rt: remove a reference to internal time handle (#5107)

This patch removes a handle to the internal runtime driver handle held
by the runtime. This is another step towards reducing the number of Arc
refs across the runtime internals. Specifically, this change is part of
an effort to remove an Arc in the time driver itself.

tokio/src/runtime/driver.rs

@@ -58,16 +58,16 @@ impl Driver {
         ))
     }
 
-    pub(crate) fn park(&mut self) {
-        self.inner.park()
+    pub(crate) fn park(&mut self, handle: &Handle) {
+        self.inner.park(handle)
     }
 
-    pub(crate) fn park_timeout(&mut self, duration: Duration) {
-        self.inner.park_timeout(duration)
+    pub(crate) fn park_timeout(&mut self, handle: &Handle, duration: Duration) {
+        self.inner.park_timeout(handle, duration)
     }
 
-    pub(crate) fn shutdown(&mut self) {
-        self.inner.shutdown()
+    pub(crate) fn shutdown(&mut self, handle: &Handle) {
+        self.inner.shutdown(handle)
     }
 }
 
@@ -80,6 +80,18 @@ impl Handle {
 
         self.io.unpark();
     }
+
+    cfg_time! {
+        /// Returns a reference to the time driver handle.
+        ///
+        /// Panics if no time driver is present.
+        #[track_caller]
+        pub(crate) fn time(&self) -> &crate::runtime::time::Handle {
+            self.time
+                .as_ref()
+                .expect("A Tokio 1.x context was found, but timers are disabled. Call `enable_time` on the runtime builder to enable timers.")
+        }
+    }
 }
 
 // ===== io driver =====
@@ -121,30 +133,21 @@ cfg_io_driver! {
     }
 
     impl IoStack {
-        /*
-        pub(crate) fn handle(&self) -> IoHandle {
-            match self {
-                IoStack::Enabled(v) => IoHandle::Enabled(v.handle()),
-                IoStack::Disabled(v) => IoHandle::Disabled(v.unpark()),
-            }
-        }]
-        */
-
-        pub(crate) fn park(&mut self) {
+        pub(crate) fn park(&mut self, _handle: &Handle) {
             match self {
                 IoStack::Enabled(v) => v.park(),
                 IoStack::Disabled(v) => v.park(),
             }
         }
 
-        pub(crate) fn park_timeout(&mut self, duration: Duration) {
+        pub(crate) fn park_timeout(&mut self, _handle: &Handle, duration: Duration) {
             match self {
                 IoStack::Enabled(v) => v.park_timeout(duration),
                 IoStack::Disabled(v) => v.park_timeout(duration),
             }
         }
 
-        pub(crate) fn shutdown(&mut self) {
+        pub(crate) fn shutdown(&mut self, _handle: &Handle) {
             match self {
                 IoStack::Enabled(v) => v.shutdown(),
                 IoStack::Disabled(v) => v.shutdown(),
@@ -181,12 +184,28 @@ cfg_io_driver! {
 
 cfg_not_io_driver! {
     pub(crate) type IoHandle = UnparkThread;
-    pub(crate) type IoStack = ParkThread;
+
+    #[derive(Debug)]
+    pub(crate) struct IoStack(ParkThread);
 
     fn create_io_stack(_enabled: bool) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
         let park_thread = ParkThread::new();
         let unpark_thread = park_thread.unpark();
-        Ok((park_thread, unpark_thread, Default::default()))
+        Ok((IoStack(park_thread), unpark_thread, Default::default()))
+    }
+
+    impl IoStack {
+        pub(crate) fn park(&mut self, _handle: &Handle) {
+            self.0.park();
+        }
+
+        pub(crate) fn park_timeout(&mut self, _handle: &Handle, duration: Duration) {
+            self.0.park_timeout(duration);
+        }
+
+        pub(crate) fn shutdown(&mut self, _handle: &Handle) {
+            self.0.shutdown();
+        }
     }
 }
 
@@ -249,7 +268,6 @@ cfg_time! {
     pub(crate) enum TimeDriver {
         Enabled {
             driver: crate::runtime::time::Driver,
-            handle: crate::runtime::time::Handle,
         },
         Disabled(IoStack),
     }
@@ -269,31 +287,31 @@ cfg_time! {
         if enable {
             let (driver, handle) = crate::runtime::time::Driver::new(io_stack, clock);
 
-            (TimeDriver::Enabled { driver, handle: handle.clone() }, Some(handle))
+            (TimeDriver::Enabled { driver }, Some(handle))
         } else {
             (TimeDriver::Disabled(io_stack), None)
         }
     }
 
     impl TimeDriver {
-        pub(crate) fn park(&mut self) {
+        pub(crate) fn park(&mut self, handle: &Handle) {
             match self {
-                TimeDriver::Enabled { driver, handle } => driver.park(handle),
-                TimeDriver::Disabled(v) => v.park(),
+                TimeDriver::Enabled { driver, .. } => driver.park(handle),
+                TimeDriver::Disabled(v) => v.park(handle),
             }
         }
 
-        pub(crate) fn park_timeout(&mut self, duration: Duration) {
+        pub(crate) fn park_timeout(&mut self, handle: &Handle, duration: Duration) {
             match self {
-                TimeDriver::Enabled { driver, handle } => driver.park_timeout(handle, duration),
-                TimeDriver::Disabled(v) => v.park_timeout(duration),
+                TimeDriver::Enabled { driver } => driver.park_timeout(handle, duration),
+                TimeDriver::Disabled(v) => v.park_timeout(handle, duration),
             }
         }
 
