cros_async: Make block_on a top-level function

This doesn't really have anything to do with synchronization so move it
into its own module and export it as a top-level function.

BUG=b:179755651
TEST=cargo test

Change-Id: Icb733c36ee1d4cebcb445e47289c92b9b77a278b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2987583
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-by: Noah Gold <nkgold@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Chirantan Ekbote <chirantan@chromium.org>

cros_async/src/blocking.rs

@@ -0,0 +1,7 @@
+// Copyright 2021 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+mod block_on;
+
+pub use block_on::*;

cros_async/src/lib.rs

@@ -58,6 +58,7 @@
 //! See the docs for `IoSourceExt` if support for kernels <5.4 is required. Focus on `UringSource` if
 //! all systems have support for io_uring.
 
+mod blocking;
 mod complete;
 mod event;
 mod executor;
@@ -73,6 +74,7 @@ mod uring_executor;
 mod uring_source;
 mod waker;
 
+pub use blocking::block_on;
 pub use event::EventAsync;
 pub use executor::Executor;
 pub use fd_executor::FdExecutor;

cros_async/src/sync.rs

@@ -2,13 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-mod blocking;
 mod cv;
 mod mu;
 mod spin;
 mod waiter;
 
-pub use blocking::block_on;
 pub use cv::Condvar;
 pub use mu::Mutex;
 pub use spin::SpinLock;

cros_async/src/sync/cv.rs

@@ -28,7 +28,10 @@ const HAS_WAITERS: usize = 1 << 1;
 /// use std::thread;
 /// use std::sync::mpsc::channel;
 ///
-/// use cros_async::sync::{block_on, Condvar, Mutex};
+/// use cros_async::{
+///     block_on,
+///     sync::{Condvar, Mutex},
+/// };
 ///
 /// const N: usize = 13;
 ///
@@ -93,7 +96,10 @@ impl Condvar {
     /// # use std::sync::Arc;
     /// # use std::thread;
     ///
-    /// # use cros_async::sync::{block_on, Condvar, Mutex};
+    /// # use cros_async::{
+    /// #     block_on,
+    /// #     sync::{Condvar, Mutex},
+    /// # };
     ///
     /// # let mu = Arc::new(Mutex::new(false));
     /// # let cv = Arc::new(Condvar::new());
@@ -458,7 +464,7 @@ mod test {
     use futures_executor::{LocalPool, LocalSpawner, ThreadPool};
     use futures_util::task::LocalSpawnExt;
 
-    use crate::sync::{block_on, Mutex};
+    use crate::{block_on, sync::Mutex};
 
     // Dummy waker used when we want to manually drive futures.
     struct TestWaker;

cros_async/src/sync/mu.rs

@@ -651,7 +651,7 @@ fn cancel_waiter(raw: usize, waiter: &Waiter, wake_next: bool) {
 /// use std::thread;
 /// use std::sync::mpsc::channel;
 ///
-/// use cros_async::sync::{block_on, Mutex};
+/// use cros_async::{block_on, sync::Mutex};
 ///
 /// const N: usize = 10;
 ///
@@ -899,7 +899,10 @@ mod test {
     use futures_executor::{LocalPool, ThreadPool};
     use futures_util::task::LocalSpawnExt;
 
-    use crate::sync::{block_on, Condvar, SpinLock};
+    use crate::{
+        block_on,
+        sync::{Condvar, SpinLock},
+    };
 
     #[derive(Debug, Eq, PartialEq)]
     struct NonCopy(u32);