Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 2679 insertions, 0 deletions

diff --git a/third_party/rust/tokio/src/process/kill.rs b/third_party/rust/tokio/src/process/kill.rs
new file mode 100644
index 0000000000..a1f1652281
--- /dev/null
+++ b/third_party/rust/tokio/src/process/kill.rs
@@ -0,0 +1,13 @@
+use std::io;
+
+/// An interface for killing a running process.
+pub(crate) trait Kill {
+    /// Forcefully kills the process.
+    fn kill(&mut self) -> io::Result<()>;
+}
+
+impl<T: Kill> Kill for &mut T {
+    fn kill(&mut self) -> io::Result<()> {
+        (**self).kill()
+    }
+}
diff --git a/third_party/rust/tokio/src/process/mod.rs b/third_party/rust/tokio/src/process/mod.rs
new file mode 100644
index 0000000000..4e1a21dd44
--- /dev/null
+++ b/third_party/rust/tokio/src/process/mod.rs
@@ -0,0 +1,1534 @@
+//! An implementation of asynchronous process management for Tokio.
+//!
+//! This module provides a [`Command`] struct that imitates the interface of the
+//! [`std::process::Command`] type in the standard library, but provides asynchronous versions of
+//! functions that create processes. These functions (`spawn`, `status`, `output` and their
+//! variants) return "future aware" types that interoperate with Tokio. The asynchronous process
+//! support is provided through signal handling on Unix and system APIs on Windows.
+//!
+//! [`std::process::Command`]: std::process::Command
+//!
+//! # Examples
+//!
+//! Here's an example program which will spawn `echo hello world` and then wait
+//! for it complete.
+//!
+//! ```no_run
+//! use tokio::process::Command;
+//!
+//! #[tokio::main]
+//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//!     // The usage is similar as with the standard library's `Command` type
+//!     let mut child = Command::new("echo")
+//!         .arg("hello")
+//!         .arg("world")
+//!         .spawn()
+//!         .expect("failed to spawn");
+//!
+//!     // Await until the command completes
+//!     let status = child.wait().await?;
+//!     println!("the command exited with: {}", status);
+//!     Ok(())
+//! }
+//! ```
+//!
+//! Next, let's take a look at an example where we not only spawn `echo hello
+//! world` but we also capture its output.
+//!
+//! ```no_run
+//! use tokio::process::Command;
+//!
+//! #[tokio::main]
+//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//!     // Like above, but use `output` which returns a future instead of
+//!     // immediately returning the `Child`.
+//!     let output = Command::new("echo").arg("hello").arg("world")
+//!                         .output();
+//!
+//!     let output = output.await?;
+//!
+//!     assert!(output.status.success());
+//!     assert_eq!(output.stdout, b"hello world\n");
+//!     Ok(())
+//! }
+//! ```
+//!
+//! We can also read input line by line.
+//!
+//! ```no_run
+//! use tokio::io::{BufReader, AsyncBufReadExt};
+//! use tokio::process::Command;
+//!
+//! use std::process::Stdio;
+//!
+//! #[tokio::main]
+//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//!     let mut cmd = Command::new("cat");
+//!
+//!     // Specify that we want the command's standard output piped back to us.
+//!     // By default, standard input/output/error will be inherited from the
+//!     // current process (for example, this means that standard input will
+//!     // come from the keyboard and standard output/error will go directly to
+//!     // the terminal if this process is invoked from the command line).
+//!     cmd.stdout(Stdio::piped());
+//!
+//!     let mut child = cmd.spawn()
+//!         .expect("failed to spawn command");
+//!
+//!     let stdout = child.stdout.take()
+//!         .expect("child did not have a handle to stdout");
+//!
+//!     let mut reader = BufReader::new(stdout).lines();
+//!
+//!     // Ensure the child process is spawned in the runtime so it can
+//!     // make progress on its own while we await for any output.
+//!     tokio::spawn(async move {
+//!         let status = child.wait().await
+//!             .expect("child process encountered an error");
+//!
+//!         println!("child status was: {}", status);
+//!     });
+//!
+//!     while let Some(line) = reader.next_line().await? {
+//!         println!("Line: {}", line);
+//!     }
+//!
+//!     Ok(())
+//! }
+//! ```
+//!
+//! Here is another example using `sort` writing into the child process
+//! standard input, capturing the output of the sorted text.
+//!
+//! ```no_run
+//! use tokio::io::AsyncWriteExt;
+//! use tokio::process::Command;
+//!
+//! use std::process::Stdio;
+//!
+//! #[tokio::main]
+//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//!     let mut cmd = Command::new("sort");
+//!
+//!     // Specifying that we want pipe both the output and the input.
+//!     // Similarily to capturing the output, by configuring the pipe
+//!     // to stdin it can now be used as an asynchronous writer.
+//!     cmd.stdout(Stdio::piped());
+//!     cmd.stdin(Stdio::piped());
+//!
+//!     let mut child = cmd.spawn().expect("failed to spawn command");
+//!
+//!     // These are the animals we want to sort
+//!     let animals: &[&str] = &["dog", "bird", "frog", "cat", "fish"];
+//!
+//!     let mut stdin = child
+//!         .stdin
+//!         .take()
+//!         .expect("child did not have a handle to stdin");
+//!
+//!     // Write our animals to the child process
+//!     // Note that the behavior of `sort` is to buffer _all input_ before writing any output.
+//!     // In the general sense, it is recommended to write to the child in a separate task as
+//!     // awaiting its exit (or output) to avoid deadlocks (for example, the child tries to write
+//!     // some output but gets stuck waiting on the parent to read from it, meanwhile the parent
+//!     // is stuck waiting to write its input completely before reading the output).
+//!     stdin
+//!         .write(animals.join("\n").as_bytes())
+//!         .await
+//!         .expect("could not write to stdin");
+//!
+//!     // We drop the handle here which signals EOF to the child process.
+//!     // This tells the child process that it there is no more data on the pipe.
+//!     drop(stdin);
+//!
+//!     let op = child.wait_with_output().await?;
+//!
+//!     // Results should come back in sorted order
+//!     assert_eq!(op.stdout, "bird\ncat\ndog\nfish\nfrog\n".as_bytes());
+//!
+//!     Ok(())
+//! }
+//! ```
+//!
+//! With some coordination, we can also pipe the output of one command into
+//! another.
+//!
+//! ```no_run
+//! use tokio::join;
+//! use tokio::process::Command;
+//! use std::convert::TryInto;
+//! use std::process::Stdio;
+//!
+//! #[tokio::main]
+//! async fn main() -> Result<(), Box<dyn std::error::Error>> {
+//!     let mut echo = Command::new("echo")
+//!         .arg("hello world!")
+//!         .stdout(Stdio::piped())
+//!         .spawn()
+//!         .expect("failed to spawn echo");
+//!
+//!     let tr_stdin: Stdio = echo
+//!         .stdout
+//!         .take()
+//!         .unwrap()
+//!         .try_into()
+//!         .expect("failed to convert to Stdio");
+//!
+//!     let tr = Command::new("tr")
+//!         .arg("a-z")
+//!         .arg("A-Z")
+//!         .stdin(tr_stdin)
+//!         .stdout(Stdio::piped())
+//!         .spawn()
+//!         .expect("failed to spawn tr");
+//!
+//!     let (echo_result, tr_output) = join!(echo.wait(), tr.wait_with_output());
+//!
+//!     assert!(echo_result.unwrap().success());
+//!
+//!     let tr_output = tr_output.expect("failed to await tr");
+//!     assert!(tr_output.status.success());
+//!
+//!     assert_eq!(tr_output.stdout, b"HELLO WORLD!\n");
+//!
+//!     Ok(())
+//! }
+//! ```
+//!
+//! # Caveats
+//!
+//! ## Dropping/Cancellation
+//!
+//! Similar to the behavior to the standard library, and unlike the futures
+//! paradigm of dropping-implies-cancellation, a spawned process will, by
+//! default, continue to execute even after the `Child` handle has been dropped.
+//!
+//! The [`Command::kill_on_drop`] method can be used to modify this behavior
+//! and kill the child process if the `Child` wrapper is dropped before it
+//! has exited.
+//!
+//! ## Unix Processes
+//!
+//! On Unix platforms processes must be "reaped" by their parent process after
+//! they have exited in order to release all OS resources. A child process which
+//! has exited, but has not yet been reaped by its parent is considered a "zombie"
+//! process. Such processes continue to count against limits imposed by the system,
+//! and having too many zombie processes present can prevent additional processes
+//! from being spawned.
+//!
+//! The tokio runtime will, on a best-effort basis, attempt to reap and clean up
+//! any process which it has spawned. No additional guarantees are made with regards
+//! how quickly or how often this procedure will take place.
+//!
+//! It is recommended to avoid dropping a [`Child`] process handle before it has been
+//! fully `await`ed if stricter cleanup guarantees are required.
+//!
+//! [`Command`]: crate::process::Command
+//! [`Command::kill_on_drop`]: crate::process::Command::kill_on_drop
+//! [`Child`]: crate::process::Child
+
+#[path = "unix/mod.rs"]
+#[cfg(unix)]
+mod imp;
+
+#[cfg(unix)]
+pub(crate) mod unix {
+    pub(crate) use super::imp::*;
+}
+
+#[path = "windows.rs"]
+#[cfg(windows)]
+mod imp;
+
+mod kill;
+
+use crate::io::{AsyncRead, AsyncWrite, ReadBuf};
+use crate::process::kill::Kill;
+
+use std::convert::TryInto;
+use std::ffi::OsStr;
+use std::future::Future;
+use std::io;
+#[cfg(unix)]
+use std::os::unix::process::CommandExt;
+#[cfg(windows)]
+use std::os::windows::io::{AsRawHandle, RawHandle};
+#[cfg(windows)]
+use std::os::windows::process::CommandExt;
+use std::path::Path;
+use std::pin::Pin;
+use std::process::{Command as StdCommand, ExitStatus, Output, Stdio};
+use std::task::Context;
+use std::task::Poll;
+
+/// This structure mimics the API of [`std::process::Command`] found in the standard library, but
+/// replaces functions that create a process with an asynchronous variant. The main provided
+/// asynchronous functions are [spawn](Command::spawn), [status](Command::status), and
+/// [output](Command::output).
+///
+/// `Command` uses asynchronous versions of some `std` types (for example [`Child`]).
