1 files changed, 80 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/util/try_lock.rs b/third_party/rust/tokio/src/util/try_lock.rs
new file mode 100644
index 0000000000..8b0edb4a87
--- /dev/null
+++ b/third_party/rust/tokio/src/util/try_lock.rs
@@ -0,0 +1,80 @@
+use crate::loom::sync::atomic::AtomicBool;
+
+use std::cell::UnsafeCell;
+use std::marker::PhantomData;
+use std::ops::{Deref, DerefMut};
+use std::sync::atomic::Ordering::SeqCst;
+
+pub(crate) struct TryLock<T> {
+    locked: AtomicBool,
+    data: UnsafeCell<T>,
+}
+
+pub(crate) struct LockGuard<'a, T> {
+    lock: &'a TryLock<T>,
+    _p: PhantomData<std::rc::Rc<()>>,
+}
+
+unsafe impl<T: Send> Send for TryLock<T> {}
+unsafe impl<T: Send> Sync for TryLock<T> {}
+
+unsafe impl<T: Sync> Sync for LockGuard<'_, T> {}
+
+macro_rules! new {
+    ($data:ident) => {
+        TryLock {
+            locked: AtomicBool::new(false),
+            data: UnsafeCell::new($data),
+        }
+    };
+}
+
+impl<T> TryLock<T> {
+    #[cfg(not(loom))]
+    /// Create a new `TryLock`
+    pub(crate) const fn new(data: T) -> TryLock<T> {
+        new!(data)
+    }
+
+    #[cfg(loom)]
+    /// Create a new `TryLock`
+    pub(crate) fn new(data: T) -> TryLock<T> {
+        new!(data)
+    }
+
+    /// Attempt to acquire lock
+    pub(crate) fn try_lock(&self) -> Option<LockGuard<'_, T>> {
+        if self
+            .locked
+            .compare_exchange(false, true, SeqCst, SeqCst)
+            .is_err()
+        {
+            return None;
+        }
+
+        Some(LockGuard {
+            lock: self,
+            _p: PhantomData,
+        })
+    }
+}
+
+impl<T> Deref for LockGuard<'_, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.lock.data.get() }
+    }
+}
+
+impl<T> DerefMut for LockGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.lock.data.get() }
+    }
+}
+
+impl<T> Drop for LockGuard<'_, T> {
+    fn drop(&mut self) {
+        self.lock.locked.store(false, SeqCst);
+    }
+}