume();
+
+            let result1 = handle1.await.unwrap();
+            assert!(result1.is_err());
+
+            let result2 = handle2.await.unwrap();
+            assert_eq!(*result2.unwrap(), 10);
+        });
+    }
+}
diff --git a/tokio/tests/task_join_set.rs b/tokio/tests/task_join_set.rs
index 20d492721..b1b6cf966 100644
--- a/tokio/tests/task_join_set.rs
+++ b/tokio/tests/task_join_set.rs
@@ -5,8 +5,6 @@ use tokio::sync::oneshot;
 use tokio::task::JoinSet;
 use tokio::time::Duration;
 
-use futures::future::FutureExt;
-
 fn rt() -> tokio::runtime::Runtime {
     tokio::runtime::Builder::new_current_thread()
         .build()
@@ -156,49 +154,6 @@ fn runtime_gone() {
         .is_cancelled());
 }
 
-// This ensures that `join_next` works correctly when the coop budget is
-// exhausted.
-#[tokio::test(flavor = "current_thread")]
-async fn join_set_coop() {
-    // Large enough to trigger coop.
-    const TASK_NUM: u32 = 1000;
-
-    static SEM: tokio::sync::Semaphore = tokio::sync::Semaphore::const_new(0);
-
-    let mut set = JoinSet::new();
-
-    for _ in 0..TASK_NUM {
-        set.spawn(async {
-            SEM.add_permits(1);
-        });
-    }
-
-    // Wait for all tasks to complete.
-    //
-    // Since this is a `current_thread` runtime, there's no race condition
-    // between the last permit being added and the task completing.
-    let _ = SEM.acquire_many(TASK_NUM).await.unwrap();
-
-    let mut count = 0;
-    let mut coop_count = 0;
-    loop {
-        match set.join_next().now_or_never() {
-            Some(Some(Ok(()))) => {}
-            Some(Some(Err(err))) => panic!("failed: {}", err),
-            None => {
-                coop_count += 1;
-                tokio::task::yield_now().await;
-                continue;
-            }
-            Some(None) => break,
-        }
-
-        count += 1;
-    }
-    assert!(coop_count >= 1);
-    assert_eq!(count, TASK_NUM);
-}
-
 #[tokio::test(start_paused = true)]
 async fn abort_all() {
     let mut set: JoinSet<()> = JoinSet::new();
@@ -228,3 +183,53 @@ async fn abort_all() {
     assert_eq!(count, 10);
     assert_eq!(set.len(), 0);
 }
+
+#[cfg(feature = "parking_lot")]
+mod parking_lot {
+    use super::*;
+
+    use futures::future::FutureExt;
+
+    // This ensures that `join_next` works correctly when the coop budget is
+    // exhausted.
+    #[tokio::test(flavor = "current_thread")]
+    async fn join_set_coop() {
+        // Large enough to trigger coop.
+        const TASK_NUM: u32 = 1000;
+
+        static SEM: tokio::sync::Semaphore = tokio::sync::Semaphore::const_new(0);
+
+        let mut set = JoinSet::new();
+
+        for _ in 0..TASK_NUM {
+            set.spawn(async {
+                SEM.add_permits(1);
+            });
+        }
+
+        // Wait for all tasks to complete.
+        //
+        // Since this is a `current_thread` runtime, there's no race condition
+        // between the last permit being added and the task completing.
+        let _ = SEM.acquire_many(TASK_NUM).await.unwrap();
+
+        let mut count = 0;
+        let mut coop_count = 0;
+        loop {
+            match set.join_next().now_or_never() {
+                Some(Some(Ok(()))) => {}
+                Some(Some(Err(err))) => panic!("failed: {}", err),
+                None => {
+                    coop_count += 1;
+                    tokio::task::yield_now().await;
+                    continue;
+                }
+                Some(None) => break,
+            }
+
+            count += 1;
+        }
+        assert!(coop_count >= 1);
+        assert_eq!(count, TASK_NUM);
+    }
+}