+///
+/// [`std::process::Command`]: std::process::Command
+/// [`Child`]: struct@Child
+#[derive(Debug)]
+pub struct Command {
+    std: StdCommand,
+    kill_on_drop: bool,
+}
+
+pub(crate) struct SpawnedChild {
+    child: imp::Child,
+    stdin: Option<imp::ChildStdio>,
+    stdout: Option<imp::ChildStdio>,
+    stderr: Option<imp::ChildStdio>,
+}
+
+impl Command {
+    /// Constructs a new `Command` for launching the program at
+    /// path `program`, with the following default configuration:
+    ///
+    /// * No arguments to the program
+    /// * Inherit the current process's environment
+    /// * Inherit the current process's working directory
+    /// * Inherit stdin/stdout/stderr for `spawn` or `status`, but create pipes for `output`
+    ///
+    /// Builder methods are provided to change these defaults and
+    /// otherwise configure the process.
+    ///
+    /// If `program` is not an absolute path, the `PATH` will be searched in
+    /// an OS-defined way.
+    ///
+    /// The search path to be used may be controlled by setting the
+    /// `PATH` environment variable on the Command,
+    /// but this has some implementation limitations on Windows
+    /// (see issue [rust-lang/rust#37519]).
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    /// let command = Command::new("sh");
+    /// ```
+    ///
+    /// [rust-lang/rust#37519]: https://github.com/rust-lang/rust/issues/37519
+    pub fn new<S: AsRef<OsStr>>(program: S) -> Command {
+        Self::from(StdCommand::new(program))
+    }
+
+    /// Cheaply convert to a `&std::process::Command` for places where the type from the standard
+    /// library is expected.
+    pub fn as_std(&self) -> &StdCommand {
+        &self.std
+    }
+
+    /// Adds an argument to pass to the program.
+    ///
+    /// Only one argument can be passed per use. So instead of:
+    ///
+    /// ```no_run
+    /// tokio::process::Command::new("sh")
+    ///   .arg("-C /path/to/repo");
+    /// ```
+    ///
+    /// usage would be:
+    ///
+    /// ```no_run
+    /// tokio::process::Command::new("sh")
+    ///   .arg("-C")
+    ///   .arg("/path/to/repo");
+    /// ```
+    ///
+    /// To pass multiple arguments see [`args`].
+    ///
+    /// [`args`]: method@Self::args
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .arg("-l")
+    ///         .arg("-a");
+    /// ```
+    pub fn arg<S: AsRef<OsStr>>(&mut self, arg: S) -> &mut Command {
+        self.std.arg(arg);
+        self
+    }
+
+    /// Adds multiple arguments to pass to the program.
+    ///
+    /// To pass a single argument see [`arg`].
+    ///
+    /// [`arg`]: method@Self::arg
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .args(&["-l", "-a"]);
+    /// ```
+    pub fn args<I, S>(&mut self, args: I) -> &mut Command
+    where
+        I: IntoIterator<Item = S>,
+        S: AsRef<OsStr>,
+    {
+        self.std.args(args);
+        self
+    }
+
+    /// Inserts or updates an environment variable mapping.
+    ///
+    /// Note that environment variable names are case-insensitive (but case-preserving) on Windows,
+    /// and case-sensitive on all other platforms.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .env("PATH", "/bin");
+    /// ```
+    pub fn env<K, V>(&mut self, key: K, val: V) -> &mut Command
+    where
+        K: AsRef<OsStr>,
+        V: AsRef<OsStr>,
+    {
+        self.std.env(key, val);
+        self
+    }
+
+    /// Adds or updates multiple environment variable mappings.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    /// use std::process::{Stdio};
+    /// use std::env;
+    /// use std::collections::HashMap;
+    ///
+    /// let filtered_env : HashMap<String, String> =
+    ///     env::vars().filter(|&(ref k, _)|
+    ///         k == "TERM" || k == "TZ" || k == "LANG" || k == "PATH"
+    ///     ).collect();
+    ///
+    /// let command = Command::new("printenv")
+    ///         .stdin(Stdio::null())
+    ///         .stdout(Stdio::inherit())
+    ///         .env_clear()
+    ///         .envs(&filtered_env);
+    /// ```
+    pub fn envs<I, K, V>(&mut self, vars: I) -> &mut Command
+    where
+        I: IntoIterator<Item = (K, V)>,
+        K: AsRef<OsStr>,
+        V: AsRef<OsStr>,
+    {
+        self.std.envs(vars);
+        self
+    }
+
+    /// Removes an environment variable mapping.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .env_remove("PATH");
+    /// ```
+    pub fn env_remove<K: AsRef<OsStr>>(&mut self, key: K) -> &mut Command {
+        self.std.env_remove(key);
+        self
+    }
+
+    /// Clears the entire environment map for the child process.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .env_clear();
+    /// ```
+    pub fn env_clear(&mut self) -> &mut Command {
+        self.std.env_clear();
+        self
+    }
+
+    /// Sets the working directory for the child process.
+    ///
+    /// # Platform-specific behavior
+    ///
+    /// If the program path is relative (e.g., `"./script.sh"`), it's ambiguous
+    /// whether it should be interpreted relative to the parent's working
+    /// directory or relative to `current_dir`. The behavior in this case is
+    /// platform specific and unstable, and it's recommended to use
+    /// [`canonicalize`] to get an absolute program path instead.
+    ///
+    /// [`canonicalize`]: crate::fs::canonicalize()
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .current_dir("/bin");
+    /// ```
+    pub fn current_dir<P: AsRef<Path>>(&mut self, dir: P) -> &mut Command {
+        self.std.current_dir(dir);
+        self
+    }
+
+    /// Sets configuration for the child process's standard input (stdin) handle.
+    ///
+    /// Defaults to [`inherit`] when used with `spawn` or `status`, and
+    /// defaults to [`piped`] when used with `output`.
+    ///
+    /// [`inherit`]: std::process::Stdio::inherit
+    /// [`piped`]: std::process::Stdio::piped
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use std::process::{Stdio};
+    /// use tokio::process::Command;
+    ///
+    /// let command = Command::new("ls")
+    ///         .stdin(Stdio::null());
+    /// ```
+    pub fn stdin<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
+        self.std.stdin(cfg);
+        self
+    }
+
+    /// Sets configuration for the child process's standard output (stdout) handle.
+    ///
+    /// Defaults to [`inherit`] when used with `spawn` or `status`, and
+    /// defaults to [`piped`] when used with `output`.
+    ///
+    /// [`inherit`]: std::process::Stdio::inherit
+    /// [`piped`]: std::process::Stdio::piped
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    /// use std::process::Stdio;
+    ///
+    /// let command = Command::new("ls")
+    ///         .stdout(Stdio::null());
+    /// ```
+    pub fn stdout<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
+        self.std.stdout(cfg);
+        self
+    }
+
+    /// Sets configuration for the child process's standard error (stderr) handle.
+    ///
+    /// Defaults to [`inherit`] when used with `spawn` or `status`, and
+    /// defaults to [`piped`] when used with `output`.
+    ///
+    /// [`inherit`]: std::process::Stdio::inherit
+    /// [`piped`]: std::process::Stdio::piped
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    /// use std::process::{Stdio};
+    ///
+    /// let command = Command::new("ls")
+    ///         .stderr(Stdio::null());
+    /// ```
+    pub fn stderr<T: Into<Stdio>>(&mut self, cfg: T) -> &mut Command {
+        self.std.stderr(cfg);
+        self
+    }
+
+    /// Controls whether a `kill` operation should be invoked on a spawned child
+    /// process when its corresponding `Child` handle is dropped.
+    ///
+    /// By default, this value is assumed to be `false`, meaning the next spawned
+    /// process will not be killed on drop, similar to the behavior of the standard
+    /// library.
+    ///
+    /// # Caveats
+    ///
+    /// On Unix platforms processes must be "reaped" by their parent process after
+    /// they have exited in order to release all OS resources. A child process which
+    /// has exited, but has not yet been reaped by its parent is considered a "zombie"
+    /// process. Such processes continue to count against limits imposed by the system,
+    /// and having too many zombie processes present can prevent additional processes
+    /// from being spawned.
+    ///
+    /// Although issuing a `kill` signal to the child process is a synchronous
+    /// operation, the resulting zombie process cannot be `.await`ed inside of the
+    /// destructor to avoid blocking other tasks. The tokio runtime will, on a
+    /// best-effort basis, attempt to reap and clean up such processes in the
+    /// background, but makes no additional guarantees are made with regards
+    /// how quickly or how often this procedure will take place.
+    ///
+    /// If stronger guarantees are required, it is recommended to avoid dropping
+    /// a [`Child`] handle where possible, and instead utilize `child.wait().await`
+    /// or `child.kill().await` where possible.
+    pub fn kill_on_drop(&mut self, kill_on_drop: bool) -> &mut Command {
+        self.kill_on_drop = kill_on_drop;
+        self
+    }
+
+    /// Sets the [process creation flags][1] to be passed to `CreateProcess`.
+    ///
+    /// These will always be ORed with `CREATE_UNICODE_ENVIRONMENT`.
+    ///
+    /// [1]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms684863(v=vs.85).aspx
+    #[cfg(windows)]
+    #[cfg_attr(docsrs, doc(cfg(windows)))]
+    pub fn creation_flags(&mut self, flags: u32) -> &mut Command {
+        self.std.creation_flags(flags);
+        self
+    }
+
+    /// Sets the child process's user ID. This translates to a
+    /// `setuid` call in the child process. Failure in the `setuid`
+    /// call will cause the spawn to fail.
+    #[cfg(unix)]
+    #[cfg_attr(docsrs, doc(cfg(unix)))]
+    pub fn uid(&mut self, id: u32) -> &mut Command {
+        self.std.uid(id);
+        self
+    }
+
+    /// Similar to `uid` but sets the group ID of the child process. This has
+    /// the same semantics as the `uid` field.
+    #[cfg(unix)]
+    #[cfg_attr(docsrs, doc(cfg(unix)))]
+    pub fn gid(&mut self, id: u32) -> &mut Command {
+        self.std.gid(id);
+        self
+    }
+
+    /// Sets executable argument.
+    ///
+    /// Set the first process argument, `argv[0]`, to something other than the
+    /// default executable path.
+    #[cfg(unix)]
+    #[cfg_attr(docsrs, doc(cfg(unix)))]
+    pub fn arg0<S>(&mut self, arg: S) -> &mut Command
+    where
+        S: AsRef<OsStr>,
+    {
+        self.std.arg0(arg);
+        self
+    }
+
+    /// Schedules a closure to be run just before the `exec` function is
+    /// invoked.
+    ///
+    /// The closure is allowed to return an I/O error whose OS error code will
+    /// be communicated back to the parent and returned as an error from when
+    /// the spawn was requested.
+    ///
+    /// Multiple closures can be registered and they will be called in order of
+    /// their registration. If a closure returns `Err` then no further closures
+    /// will be called and the spawn operation will immediately return with a
+    /// failure.