-        pub(crate) fn shutdown(&mut self) {
+        pub(crate) fn shutdown(&mut self, handle: &Handle) {
             match self {
-                TimeDriver::Enabled { driver, handle } => driver.shutdown(handle),
-                TimeDriver::Disabled(v) => v.shutdown(),
+                TimeDriver::Enabled { driver } => driver.shutdown(handle),
+                TimeDriver::Disabled(v) => v.shutdown(handle),
             }
         }
     }

tokio/src/runtime/scheduler/current_thread.rs

@@ -247,7 +247,7 @@ impl Drop for CurrentThread {
 
             // Shutdown the resource drivers
             if let Some(driver) = core.driver.as_mut() {
-                driver.shutdown();
+                driver.shutdown(&self.handle.driver);
             }
 
             (core, ())
@@ -314,7 +314,7 @@ impl Context {
             core.metrics.submit(&self.handle.shared.worker_metrics);
 
             let (c, _) = self.enter(core, || {
-                driver.park();
+                driver.park(&self.handle.driver);
             });
 
             core = c;
@@ -339,7 +339,7 @@ impl Context {
 
         core.metrics.submit(&self.handle.shared.worker_metrics);
         let (mut core, _) = self.enter(core, || {
-            driver.park_timeout(Duration::from_millis(0));
+            driver.park_timeout(&self.handle.driver, Duration::from_millis(0));
         });
 
         core.driver = Some(driver);

tokio/src/runtime/scheduler/mod.rs

@@ -43,10 +43,7 @@ impl Handle {
     cfg_time! {
         #[track_caller]
         pub(crate) fn time(&self) -> &crate::runtime::time::Handle {
-            self.driver()
-                .time
-                .as_ref()
-                .expect("A Tokio 1.x context was found, but timers are disabled. Call `enable_time` on the runtime builder to enable timers.")
+            self.driver().time()
         }
 
         cfg_test_util! {

tokio/src/runtime/scheduler/multi_thread/park.rs

@@ -64,21 +64,21 @@ impl Parker {
         }
     }
 
-    pub(crate) fn park(&mut self) {
-        self.inner.park();
+    pub(crate) fn park(&mut self, handle: &driver::Handle) {
+        self.inner.park(handle);
     }
 
-    pub(crate) fn park_timeout(&mut self, duration: Duration) {
+    pub(crate) fn park_timeout(&mut self, handle: &driver::Handle, duration: Duration) {
         // Only parking with zero is supported...
         assert_eq!(duration, Duration::from_millis(0));
 
         if let Some(mut driver) = self.inner.shared.driver.try_lock() {
-            driver.park_timeout(duration)
+            driver.park_timeout(handle, duration)
         }
     }
 
-    pub(crate) fn shutdown(&mut self) {
-        self.inner.shutdown();
+    pub(crate) fn shutdown(&mut self, handle: &driver::Handle) {
+        self.inner.shutdown(handle);
     }
 }
 
@@ -103,7 +103,7 @@ impl Unparker {
 
 impl Inner {
     /// Parks the current thread for at most `dur`.
-    fn park(&self) {
+    fn park(&self, handle: &driver::Handle) {
         for _ in 0..3 {
             // If we were previously notified then we consume this notification and
             // return quickly.
@@ -119,7 +119,7 @@ impl Inner {
         }
 
         if let Some(mut driver) = self.shared.driver.try_lock() {
-            self.park_driver(&mut driver);
+            self.park_driver(&mut driver, handle);
         } else {
             self.park_condvar();
         }
@@ -165,7 +165,7 @@ impl Inner {
         }
     }
 
-    fn park_driver(&self, driver: &mut Driver) {
+    fn park_driver(&self, driver: &mut Driver, handle: &driver::Handle) {
         match self
             .state
             .compare_exchange(EMPTY, PARKED_DRIVER, SeqCst, SeqCst)
@@ -186,7 +186,7 @@ impl Inner {
             Err(actual) => panic!("inconsistent park state; actual = {}", actual),
         }
 
-        driver.park();
+        driver.park(handle);
 
         match self.state.swap(EMPTY, SeqCst) {
             NOTIFIED => {}      // got a notification, hurray!
@@ -227,9 +227,9 @@ impl Inner {
         self.condvar.notify_one()
     }
 
-    fn shutdown(&self) {
+    fn shutdown(&self, handle: &driver::Handle) {
         if let Some(mut driver) = self.shared.driver.try_lock() {
-            driver.shutdown();
+            driver.shutdown(handle);
         }
 
         self.condvar.notify_all();

tokio/src/runtime/scheduler/multi_thread/worker.rs

@@ -522,9 +522,9 @@ impl Context {
 
         // Park thread
         if let Some(timeout) = duration {
-            park.park_timeout(timeout);
+            park.park_timeout(&self.worker.handle.driver, timeout);
         } else {
-            park.park();
+            park.park(&self.worker.handle.driver);
         }
 
         // Remove `core` from context
@@ -687,14 +687,14 @@ impl Core {
     }
 
     /// Shuts down the core.
-    fn shutdown(&mut self) {
+    fn shutdown(&mut self, handle: &Handle) {
         // Take the core
         let mut park = self.park.take().expect("park missing");
 
         // Drain the queue
         while self.next_local_task().is_some() {}
 
-        park.shutdown();
+        park.shutdown(&handle.driver);
     }
 }
 
@@ -829,7 +829,7 @@ impl Handle {
         debug_assert!(self.shared.owned.is_empty());
 
         for mut core in cores.drain(..) {
-            core.shutdown();
+            core.shutdown(self);
         }
 
         // Drain the injection queue