sync: add a rwlock() method to owned RwLock guards

Adds a `rwlock()` method returning a reference to the original `Arc<RwLock>` to the `Owned*` guards.

Author: r3v2d0g

tokio/src/sync/rwlock/owned_read_guard.rs

@@ -138,6 +138,32 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockReadGuard<T, U> {
             resource_span: this.resource_span,
         })
     }
+
+    /// Returns a reference to the original `Arc<RwLock>`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Arc;
+    /// use tokio::sync::{RwLock, OwnedRwLockReadGuard};
+    ///
+    /// #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    /// struct Foo(u32);
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let lock = Arc::new(RwLock::new(Foo(1)));
+    ///
+    /// let guard = lock.clone().read_owned().await;
+    /// assert!(Arc::ptr_eq(&lock, guard.rwlock()));
+    ///
+    /// let guard = OwnedRwLockReadGuard::map(guard, |f| &f.0);
+    /// assert!(Arc::ptr_eq(&lock, guard.rwlock()));
+    /// # }
+    /// ```
+    pub fn rwlock(&self) -> &Arc<RwLock<T>> {
+        &self.lock
+    }
 }
 
 impl<T: ?Sized, U: ?Sized> ops::Deref for OwnedRwLockReadGuard<T, U> {

tokio/src/sync/rwlock/owned_write_guard.rs

@@ -390,6 +390,26 @@ impl<T: ?Sized> OwnedRwLockWriteGuard<T> {
 
         guard
     }
+
+    /// Returns a reference to the original `Arc<RwLock>`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Arc;
+    /// use tokio::sync::RwLock;
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let lock = Arc::new(RwLock::new(1));
+    ///
+    /// let guard = lock.clone().write_owned().await;
+    /// assert!(Arc::ptr_eq(&lock, guard.rwlock()));
+    /// # }
+    /// ```
+    pub fn rwlock(&self) -> &Arc<RwLock<T>> {
+        &self.lock
+    }
 }
 
 impl<T: ?Sized> ops::Deref for OwnedRwLockWriteGuard<T> {

tokio/src/sync/rwlock/owned_write_guard_mapped.rs

@@ -155,6 +155,27 @@ impl<T: ?Sized, U: ?Sized> OwnedRwLockMappedWriteGuard<T, U> {
             resource_span: this.resource_span,
         })
     }
+
+    /// Returns a reference to the original `Arc<RwLock>`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::sync::Arc;
+    /// use tokio::sync::{RwLock, OwnedRwLockMappedWriteGuard};
+    ///
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let lock = Arc::new(RwLock::new(1));
+    ///
+    /// let guard = lock.clone().write_owned().await;
+    /// let guard = OwnedRwLockMappedWriteGuard::map(guard, |x| x);
+    /// assert!(Arc::ptr_eq(&lock, guard.rwlock()));
+    /// # }
+    /// ```
+    pub fn rwlock(&self) -> &Arc<RwLock<T>> {
+        &self.lock
+    }
 }
 
 impl<T: ?Sized, U: ?Sized> ops::Deref for OwnedRwLockMappedWriteGuard<T, U> {