+    ///
+    /// # Safety
+    ///
+    /// This closure will be run in the context of the child process after a
+    /// `fork`. This primarily means that any modifications made to memory on
+    /// behalf of this closure will **not** be visible to the parent process.
+    /// This is often a very constrained environment where normal operations
+    /// like `malloc` or acquiring a mutex are not guaranteed to work (due to
+    /// other threads perhaps still running when the `fork` was run).
+    ///
+    /// This also means that all resources such as file descriptors and
+    /// memory-mapped regions got duplicated. It is your responsibility to make
+    /// sure that the closure does not violate library invariants by making
+    /// invalid use of these duplicates.
+    ///
+    /// When this closure is run, aspects such as the stdio file descriptors and
+    /// working directory have successfully been changed, so output to these
+    /// locations may not appear where intended.
+    #[cfg(unix)]
+    #[cfg_attr(docsrs, doc(cfg(unix)))]
+    pub unsafe fn pre_exec<F>(&mut self, f: F) -> &mut Command
+    where
+        F: FnMut() -> io::Result<()> + Send + Sync + 'static,
+    {
+        self.std.pre_exec(f);
+        self
+    }
+
+    /// Executes the command as a child process, returning a handle to it.
+    ///
+    /// By default, stdin, stdout and stderr are inherited from the parent.
+    ///
+    /// This method will spawn the child process synchronously and return a
+    /// handle to a future-aware child process. The `Child` returned implements
+    /// `Future` itself to acquire the `ExitStatus` of the child, and otherwise
+    /// the `Child` has methods to acquire handles to the stdin, stdout, and
+    /// stderr streams.
+    ///
+    /// All I/O this child does will be associated with the current default
+    /// event loop.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// async fn run_ls() -> std::process::ExitStatus {
+    ///     Command::new("ls")
+    ///         .spawn()
+    ///         .expect("ls command failed to start")
+    ///         .wait()
+    ///         .await
+    ///         .expect("ls command failed to run")
+    /// }
+    /// ```
+    ///
+    /// # Caveats
+    ///
+    /// ## Dropping/Cancellation
+    ///
+    /// Similar to the behavior to the standard library, and unlike the futures
+    /// paradigm of dropping-implies-cancellation, a spawned process will, by
+    /// default, continue to execute even after the `Child` handle has been dropped.
+    ///
+    /// The [`Command::kill_on_drop`] method can be used to modify this behavior
+    /// and kill the child process if the `Child` wrapper is dropped before it
+    /// has exited.
+    ///
+    /// ## Unix Processes
+    ///
+    /// On Unix platforms processes must be "reaped" by their parent process after
+    /// they have exited in order to release all OS resources. A child process which
+    /// has exited, but has not yet been reaped by its parent is considered a "zombie"
+    /// process. Such processes continue to count against limits imposed by the system,
+    /// and having too many zombie processes present can prevent additional processes
+    /// from being spawned.
+    ///
+    /// The tokio runtime will, on a best-effort basis, attempt to reap and clean up
+    /// any process which it has spawned. No additional guarantees are made with regards
+    /// how quickly or how often this procedure will take place.
+    ///
+    /// It is recommended to avoid dropping a [`Child`] process handle before it has been
+    /// fully `await`ed if stricter cleanup guarantees are required.
+    ///
+    /// [`Command`]: crate::process::Command
+    /// [`Command::kill_on_drop`]: crate::process::Command::kill_on_drop
+    /// [`Child`]: crate::process::Child
+    ///
+    /// # Errors
+    ///
+    /// On Unix platforms this method will fail with `std::io::ErrorKind::WouldBlock`
+    /// if the system process limit is reached (which includes other applications
+    /// running on the system).
+    pub fn spawn(&mut self) -> io::Result<Child> {
+        imp::spawn_child(&mut self.std).map(|spawned_child| Child {
+            child: FusedChild::Child(ChildDropGuard {
+                inner: spawned_child.child,
+                kill_on_drop: self.kill_on_drop,
+            }),
+            stdin: spawned_child.stdin.map(|inner| ChildStdin { inner }),
+            stdout: spawned_child.stdout.map(|inner| ChildStdout { inner }),
+            stderr: spawned_child.stderr.map(|inner| ChildStderr { inner }),
+        })
+    }
+
+    /// Executes the command as a child process, waiting for it to finish and
+    /// collecting its exit status.
+    ///
+    /// By default, stdin, stdout and stderr are inherited from the parent.
+    /// If any input/output handles are set to a pipe then they will be immediately
+    /// closed after the child is spawned.
+    ///
+    /// All I/O this child does will be associated with the current default
+    /// event loop.
+    ///
+    /// The destructor of the future returned by this function will kill
+    /// the child if [`kill_on_drop`] is set to true.
+    ///
+    /// [`kill_on_drop`]: fn@Self::kill_on_drop
+    ///
+    /// # Errors
+    ///
+    /// This future will return an error if the child process cannot be spawned
+    /// or if there is an error while awaiting its status.
+    ///
+    /// On Unix platforms this method will fail with `std::io::ErrorKind::WouldBlock`
+    /// if the system process limit is reached (which includes other applications
+    /// running on the system).
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// async fn run_ls() -> std::process::ExitStatus {
+    ///     Command::new("ls")
+    ///         .status()
+    ///         .await
+    ///         .expect("ls command failed to run")
+    /// }
+    /// ```
+    pub fn status(&mut self) -> impl Future<Output = io::Result<ExitStatus>> {
+        let child = self.spawn();
+
+        async {
+            let mut child = child?;
+
+            // Ensure we close any stdio handles so we can't deadlock
+            // waiting on the child which may be waiting to read/write
+            // to a pipe we're holding.
+            child.stdin.take();
+            child.stdout.take();
+            child.stderr.take();
+
+            child.wait().await
+        }
+    }
+
+    /// Executes the command as a child process, waiting for it to finish and
+    /// collecting all of its output.
+    ///
+    /// > **Note**: this method, unlike the standard library, will
+    /// > unconditionally configure the stdout/stderr handles to be pipes, even
+    /// > if they have been previously configured. If this is not desired then
+    /// > the `spawn` method should be used in combination with the
+    /// > `wait_with_output` method on child.
+    ///
+    /// This method will return a future representing the collection of the
+    /// child process's stdout/stderr. It will resolve to
+    /// the `Output` type in the standard library, containing `stdout` and
+    /// `stderr` as `Vec<u8>` along with an `ExitStatus` representing how the
+    /// process exited.
+    ///
+    /// All I/O this child does will be associated with the current default
+    /// event loop.
+    ///
+    /// The destructor of the future returned by this function will kill
+    /// the child if [`kill_on_drop`] is set to true.
+    ///
+    /// [`kill_on_drop`]: fn@Self::kill_on_drop
+    ///
+    /// # Errors
+    ///
+    /// This future will return an error if the child process cannot be spawned
+    /// or if there is an error while awaiting its status.
+    ///
+    /// On Unix platforms this method will fail with `std::io::ErrorKind::WouldBlock`
+    /// if the system process limit is reached (which includes other applications
+    /// running on the system).
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    ///
+    /// async fn run_ls() {
+    ///     let output: std::process::Output = Command::new("ls")
+    ///         .output()
+    ///         .await
+    ///         .expect("ls command failed to run");
+    ///     println!("stderr of ls: {:?}", output.stderr);
+    /// }
+    /// ```
+    pub fn output(&mut self) -> impl Future<Output = io::Result<Output>> {
+        self.std.stdout(Stdio::piped());
+        self.std.stderr(Stdio::piped());
+
+        let child = self.spawn();
+
+        async { child?.wait_with_output().await }
+    }
+}
+
+impl From<StdCommand> for Command {
+    fn from(std: StdCommand) -> Command {
+        Command {
+            std,
+            kill_on_drop: false,
+        }
+    }
+}
+
+/// A drop guard which can ensure the child process is killed on drop if specified.
+#[derive(Debug)]
+struct ChildDropGuard<T: Kill> {
+    inner: T,
+    kill_on_drop: bool,
+}
+
+impl<T: Kill> Kill for ChildDropGuard<T> {
+    fn kill(&mut self) -> io::Result<()> {
+        let ret = self.inner.kill();
+
+        if ret.is_ok() {
+            self.kill_on_drop = false;
+        }
+
+        ret
+    }
+}
+
+impl<T: Kill> Drop for ChildDropGuard<T> {
+    fn drop(&mut self) {
+        if self.kill_on_drop {
+            drop(self.kill());
+        }
+    }
+}
+
+impl<T, E, F> Future for ChildDropGuard<F>
+where
+    F: Future<Output = Result<T, E>> + Kill + Unpin,
+{
+    type Output = Result<T, E>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        // Keep track of task budget
+        let coop = ready!(crate::coop::poll_proceed(cx));
+
+        let ret = Pin::new(&mut self.inner).poll(cx);
+
+        if let Poll::Ready(Ok(_)) = ret {
+            // Avoid the overhead of trying to kill a reaped process
+            self.kill_on_drop = false;
+        }
+
+        if ret.is_ready() {
+            coop.made_progress();
+        }
+
+        ret
+    }
+}
+
+/// Keeps track of the exit status of a child process without worrying about
+/// polling the underlying futures even after they have completed.
+#[derive(Debug)]
+enum FusedChild {
+    Child(ChildDropGuard<imp::Child>),
+    Done(ExitStatus),
+}
+
+/// Representation of a child process spawned onto an event loop.
+///
+/// # Caveats
+/// Similar to the behavior to the standard library, and unlike the futures
+/// paradigm of dropping-implies-cancellation, a spawned process will, by
+/// default, continue to execute even after the `Child` handle has been dropped.
+///
+/// The `Command::kill_on_drop` method can be used to modify this behavior
+/// and kill the child process if the `Child` wrapper is dropped before it
+/// has exited.
+#[derive(Debug)]
+pub struct Child {
+    child: FusedChild,
+
+    /// The handle for writing to the child's standard input (stdin), if it has
+    /// been captured. To avoid partially moving the `child` and thus blocking
+    /// yourself from calling functions on `child` while using `stdin`, you might
+    /// find it helpful to do:
+    ///
+    /// ```no_run
+    /// # let mut child = tokio::process::Command::new("echo").spawn().unwrap();
+    /// let stdin = child.stdin.take().unwrap();
+    /// ```
+    pub stdin: Option<ChildStdin>,
+
+    /// The handle for reading from the child's standard output (stdout), if it
+    /// has been captured. You might find it helpful to do
+    ///
+    /// ```no_run
+    /// # let mut child = tokio::process::Command::new("echo").spawn().unwrap();
+    /// let stdout = child.stdout.take().unwrap();
+    /// ```
+    ///
+    /// to avoid partially moving the `child` and thus blocking yourself from calling
+    /// functions on `child` while using `stdout`.
