From 98e642d23477d1af8d7a62d41d9907e567241a71 Mon Sep 17 00:00:00 2001
From: Carl Lerche <me@carllerche.com>
Date: Wed, 14 Sep 2022 15:47:41 -0700
Subject: [PATCH] rt: remove driver drop implementations (#5014)

Currently, drivers are responsible for clean up when they are dropped.
This is possible today because each driver struct holds a reference to
its internal handle.

As part of an effort to decouple drivers from their handles, this patch
removes the drop implementations for the time and IO driver in favor of
having the scheduler explicitly call `shutdown()` as part of its
shutdown process. The scheduler will hold a reference to both the driver
and the driver handles, so in the future, it will be able to pass in the
driver handles as part of the shutdown process.
---
 tokio/src/runtime/driver.rs                   | 27 +++++--------------
 tokio/src/runtime/io/mod.rs                   |  6 -----
 tokio/src/runtime/scheduler/current_thread.rs |  5 ++++
 3 files changed, 11 insertions(+), 27 deletions(-)

diff --git a/tokio/src/runtime/driver.rs b/tokio/src/runtime/driver.rs
index 1d90c7945..7715d7030 100644
--- a/tokio/src/runtime/driver.rs
+++ b/tokio/src/runtime/driver.rs
@@ -70,7 +70,6 @@ cfg_io_driver! {
             }
         }
 
-        #[cfg_attr(not(feature = "rt-multi-thread"), allow(dead_code))] // some features use this
         pub(crate) fn shutdown(&mut self) {
             match self {
                 IoStack::Enabled(v) => v.shutdown(),
@@ -230,21 +229,10 @@ cfg_time! {
             }
         }
 
-        // TODO: tokio-rs/tokio#4990, should the `current_thread` scheduler call this?
-        cfg_rt_multi_thread! {
-            pub(crate) fn shutdown(&mut self) {
-                match self {
-                    TimeDriver::Enabled { driver, handle } => driver.shutdown(handle),
-                    TimeDriver::Disabled(v) => v.shutdown(),
-                }
-            }
-        }
-    }
-
-    impl Drop for TimeDriver {
-        fn drop(&mut self) {
-            if let TimeDriver::Enabled { driver, handle } = self {
-                driver.shutdown(handle);
+        pub(crate) fn shutdown(&mut self) {
+            match self {
+                TimeDriver::Enabled { driver, handle } => driver.shutdown(handle),
+                TimeDriver::Disabled(v) => v.shutdown(),
             }
         }
     }
@@ -334,10 +322,7 @@ impl Driver {
         self.inner.park_timeout(duration)
     }
 
-    // TODO: tokio-rs/tokio#4990, should the `current_thread` scheduler call this?
-    cfg_rt_multi_thread! {
-        pub(crate) fn shutdown(&mut self) {
-            self.inner.shutdown()
-        }
+    pub(crate) fn shutdown(&mut self) {
+        self.inner.shutdown()
     }
 }
diff --git a/tokio/src/runtime/io/mod.rs b/tokio/src/runtime/io/mod.rs
index 22d84cbb6..8a8367477 100644
--- a/tokio/src/runtime/io/mod.rs
+++ b/tokio/src/runtime/io/mod.rs
@@ -230,12 +230,6 @@ impl Driver {
     }
 }
 
-impl Drop for Driver {
-    fn drop(&mut self) {
-        self.shutdown();
-    }
-}
-
 impl fmt::Debug for Driver {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "Driver")
diff --git a/tokio/src/runtime/scheduler/current_thread.rs b/tokio/src/runtime/scheduler/current_thread.rs
index b705c786d..c57fddd09 100644
--- a/tokio/src/runtime/scheduler/current_thread.rs
+++ b/tokio/src/runtime/scheduler/current_thread.rs
@@ -236,6 +236,11 @@ impl Drop for CurrentThread {
             // Submit metrics
             core.metrics.submit(&core.spawner.shared.worker_metrics);
 
+            // Shutdown the resource drivers
+            if let Some(driver) = core.driver.as_mut() {
+                driver.shutdown();
+            }
+
             (core, ())
         });
     }