+    pub stdout: Option<ChildStdout>,
+
+    /// The handle for reading from the child's standard error (stderr), if it
+    /// has been captured. You might find it helpful to do
+    ///
+    /// ```no_run
+    /// # let mut child = tokio::process::Command::new("echo").spawn().unwrap();
+    /// let stderr = child.stderr.take().unwrap();
+    /// ```
+    ///
+    /// to avoid partially moving the `child` and thus blocking yourself from calling
+    /// functions on `child` while using `stderr`.
+    pub stderr: Option<ChildStderr>,
+}
+
+impl Child {
+    /// Returns the OS-assigned process identifier associated with this child
+    /// while it is still running.
+    ///
+    /// Once the child has been polled to completion this will return `None`.
+    /// This is done to avoid confusion on platforms like Unix where the OS
+    /// identifier could be reused once the process has completed.
+    pub fn id(&self) -> Option<u32> {
+        match &self.child {
+            FusedChild::Child(child) => Some(child.inner.id()),
+            FusedChild::Done(_) => None,
+        }
+    }
+
+    /// Extracts the raw handle of the process associated with this child while
+    /// it is still running. Returns `None` if the child has exited.
+    #[cfg(windows)]
+    pub fn raw_handle(&self) -> Option<RawHandle> {
+        match &self.child {
+            FusedChild::Child(c) => Some(c.inner.as_raw_handle()),
+            FusedChild::Done(_) => None,
+        }
+    }
+
+    /// Attempts to force the child to exit, but does not wait for the request
+    /// to take effect.
+    ///
+    /// On Unix platforms, this is the equivalent to sending a SIGKILL. Note
+    /// that on Unix platforms it is possible for a zombie process to remain
+    /// after a kill is sent; to avoid this, the caller should ensure that either
+    /// `child.wait().await` or `child.try_wait()` is invoked successfully.
+    pub fn start_kill(&mut self) -> io::Result<()> {
+        match &mut self.child {
+            FusedChild::Child(child) => child.kill(),
+            FusedChild::Done(_) => Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                "invalid argument: can't kill an exited process",
+            )),
+        }
+    }
+
+    /// Forces the child to exit.
+    ///
+    /// This is equivalent to sending a SIGKILL on unix platforms.
+    ///
+    /// If the child has to be killed remotely, it is possible to do it using
+    /// a combination of the select! macro and a oneshot channel. In the following
+    /// example, the child will run until completion unless a message is sent on
+    /// the oneshot channel. If that happens, the child is killed immediately
+    /// using the `.kill()` method.
+    ///
+    /// ```no_run
+    /// use tokio::process::Command;
+    /// use tokio::sync::oneshot::channel;
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let (send, recv) = channel::<()>();
+    ///     let mut child = Command::new("sleep").arg("1").spawn().unwrap();
+    ///     tokio::spawn(async move { send.send(()) });
+    ///     tokio::select! {
+    ///         _ = child.wait() => {}
+    ///         _ = recv => child.kill().await.expect("kill failed"),
+    ///     }
+    /// }
+    /// ```
+    pub async fn kill(&mut self) -> io::Result<()> {
+        self.start_kill()?;
+        self.wait().await?;
+        Ok(())
+    }
+
+    /// Waits for the child to exit completely, returning the status that it
+    /// exited with. This function will continue to have the same return value
+    /// after it has been called at least once.
+    ///
+    /// The stdin handle to the child process, if any, will be closed
+    /// before waiting. This helps avoid deadlock: it ensures that the
+    /// child does not block waiting for input from the parent, while
+    /// the parent waits for the child to exit.
+    ///
+    /// If the caller wishes to explicitly control when the child's stdin
+    /// handle is closed, they may `.take()` it before calling `.wait()`:
+    ///
+    /// ```
+    /// # #[cfg(not(unix))]fn main(){}
+    /// # #[cfg(unix)]
+    /// use tokio::io::AsyncWriteExt;
+    /// # #[cfg(unix)]
+    /// use tokio::process::Command;
+    /// # #[cfg(unix)]
+    /// use std::process::Stdio;
+    ///
+    /// # #[cfg(unix)]
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let mut child = Command::new("cat")
+    ///         .stdin(Stdio::piped())
+    ///         .spawn()
+    ///         .unwrap();
+    ///
+    ///     let mut stdin = child.stdin.take().unwrap();
+    ///     tokio::spawn(async move {
+    ///         // do something with stdin here...
+    ///         stdin.write_all(b"hello world\n").await.unwrap();
+    ///
+    ///         // then drop when finished
+    ///         drop(stdin);
+    ///     });
+    ///
+    ///     // wait for the process to complete
+    ///     let _ = child.wait().await;
+    /// }
+    /// ```
+    pub async fn wait(&mut self) -> io::Result<ExitStatus> {
+        // Ensure stdin is closed so the child isn't stuck waiting on
+        // input while the parent is waiting for it to exit.
+        drop(self.stdin.take());
+
+        match &mut self.child {
+            FusedChild::Done(exit) => Ok(*exit),
+            FusedChild::Child(child) => {
+                let ret = child.await;
+
+                if let Ok(exit) = ret {
+                    self.child = FusedChild::Done(exit);
+                }
+
+                ret
+            }
+        }
+    }
+
+    /// Attempts to collect the exit status of the child if it has already
+    /// exited.
+    ///
+    /// This function will not block the calling thread and will only
+    /// check to see if the child process has exited or not. If the child has
+    /// exited then on Unix the process ID is reaped. This function is
+    /// guaranteed to repeatedly return a successful exit status so long as the
+    /// child has already exited.
+    ///
+    /// If the child has exited, then `Ok(Some(status))` is returned. If the
+    /// exit status is not available at this time then `Ok(None)` is returned.
+    /// If an error occurs, then that error is returned.
+    ///
+    /// Note that unlike `wait`, this function will not attempt to drop stdin,
+    /// nor will it wake the current task if the child exits.
+    pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+        match &mut self.child {
+            FusedChild::Done(exit) => Ok(Some(*exit)),
+            FusedChild::Child(guard) => {
+                let ret = guard.inner.try_wait();
+
+                if let Ok(Some(exit)) = ret {
+                    // Avoid the overhead of trying to kill a reaped process
+                    guard.kill_on_drop = false;
+                    self.child = FusedChild::Done(exit);
+                }
+
+                ret
+            }
+        }
+    }
+
+    /// Returns a future that will resolve to an `Output`, containing the exit
+    /// status, stdout, and stderr of the child process.
+    ///
+    /// The returned future will simultaneously waits for the child to exit and
+    /// collect all remaining output on the stdout/stderr handles, returning an
+    /// `Output` instance.
+    ///
+    /// The stdin handle to the child process, if any, will be closed before
+    /// waiting. This helps avoid deadlock: it ensures that the child does not
+    /// block waiting for input from the parent, while the parent waits for the
+    /// child to exit.
+    ///
+    /// By default, stdin, stdout and stderr are inherited from the parent. In
+    /// order to capture the output into this `Output` it is necessary to create
+    /// new pipes between parent and child. Use `stdout(Stdio::piped())` or
+    /// `stderr(Stdio::piped())`, respectively, when creating a `Command`.
+    pub async fn wait_with_output(mut self) -> io::Result<Output> {
+        use crate::future::try_join3;
+
+        async fn read_to_end<A: AsyncRead + Unpin>(io: &mut Option<A>) -> io::Result<Vec<u8>> {
+            let mut vec = Vec::new();
+            if let Some(io) = io.as_mut() {
+                crate::io::util::read_to_end(io, &mut vec).await?;
+            }
+            Ok(vec)
+        }
+
+        let mut stdout_pipe = self.stdout.take();
+        let mut stderr_pipe = self.stderr.take();
+
+        let stdout_fut = read_to_end(&mut stdout_pipe);
+        let stderr_fut = read_to_end(&mut stderr_pipe);
+
+        let (status, stdout, stderr) = try_join3(self.wait(), stdout_fut, stderr_fut).await?;
+
+        // Drop happens after `try_join` due to <https://github.com/tokio-rs/tokio/issues/4309>
+        drop(stdout_pipe);
+        drop(stderr_pipe);
+
+        Ok(Output {
+            status,
+            stdout,
+            stderr,
+        })
+    }
+}
+
+/// The standard input stream for spawned children.
+///
+/// This type implements the `AsyncWrite` trait to pass data to the stdin handle of
+/// handle of a child process asynchronously.
+#[derive(Debug)]
+pub struct ChildStdin {
+    inner: imp::ChildStdio,
+}
+
+/// The standard output stream for spawned children.
+///
+/// This type implements the `AsyncRead` trait to read data from the stdout
+/// handle of a child process asynchronously.
+#[derive(Debug)]
+pub struct ChildStdout {
+    inner: imp::ChildStdio,
+}
+
+/// The standard error stream for spawned children.
+///
+/// This type implements the `AsyncRead` trait to read data from the stderr
+/// handle of a child process asynchronously.
+#[derive(Debug)]
+pub struct ChildStderr {
+    inner: imp::ChildStdio,
+}
+
+impl ChildStdin {
+    /// Creates an asynchronous `ChildStdin` from a synchronous one.
+    ///
+    /// # Errors
+    ///
+    /// This method may fail if an error is encountered when setting the pipe to
+    /// non-blocking mode, or when registering the pipe with the runtime's IO
+    /// driver.
+    pub fn from_std(inner: std::process::ChildStdin) -> io::Result<Self> {
+        Ok(Self {
+            inner: imp::stdio(inner)?,
+        })
+    }
+}
+
+impl ChildStdout {
+    /// Creates an asynchronous `ChildStderr` from a synchronous one.
+    ///
+    /// # Errors
+    ///
+    /// This method may fail if an error is encountered when setting the pipe to
+    /// non-blocking mode, or when registering the pipe with the runtime's IO
+    /// driver.
+    pub fn from_std(inner: std::process::ChildStdout) -> io::Result<Self> {
+        Ok(Self {
+            inner: imp::stdio(inner)?,
+        })
+    }
+}
+
+impl ChildStderr {
+    /// Creates an asynchronous `ChildStderr` from a synchronous one.
+    ///
+    /// # Errors
+    ///
+    /// This method may fail if an error is encountered when setting the pipe to
+    /// non-blocking mode, or when registering the pipe with the runtime's IO
+    /// driver.
+    pub fn from_std(inner: std::process::ChildStderr) -> io::Result<Self> {
+        Ok(Self {
+            inner: imp::stdio(inner)?,
+        })
+    }
+}
+
+impl AsyncWrite for ChildStdin {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<io::Result<usize>> {
+        self.inner.poll_write(cx, buf)
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+}
+
+impl AsyncRead for ChildStdout {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        // Safety: pipes support reading into uninitialized memory
+        unsafe { self.inner.poll_read(cx, buf) }
+    }
+}
+
+impl AsyncRead for ChildStderr {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
+        // Safety: pipes support reading into uninitialized memory
+        unsafe { self.inner.poll_read(cx, buf) }
+    }
+}
+
+impl TryInto<Stdio> for ChildStdin {
+    type Error = io::Error;
+
+    fn try_into(self) -> Result<Stdio, Self::Error> {
+        imp::convert_to_stdio(self.inner)
+    }
+}
+
+impl TryInto<Stdio> for ChildStdout {
+    type Error = io::Error;
+
+    fn try_into(self) -> Result<Stdio, Self::Error> {
+        imp::convert_to_stdio(self.inner)
+    }
+}
+
+impl TryInto<Stdio> for ChildStderr {
+    type Error = io::Error;
+
+    fn try_into(self) -> Result<Stdio, Self::Error> {
+        imp::convert_to_stdio(self.inner)
+    }
+}
+
+#[cfg(unix)]
+mod sys {
+    use std::os::unix::io::{AsRawFd, RawFd};
+
+    use super::{ChildStderr, ChildStdin, ChildStdout};
+
+    impl AsRawFd for ChildStdin {
+        fn as_raw_fd(&self) -> RawFd {
+            self.inner.as_raw_fd()
+        }
+    }
+
+    impl AsRawFd for ChildStdout {
+        fn as_raw_fd(&self) -> RawFd {
+            self.inner.as_raw_fd()
+        }
+    }
+
+    impl AsRawFd for ChildStderr {
+        fn as_raw_fd(&self) -> RawFd {
+            self.inner.as_raw_fd()
+        }
+    }
+}
+
+#[cfg(windows)]
+mod sys {
+    use std::os::windows::io::{AsRawHandle, RawHandle};
+
+    use super::{ChildStderr, ChildStdin, ChildStdout};
+
+    impl AsRawHandle for ChildStdin {
+        fn as_raw_handle(&self) -> RawHandle {
+            self.inner.as_raw_handle()
+        }
+    }
+
+    impl AsRawHandle for ChildStdout {
+        fn as_raw_handle(&self) -> RawHandle {
+            self.inner.as_raw_handle()
+        }
+    }
+
+    impl AsRawHandle for ChildStderr {
+        fn as_raw_handle(&self) -> RawHandle {
+            self.inner.as_raw_handle()
+        }
+    }
+}
+
+#[cfg(all(test, not(loom)))]
+mod test {
+    use super::kill::Kill;
+    use super::ChildDropGuard;
+
+    use futures::future::FutureExt;
+    use std::future::Future;
+    use std::io;
+    use std::pin::Pin;
+    use std::task::{Context, Poll};
+
+    struct Mock {
+        num_kills: usize,
+        num_polls: usize,
+        poll_result: Poll<Result<(), ()>>,
+    }
+
+    impl Mock {
+        fn new() -> Self {
+            Self::with_result(Poll::Pending)
+        }
+
+        fn with_result(result: Poll<Result<(), ()>>) -> Self {
+            Self {
+                num_kills: 0,
+                num_polls: 0,
+                poll_result: result,
+            }
+        }
+    }
+
+    impl Kill for Mock {
+        fn kill(&mut self) -> io::Result<()> {
+            self.num_kills += 1;
+            Ok(())
+        }
+    }
+
+    impl Future for Mock {
+        type Output = Result<(), ()>;
+
+        fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+            let inner = Pin::get_mut(self);
+            inner.num_polls += 1;
+            inner.poll_result
+        }
+    }
+
+    #[test]
+    fn kills_on_drop_if_specified() {
+        let mut mock = Mock::new();
+
+        {
+            let guard = ChildDropGuard {
+                inner: &mut mock,
+                kill_on_drop: true,
+            };
+            drop(guard);
+        }
+
+        assert_eq!(1, mock.num_kills);
+        assert_eq!(0, mock.num_polls);
+    }
+
+    #[test]
+    fn no_kill_on_drop_by_default() {
+        let mut mock = Mock::new();
+
+        {
+            let guard = ChildDropGuard {
+                inner: &mut mock,
+                kill_on_drop: false,
+            };
+            drop(guard);
+        }
+
+        assert_eq!(0, mock.num_kills);
+        assert_eq!(0, mock.num_polls);
+    }
+
+    #[test]
+    fn no_kill_if_already_killed() {
+        let mut mock = Mock::new();
+
+        {
+            let mut guard = ChildDropGuard {
+                inner: &mut mock,
+                kill_on_drop: true,
+            };
+            let _ = guard.kill();
+            drop(guard);
+        }
+
+        assert_eq!(1, mock.num_kills);
+        assert_eq!(0, mock.num_polls);
+    }
+
+    #[test]
+    fn no_kill_if_reaped() {
+        let mut mock_pending = Mock::with_result(Poll::Pending);
+        let mut mock_reaped = Mock::with_result(Poll::Ready(Ok(())));
+        let mut mock_err = Mock::with_result(Poll::Ready(Err(())));
+
+        let waker = futures::task::noop_waker();
+        let mut context = Context::from_waker(&waker);
+        {
+            let mut guard = ChildDropGuard {
+                inner: &mut mock_pending,
+                kill_on_drop: true,
+            };
+            let _ = guard.poll_unpin(&mut context);
+
+            let mut guard = ChildDropGuard {
+                inner: &mut mock_reaped,
+                kill_on_drop: true,
+            };
+            let _ = guard.poll_unpin(&mut context);
+
+            let mut guard = ChildDropGuard {
+                inner: &mut mock_err,
+                kill_on_drop: true,
+            };
+            let _ = guard.poll_unpin(&mut context);
+        }
+
+        assert_eq!(1, mock_pending.num_kills);
+        assert_eq!(1, mock_pending.num_polls);
+
+        assert_eq!(0, mock_reaped.num_kills);
+        assert_eq!(1, mock_reaped.num_polls);
+
+        assert_eq!(1, mock_err.num_kills);
+        assert_eq!(1, mock_err.num_polls);
+    }
+}
diff --git a/third_party/rust/tokio/src/process/unix/driver.rs b/third_party/rust/tokio/src/process/unix/driver.rs
new file mode 100644
index 0000000000..84dc8fbd02
--- /dev/null
+++ b/third_party/rust/tokio/src/process/unix/driver.rs
@@ -0,0 +1,58 @@
+#![cfg_attr(not(feature = "rt"), allow(dead_code))]
+
+//! Process driver.
+
+use crate::park::Park;
+use crate::process::unix::GlobalOrphanQueue;
+use crate::signal::unix::driver::{Driver as SignalDriver, Handle as SignalHandle};
+
+use std::io;
+use std::time::Duration;
+
+/// Responsible for cleaning up orphaned child processes on Unix platforms.
+#[derive(Debug)]
+pub(crate) struct Driver {
+    park: SignalDriver,
+    signal_handle: SignalHandle,
+}
+
+// ===== impl Driver =====
+
+impl Driver {
+    /// Creates a new signal `Driver` instance that delegates wakeups to `park`.
+    pub(crate) fn new(park: SignalDriver) -> Self {
+        let signal_handle = park.handle();
+
+        Self {
+            park,
+            signal_handle,
+        }
+    }
+}
+
+// ===== impl Park for Driver =====
+
+impl Park for Driver {
+    type Unpark = <SignalDriver as Park>::Unpark;
+    type Error = io::Error;
+
+    fn unpark(&self) -> Self::Unpark {
+        self.park.unpark()
+    }
+
+    fn park(&mut self) -> Result<(), Self::Error> {
+        self.park.park()?;
+        GlobalOrphanQueue::reap_orphans(&self.signal_handle);
+        Ok(())
+    }
+
+    fn park_timeout(&mut self, duration: Duration) -> Result<(), Self::Error> {
+        self.park.park_timeout(duration)?;
+        GlobalOrphanQueue::reap_orphans(&self.signal_handle);
+        Ok(())
+    }
+
+    fn shutdown(&mut self) {
+        self.park.shutdown()
+    }
+}
diff --git a/third_party/rust/tokio/src/process/unix/mod.rs b/third_party/rust/tokio/src/process/unix/mod.rs
new file mode 100644
index 0000000000..576fe6cb47
--- /dev/null
+++ b/third_party/rust/tokio/src/process/unix/mod.rs
@@ -0,0 +1,250 @@
+//! Unix handling of child processes.
+//!
+//! Right now the only "fancy" thing about this is how we implement the
+//! `Future` implementation on `Child` to get the exit status. Unix offers
+//! no way to register a child with epoll, and the only real way to get a
+//! notification when a process exits is the SIGCHLD signal.
+//!
+//! Signal handling in general is *super* hairy and complicated, and it's even
+//! more complicated here with the fact that signals are coalesced, so we may
+//! not get a SIGCHLD-per-child.
+//!
+//! Our best approximation here is to check *all spawned processes* for all
+//! SIGCHLD signals received. To do that we create a `Signal`, implemented in
+//! the `tokio-net` crate, which is a stream over signals being received.
+//!
+//! Later when we poll the process's exit status we simply check to see if a
+//! SIGCHLD has happened since we last checked, and while that returns "yes" we
+//! keep trying.
+//!
+//! Note that this means that this isn't really scalable, but then again
+//! processes in general aren't scalable (e.g. millions) so it shouldn't be that
+//! bad in theory...
+
+pub(crate) mod driver;
+
+pub(crate) mod orphan;
+use orphan::{OrphanQueue, OrphanQueueImpl, Wait};
+
+mod reap;
+use reap::Reaper;
+
+use crate::io::PollEvented;
+use crate::process::kill::Kill;
+use crate::process::SpawnedChild;
+use crate::signal::unix::driver::Handle as SignalHandle;
+use crate::signal::unix::{signal, Signal, SignalKind};
+
+use mio::event::Source;
+use mio::unix::SourceFd;
+use once_cell::sync::Lazy;
+use std::fmt;
+use std::fs::File;
+use std::future::Future;
+use std::io;
+use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
+use std::pin::Pin;
+use std::process::{Child as StdChild, ExitStatus, Stdio};
+use std::task::Context;
+use std::task::Poll;
+
+impl Wait for StdChild {
+    fn id(&self) -> u32 {
+        self.id()
+    }
+
+    fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+        self.try_wait()
+    }
+}
+
+impl Kill for StdChild {
+    fn kill(&mut self) -> io::Result<()> {
+        self.kill()
+    }
+}
+
+static ORPHAN_QUEUE: Lazy<OrphanQueueImpl<StdChild>> = Lazy::new(OrphanQueueImpl::new);
+
+pub(crate) struct GlobalOrphanQueue;
+
+impl fmt::Debug for GlobalOrphanQueue {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        ORPHAN_QUEUE.fmt(fmt)
+    }
+}
+
+impl GlobalOrphanQueue {
+    fn reap_orphans(handle: &SignalHandle) {
+        ORPHAN_QUEUE.reap_orphans(handle)
+    }
+}
+
+impl OrphanQueue<StdChild> for GlobalOrphanQueue {
+    fn push_orphan(&self, orphan: StdChild) {
+        ORPHAN_QUEUE.push_orphan(orphan)
+    }
+}
+
+#[must_use = "futures do nothing unless polled"]
+pub(crate) struct Child {
+    inner: Reaper<StdChild, GlobalOrphanQueue, Signal>,
+}
+
+impl fmt::Debug for Child {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("Child")
+            .field("pid", &self.inner.id())
+            .finish()
+    }
+}
+
+pub(crate) fn spawn_child(cmd: &mut std::process::Command) -> io::Result<SpawnedChild> {
+    let mut child = cmd.spawn()?;
+    let stdin = child.stdin.take().map(stdio).transpose()?;
+    let stdout = child.stdout.take().map(stdio).transpose()?;
+    let stderr = child.stderr.take().map(stdio).transpose()?;
+
+    let signal = signal(SignalKind::child())?;
+
+    Ok(SpawnedChild {
+        child: Child {
+            inner: Reaper::new(child, GlobalOrphanQueue, signal),
+        },
+        stdin,
+        stdout,
+        stderr,
+    })
+}
+
+impl Child {
+    pub(crate) fn id(&self) -> u32 {
+        self.inner.id()
+    }
+
+    pub(crate) fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+        self.inner.inner_mut().try_wait()
+    }
+}
+
+impl Kill for Child {
+    fn kill(&mut self) -> io::Result<()> {
+        self.inner.kill()
+    }
+}
+
+impl Future for Child {
+    type Output = io::Result<ExitStatus>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Pin::new(&mut self.inner).poll(cx)
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct Pipe {
+    // Actually a pipe and not a File. However, we are reusing `File` to get
+    // close on drop. This is a similar trick as `mio`.
+    fd: File,
+}
+
+impl<T: IntoRawFd> From<T> for Pipe {
+    fn from(fd: T) -> Self {
+        let fd = unsafe { File::from_raw_fd(fd.into_raw_fd()) };
+        Self { fd }
+    }
+}
+
+impl<'a> io::Read for &'a Pipe {
+    fn read(&mut self, bytes: &mut [u8]) -> io::Result<usize> {
+        (&self.fd).read(bytes)
+    }
+}
+
+impl<'a> io::Write for &'a Pipe {
+    fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
+        (&self.fd).write(bytes)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        (&self.fd).flush()
+    }
+}
+
+impl AsRawFd for Pipe {
+    fn as_raw_fd(&self) -> RawFd {
+        self.fd.as_raw_fd()
+    }
+}
+
+pub(crate) fn convert_to_stdio(io: PollEvented<Pipe>) -> io::Result<Stdio> {
+    let mut fd = io.into_inner()?.fd;
+
+    // Ensure that the fd to be inherited is set to *blocking* mode, as this
+    // is the default that virtually all programs expect to have. Those
+    // programs that know how to work with nonblocking stdio will know how to
+    // change it to nonblocking mode.
+    set_nonblocking(&mut fd, false)?;
+
+    Ok(Stdio::from(fd))
+}
+
+impl Source for Pipe {
+    fn register(
+        &mut self,
+        registry: &mio::Registry,
+        token: mio::Token,
+        interest: mio::Interest,
+    ) -> io::Result<()> {
+        SourceFd(&self.as_raw_fd()).register(registry, token, interest)
+    }
+
+    fn reregister(
+        &mut self,
+        registry: &mio::Registry,
+        token: mio::Token,
+        interest: mio::Interest,
+    ) -> io::Result<()> {
+        SourceFd(&self.as_raw_fd()).reregister(registry, token, interest)
+    }
+
+    fn deregister(&mut self, registry: &mio::Registry) -> io::Result<()> {
+        SourceFd(&self.as_raw_fd()).deregister(registry)
+    }
+}
+
+pub(crate) type ChildStdio = PollEvented<Pipe>;
+
+fn set_nonblocking<T: AsRawFd>(fd: &mut T, nonblocking: bool) -> io::Result<()> {
+    unsafe {
+        let fd = fd.as_raw_fd();
+        let previous = libc::fcntl(fd, libc::F_GETFL);
+        if previous == -1 {
+            return Err(io::Error::last_os_error());
+        }
+
+        let new = if nonblocking {
+            previous | libc::O_NONBLOCK
+        } else {
+            previous & !libc::O_NONBLOCK
+        };
+
+        let r = libc::fcntl(fd, libc::F_SETFL, new);
+        if r == -1 {
+            return Err(io::Error::last_os_error());
+        }
+    }
+
+    Ok(())
+}
+
+pub(super) fn stdio<T>(io: T) -> io::Result<PollEvented<Pipe>>
+where
+    T: IntoRawFd,
+{
+    // Set the fd to nonblocking before we pass it to the event loop
+    let mut pipe = Pipe::from(io);
+    set_nonblocking(&mut pipe, true)?;
+
+    PollEvented::new(pipe)
+}
diff --git a/third_party/rust/tokio/src/process/unix/orphan.rs b/third_party/rust/tokio/src/process/unix/orphan.rs
new file mode 100644
index 0000000000..0e52530c37
--- /dev/null
+++ b/third_party/rust/tokio/src/process/unix/orphan.rs
@@ -0,0 +1,321 @@
+use crate::loom::sync::{Mutex, MutexGuard};
+use crate::signal::unix::driver::Handle as SignalHandle;
+use crate::signal::unix::{signal_with_handle, SignalKind};
+use crate::sync::watch;
+use std::io;
+use std::process::ExitStatus;
+
+/// An interface for waiting on a process to exit.
+pub(crate) trait Wait {
+    /// Get the identifier for this process or diagnostics.
+    fn id(&self) -> u32;
+    /// Try waiting for a process to exit in a non-blocking manner.
+    fn try_wait(&mut self) -> io::Result<Option<ExitStatus>>;
+}
+
+impl<T: Wait> Wait for &mut T {
+    fn id(&self) -> u32 {
+        (**self).id()
+    }
+
+    fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+        (**self).try_wait()
+    }
+}
+
+/// An interface for queueing up an orphaned process so that it can be reaped.
+pub(crate) trait OrphanQueue<T> {
+    /// Adds an orphan to the queue.
+    fn push_orphan(&self, orphan: T);
+}
+
+impl<T, O: OrphanQueue<T>> OrphanQueue<T> for &O {
+    fn push_orphan(&self, orphan: T) {
+        (**self).push_orphan(orphan);
+    }
+}
+
+/// An implementation of `OrphanQueue`.
+#[derive(Debug)]
+pub(crate) struct OrphanQueueImpl<T> {
+    sigchild: Mutex<Option<watch::Receiver<()>>>,
+    queue: Mutex<Vec<T>>,
+}
+
+impl<T> OrphanQueueImpl<T> {
+    pub(crate) fn new() -> Self {
+        Self {
+            sigchild: Mutex::new(None),
+            queue: Mutex::new(Vec::new()),
+        }
+    }
+
+    #[cfg(test)]
+    fn len(&self) -> usize {
+        self.queue.lock().len()
+    }
+
+    pub(crate) fn push_orphan(&self, orphan: T)
+    where
+        T: Wait,
+    {
+        self.queue.lock().push(orphan)
+    }
+
+    /// Attempts to reap every process in the queue, ignoring any errors and
+    /// enqueueing any orphans which have not yet exited.
+    pub(crate) fn reap_orphans(&self, handle: &SignalHandle)
+    where
+        T: Wait,
+    {
+        // If someone else is holding the lock, they will be responsible for draining
+        // the queue as necessary, so we can safely bail if that happens
+        if let Some(mut sigchild_guard) = self.sigchild.try_lock() {
+            match &mut *sigchild_guard {
+                Some(sigchild) => {
+                    if sigchild.try_has_changed().and_then(Result::ok).is_some() {
+                        drain_orphan_queue(self.queue.lock());
+                    }
+                }
+                None => {
+                    let queue = self.queue.lock();
+
+                    // Be lazy and only initialize the SIGCHLD listener if there
+                    // are any orphaned processes in the queue.
+                    if !queue.is_empty() {
+                        // An errors shouldn't really happen here, but if it does it
+                        // means that the signal driver isn't running, in
+                        // which case there isn't anything we can
+                        // register/initialize here, so we can try again later
+                        if let Ok(sigchild) = signal_with_handle(SignalKind::child(), handle) {
+                            *sigchild_guard = Some(sigchild);
+                            drain_orphan_queue(queue);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn drain_orphan_queue<T>(mut queue: MutexGuard<'_, Vec<T>>)
+where
+    T: Wait,
+{
+    for i in (0..queue.len()).rev() {
+        match queue[i].try_wait() {
+            Ok(None) => {}
+            Ok(Some(_)) | Err(_) => {
+                // The stdlib handles interruption errors (EINTR) when polling a child process.
+                // All other errors represent invalid inputs or pids that have already been
+                // reaped, so we can drop the orphan in case an error is raised.
+                queue.swap_remove(i);
+            }
+        }
+    }
+
+    drop(queue);
+}
+
+#[cfg(all(test, not(loom)))]
+pub(crate) mod test {
+    use super::*;
+    use crate::io::driver::Driver as IoDriver;
+    use crate::signal::unix::driver::{Driver as SignalDriver, Handle as SignalHandle};
+    use crate::sync::watch;
+    use std::cell::{Cell, RefCell};
+    use std::io;
+    use std::os::unix::process::ExitStatusExt;
+    use std::process::ExitStatus;
+    use std::rc::Rc;
+
+    pub(crate) struct MockQueue<W> {
+        pub(crate) all_enqueued: RefCell<Vec<W>>,
+    }
+
+    impl<W> MockQueue<W> {
+        pub(crate) fn new() -> Self {
+            Self {
+                all_enqueued: RefCell::new(Vec::new()),
+            }
+        }
+    }
+
+    impl<W> OrphanQueue<W> for MockQueue<W> {
+        fn push_orphan(&self, orphan: W) {
+            self.all_enqueued.borrow_mut().push(orphan);
+        }
+    }
+
+    struct MockWait {
+        total_waits: Rc<Cell<usize>>,
+        num_wait_until_status: usize,
+        return_err: bool,
+    }
+
+    impl MockWait {
+        fn new(num_wait_until_status: usize) -> Self {
+            Self {
+                total_waits: Rc::new(Cell::new(0)),
+                num_wait_until_status,
+                return_err: false,
+            }
+        }
+
+        fn with_err() -> Self {
+            Self {
+                total_waits: Rc::new(Cell::new(0)),
+                num_wait_until_status: 0,
+                return_err: true,
+            }
+        }
+    }
+
+    impl Wait for MockWait {
+        fn id(&self) -> u32 {
+            42
+        }
+
+        fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+            let waits = self.total_waits.get();
+
+            let ret = if self.num_wait_until_status == waits {
+                if self.return_err {
+                    Ok(Some(ExitStatus::from_raw(0)))
+                } else {
+                    Err(io::Error::new(io::ErrorKind::Other, "mock err"))
+                }
+            } else {
+                Ok(None)
+            };
+
+            self.total_waits.set(waits + 1);
+            ret
+        }
+    }
+
+    #[test]
+    fn drain_attempts_a_single_reap_of_all_queued_orphans() {
+        let first_orphan = MockWait::new(0);
+        let second_orphan = MockWait::new(1);
+        let third_orphan = MockWait::new(2);
+        let fourth_orphan = MockWait::with_err();
+
+        let first_waits = first_orphan.total_waits.clone();
+        let second_waits = second_orphan.total_waits.clone();
+        let third_waits = third_orphan.total_waits.clone();
+        let fourth_waits = fourth_orphan.total_waits.clone();
+
+        let orphanage = OrphanQueueImpl::new();
+        orphanage.push_orphan(first_orphan);
+        orphanage.push_orphan(third_orphan);
+        orphanage.push_orphan(second_orphan);
+        orphanage.push_orphan(fourth_orphan);
+
+        assert_eq!(orphanage.len(), 4);
+
+        drain_orphan_queue(orphanage.queue.lock());
+        assert_eq!(orphanage.len(), 2);
+        assert_eq!(first_waits.get(), 1);
+        assert_eq!(second_waits.get(), 1);
+        assert_eq!(third_waits.get(), 1);
+        assert_eq!(fourth_waits.get(), 1);
+
+        drain_orphan_queue(orphanage.queue.lock());
+        assert_eq!(orphanage.len(), 1);
+        assert_eq!(first_waits.get(), 1);
+        assert_eq!(second_waits.get(), 2);
+        assert_eq!(third_waits.get(), 2);
+        assert_eq!(fourth_waits.get(), 1);
+
+        drain_orphan_queue(orphanage.queue.lock());
+        assert_eq!(orphanage.len(), 0);
+        assert_eq!(first_waits.get(), 1);
+        assert_eq!(second_waits.get(), 2);
+        assert_eq!(third_waits.get(), 3);
+        assert_eq!(fourth_waits.get(), 1);
+
+        // Safe to reap when empty
+        drain_orphan_queue(orphanage.queue.lock());
+    }
+
+    #[test]
+    fn no_reap_if_no_signal_received() {
+        let (tx, rx) = watch::channel(());
+
+        let handle = SignalHandle::default();
+
+        let orphanage = OrphanQueueImpl::new();
+        *orphanage.sigchild.lock() = Some(rx);
+
+        let orphan = MockWait::new(2);
+        let waits = orphan.total_waits.clone();
+        orphanage.push_orphan(orphan);
+
+        orphanage.reap_orphans(&handle);
+        assert_eq!(waits.get(), 0);
+
+        orphanage.reap_orphans(&handle);
+        assert_eq!(waits.get(), 0);
+
+        tx.send(()).unwrap();
+        orphanage.reap_orphans(&handle);
+        assert_eq!(waits.get(), 1);
+    }
+
+    #[test]
+    fn no_reap_if_signal_lock_held() {
+        let handle = SignalHandle::default();
+
+        let orphanage = OrphanQueueImpl::new();
+        let signal_guard = orphanage.sigchild.lock();
+
+        let orphan = MockWait::new(2);
+        let waits = orphan.total_waits.clone();
+        orphanage.push_orphan(orphan);
+
+        orphanage.reap_orphans(&handle);
+        assert_eq!(waits.get(), 0);
+
+        drop(signal_guard);
+    }
+
+    #[cfg_attr(miri, ignore)] // Miri does not support epoll.
+    #[test]
+    fn does_not_register_signal_if_queue_empty() {
+        let signal_driver = IoDriver::new().and_then(SignalDriver::new).unwrap();
+        let handle = signal_driver.handle();
+
+        let orphanage = OrphanQueueImpl::new();
+        assert!(orphanage.sigchild.lock().is_none()); // Sanity
+
+        // No register when queue empty
+        orphanage.reap_orphans(&handle);
+        assert!(orphanage.sigchild.lock().is_none());
+
+        let orphan = MockWait::new(2);
+        let waits = orphan.total_waits.clone();
+        orphanage.push_orphan(orphan);
+
+        orphanage.reap_orphans(&handle);
+        assert!(orphanage.sigchild.lock().is_some());
+        assert_eq!(waits.get(), 1); // Eager reap when registering listener
+    }
+
+    #[test]
+    fn does_nothing_if_signal_could_not_be_registered() {
+        let handle = SignalHandle::default();
+
+        let orphanage = OrphanQueueImpl::new();
+        assert!(orphanage.sigchild.lock().is_none());
+
+        let orphan = MockWait::new(2);
+        let waits = orphan.total_waits.clone();
+        orphanage.push_orphan(orphan);
+
+        // Signal handler has "gone away", nothing to register or reap
+        orphanage.reap_orphans(&handle);
+        assert!(orphanage.sigchild.lock().is_none());
+        assert_eq!(waits.get(), 0);
+    }
+}
diff --git a/third_party/rust/tokio/src/process/unix/reap.rs b/third_party/rust/tokio/src/process/unix/reap.rs
new file mode 100644
index 0000000000..f7f4d3cc70
--- /dev/null
+++ b/third_party/rust/tokio/src/process/unix/reap.rs
@@ -0,0 +1,298 @@
+use crate::process::imp::orphan::{OrphanQueue, Wait};
+use crate::process::kill::Kill;
+use crate::signal::unix::InternalStream;
+
+use std::future::Future;
+use std::io;
+use std::ops::Deref;
+use std::pin::Pin;
+use std::process::ExitStatus;
+use std::task::Context;
+use std::task::Poll;
+
+/// Orchestrates between registering interest for receiving signals when a
+/// child process has exited, and attempting to poll for process completion.
+#[derive(Debug)]
+pub(crate) struct Reaper<W, Q, S>
+where
+    W: Wait,
+    Q: OrphanQueue<W>,
+{
+    inner: Option<W>,
+    orphan_queue: Q,
+    signal: S,
+}
+
+impl<W, Q, S> Deref for Reaper<W, Q, S>
+where
+    W: Wait,
+    Q: OrphanQueue<W>,
+{
+    type Target = W;
+
+    fn deref(&self) -> &Self::Target {
+        self.inner()
+    }
+}
+
+impl<W, Q, S> Reaper<W, Q, S>
+where
+    W: Wait,
+    Q: OrphanQueue<W>,
+{
+    pub(crate) fn new(inner: W, orphan_queue: Q, signal: S) -> Self {
+        Self {
+            inner: Some(inner),
+            orphan_queue,
+            signal,
+        }
+    }
+
+    fn inner(&self) -> &W {
+        self.inner.as_ref().expect("inner has gone away")
+    }
+
+    pub(crate) fn inner_mut(&mut self) -> &mut W {
+        self.inner.as_mut().expect("inner has gone away")
+    }
+}
+
+impl<W, Q, S> Future for Reaper<W, Q, S>
+where
+    W: Wait + Unpin,
+    Q: OrphanQueue<W> + Unpin,
+    S: InternalStream + Unpin,
+{
+    type Output = io::Result<ExitStatus>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        loop {
+            // If the child hasn't exited yet, then it's our responsibility to
+            // ensure the current task gets notified when it might be able to
+            // make progress. We can use the delivery of a SIGCHLD signal as a
+            // sign that we can potentially make progress.
+            //
+            // However, we will register for a notification on the next signal
+            // BEFORE we poll the child. Otherwise it is possible that the child
+            // can exit and the signal can arrive after we last polled the child,
+            // but before we've registered for a notification on the next signal
+            // (this can cause a deadlock if there are no more spawned children
+            // which can generate a different signal for us). A side effect of
+            // pre-registering for signal notifications is that when the child
+            // exits, we will have already registered for an additional
+            // notification we don't need to consume. If another signal arrives,
+            // this future's task will be notified/woken up again. Since the
+            // futures model allows for spurious wake ups this extra wakeup
+            // should not cause significant issues with parent futures.
+            let registered_interest = self.signal.poll_recv(cx).is_pending();
+
+            if let Some(status) = self.inner_mut().try_wait()? {
+                return Poll::Ready(Ok(status));
+            }
+
+            // If our attempt to poll for the next signal was not ready, then
+            // we've arranged for our task to get notified and we can bail out.
+            if registered_interest {
+                return Poll::Pending;
+            } else {
+                // Otherwise, if the signal stream delivered a signal to us, we
+                // won't get notified at the next signal, so we'll loop and try
+                // again.
+                continue;
+            }
+        }
+    }
+}
+
+impl<W, Q, S> Kill for Reaper<W, Q, S>
+where
+    W: Kill + Wait,
+    Q: OrphanQueue<W>,
+{
+    fn kill(&mut self) -> io::Result<()> {
+        self.inner_mut().kill()
+    }
+}
+
+impl<W, Q, S> Drop for Reaper<W, Q, S>
+where
+    W: Wait,
+    Q: OrphanQueue<W>,
+{
+    fn drop(&mut self) {
+        if let Ok(Some(_)) = self.inner_mut().try_wait() {
+            return;
+        }
+
+        let orphan = self.inner.take().unwrap();
+        self.orphan_queue.push_orphan(orphan);
+    }
+}
+
+#[cfg(all(test, not(loom)))]
+mod test {
+    use super::*;
+
+    use crate::process::unix::orphan::test::MockQueue;
+    use futures::future::FutureExt;
+    use std::os::unix::process::ExitStatusExt;
+    use std::process::ExitStatus;
+    use std::task::Context;
+    use std::task::Poll;
+
+    #[derive(Debug)]
+    struct MockWait {
+        total_kills: usize,
+        total_waits: usize,
+        num_wait_until_status: usize,
+        status: ExitStatus,
+    }
+
+    impl MockWait {
+        fn new(status: ExitStatus, num_wait_until_status: usize) -> Self {
+            Self {
+                total_kills: 0,
+                total_waits: 0,
+                num_wait_until_status,
+                status,
+            }
+        }
+    }
+
+    impl Wait for MockWait {
+        fn id(&self) -> u32 {
+            0
+        }
+
+        fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+            let ret = if self.num_wait_until_status == self.total_waits {
+                Some(self.status)
+            } else {
+                None
+            };
+
+            self.total_waits += 1;
+            Ok(ret)
+        }
+    }
+
+    impl Kill for MockWait {
+        fn kill(&mut self) -> io::Result<()> {
+            self.total_kills += 1;
+            Ok(())
+        }
+    }
+
+    struct MockStream {
+        total_polls: usize,
+        values: Vec<Option<()>>,
+    }
+
+    impl MockStream {
+        fn new(values: Vec<Option<()>>) -> Self {
+            Self {
+                total_polls: 0,
+                values,
+            }
+        }
+    }
+
+    impl InternalStream for MockStream {
+        fn poll_recv(&mut self, _cx: &mut Context<'_>) -> Poll<Option<()>> {
+            self.total_polls += 1;
+            match self.values.remove(0) {
+                Some(()) => Poll::Ready(Some(())),
+                None => Poll::Pending,
+            }
+        }
+    }
+
+    #[test]
+    fn reaper() {
+        let exit = ExitStatus::from_raw(0);
+        let mock = MockWait::new(exit, 3);
+        let mut grim = Reaper::new(
+            mock,
+            MockQueue::new(),
+            MockStream::new(vec![None, Some(()), None, None, None]),
+        );
+
+        let waker = futures::task::noop_waker();
+        let mut context = Context::from_waker(&waker);
+
+        // Not yet exited, interest registered
+        assert!(grim.poll_unpin(&mut context).is_pending());
+        assert_eq!(1, grim.signal.total_polls);
+        assert_eq!(1, grim.total_waits);
+        assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());
+
+        // Not yet exited, couldn't register interest the first time
+        // but managed to register interest the second time around
+        assert!(grim.poll_unpin(&mut context).is_pending());
+        assert_eq!(3, grim.signal.total_polls);
+        assert_eq!(3, grim.total_waits);
+        assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());
+
+        // Exited
+        if let Poll::Ready(r) = grim.poll_unpin(&mut context) {
+            assert!(r.is_ok());
+            let exit_code = r.unwrap();
+            assert_eq!(exit_code, exit);
+        } else {
+            unreachable!();
+        }
+        assert_eq!(4, grim.signal.total_polls);
+        assert_eq!(4, grim.total_waits);
+        assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());
+    }
+
+    #[test]
+    fn kill() {
+        let exit = ExitStatus::from_raw(0);
+        let mut grim = Reaper::new(
+            MockWait::new(exit, 0),
+            MockQueue::new(),
+            MockStream::new(vec![None]),
+        );
+
+        grim.kill().unwrap();
+        assert_eq!(1, grim.total_kills);
+        assert!(grim.orphan_queue.all_enqueued.borrow().is_empty());
+    }
+
+    #[test]
+    fn drop_reaps_if_possible() {
+        let exit = ExitStatus::from_raw(0);
+        let mut mock = MockWait::new(exit, 0);
+
+        {
+            let queue = MockQueue::new();
+
+            let grim = Reaper::new(&mut mock, &queue, MockStream::new(vec![]));
+
+            drop(grim);
+
+            assert!(queue.all_enqueued.borrow().is_empty());
+        }
+
+        assert_eq!(1, mock.total_waits);
+        assert_eq!(0, mock.total_kills);
+    }
+
+    #[test]
+    fn drop_enqueues_orphan_if_wait_fails() {
+        let exit = ExitStatus::from_raw(0);
+        let mut mock = MockWait::new(exit, 2);
+
+        {
+            let queue = MockQueue::<&mut MockWait>::new();
+            let grim = Reaper::new(&mut mock, &queue, MockStream::new(vec![]));
+            drop(grim);
+
+            assert_eq!(1, queue.all_enqueued.borrow().len());
+        }
+
+        assert_eq!(1, mock.total_waits);
+        assert_eq!(0, mock.total_kills);
+    }
+}
diff --git a/third_party/rust/tokio/src/process/windows.rs b/third_party/rust/tokio/src/process/windows.rs
new file mode 100644
index 0000000000..136d5b0cab
--- /dev/null
+++ b/third_party/rust/tokio/src/process/windows.rs
@@ -0,0 +1,205 @@
+//! Windows asynchronous process handling.
+//!
+//! Like with Unix we don't actually have a way of registering a process with an
+//! IOCP object. As a result we similarly need another mechanism for getting a
+//! signal when a process has exited. For now this is implemented with the
+//! `RegisterWaitForSingleObject` function in the kernel32.dll.
+//!
+//! This strategy is the same that libuv takes and essentially just queues up a
+//! wait for the process in a kernel32-specific thread pool. Once the object is
+//! notified (e.g. the process exits) then we have a callback that basically
+//! just completes a `Oneshot`.
+//!
+//! The `poll_exit` implementation will attempt to wait for the process in a
+//! nonblocking fashion, but failing that it'll fire off a
+//! `RegisterWaitForSingleObject` and then wait on the other end of the oneshot
+//! from then on out.
+
+use crate::io::PollEvented;
+use crate::process::kill::Kill;
+use crate::process::SpawnedChild;
+use crate::sync::oneshot;
+
+use mio::windows::NamedPipe;
+use std::fmt;
+use std::future::Future;
+use std::io;
+use std::os::windows::prelude::{AsRawHandle, FromRawHandle, IntoRawHandle, RawHandle};
+use std::pin::Pin;
+use std::process::Stdio;
+use std::process::{Child as StdChild, Command as StdCommand, ExitStatus};
+use std::ptr;
+use std::task::Context;
+use std::task::Poll;
+use winapi::shared::minwindef::{DWORD, FALSE};
+use winapi::um::handleapi::{DuplicateHandle, INVALID_HANDLE_VALUE};
+use winapi::um::processthreadsapi::GetCurrentProcess;
+use winapi::um::threadpoollegacyapiset::UnregisterWaitEx;
+use winapi::um::winbase::{RegisterWaitForSingleObject, INFINITE};
+use winapi::um::winnt::{
+    BOOLEAN, DUPLICATE_SAME_ACCESS, HANDLE, PVOID, WT_EXECUTEINWAITTHREAD, WT_EXECUTEONLYONCE,
+};
+
+#[must_use = "futures do nothing unless polled"]
+pub(crate) struct Child {
+    child: StdChild,
+    waiting: Option<Waiting>,
+}
+
+impl fmt::Debug for Child {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("Child")
+            .field("pid", &self.id())
+            .field("child", &self.child)
+            .field("waiting", &"..")
+            .finish()
+    }
+}
+
+struct Waiting {
+    rx: oneshot::Receiver<()>,
+    wait_object: HANDLE,
+    tx: *mut Option<oneshot::Sender<()>>,
+}
+
+unsafe impl Sync for Waiting {}
+unsafe impl Send for Waiting {}
+
+pub(crate) fn spawn_child(cmd: &mut StdCommand) -> io::Result<SpawnedChild> {
+    let mut child = cmd.spawn()?;
+    let stdin = child.stdin.take().map(stdio).transpose()?;
+    let stdout = child.stdout.take().map(stdio).transpose()?;
+    let stderr = child.stderr.take().map(stdio).transpose()?;
+
+    Ok(SpawnedChild {
+        child: Child {
+            child,
+            waiting: None,
+        },
+        stdin,
+        stdout,
+        stderr,
+    })
+}
+
+impl Child {
+    pub(crate) fn id(&self) -> u32 {
+        self.child.id()
+    }
+
+    pub(crate) fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
+        self.child.try_wait()
+    }
+}
+
+impl Kill for Child {
+    fn kill(&mut self) -> io::Result<()> {
+        self.child.kill()
+    }
+}
+
+impl Future for Child {
+    type Output = io::Result<ExitStatus>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let inner = Pin::get_mut(self);
+        loop {
+            if let Some(ref mut w) = inner.waiting {
+                match Pin::new(&mut w.rx).poll(cx) {
+                    Poll::Ready(Ok(())) => {}
+                    Poll::Ready(Err(_)) => panic!("should not be canceled"),
+                    Poll::Pending => return Poll::Pending,
+                }
+                let status = inner.try_wait()?.expect("not ready yet");
+                return Poll::Ready(Ok(status));
+            }
+
+            if let Some(e) = inner.try_wait()? {
+                return Poll::Ready(Ok(e));
+            }
+            let (tx, rx) = oneshot::channel();
+            let ptr = Box::into_raw(Box::new(Some(tx)));
+            let mut wait_object = ptr::null_mut();
+            let rc = unsafe {
+                RegisterWaitForSingleObject(
+                    &mut wait_object,
+                    inner.child.as_raw_handle(),
+                    Some(callback),
+                    ptr as *mut _,
+                    INFINITE,
+                    WT_EXECUTEINWAITTHREAD | WT_EXECUTEONLYONCE,
+                )
+            };
+            if rc == 0 {
+                let err = io::Error::last_os_error();
+                drop(unsafe { Box::from_raw(ptr) });
+                return Poll::Ready(Err(err));
+            }
+            inner.waiting = Some(Waiting {
+                rx,
+                wait_object,
+                tx: ptr,
+            });
+        }
+    }
+}
+
+impl AsRawHandle for Child {
+    fn as_raw_handle(&self) -> RawHandle {
+        self.child.as_raw_handle()
+    }
+}
+
+impl Drop for Waiting {
+    fn drop(&mut self) {
+        unsafe {
+            let rc = UnregisterWaitEx(self.wait_object, INVALID_HANDLE_VALUE);
+            if rc == 0 {
+                panic!("failed to unregister: {}", io::Error::last_os_error());
+            }
+            drop(Box::from_raw(self.tx));
+        }
+    }
+}
+
+unsafe extern "system" fn callback(ptr: PVOID, _timer_fired: BOOLEAN) {
+    let complete = &mut *(ptr as *mut Option<oneshot::Sender<()>>);
+    let _ = complete.take().unwrap().send(());
+}
+
+pub(crate) type ChildStdio = PollEvented<NamedPipe>;
+
+pub(super) fn stdio<T>(io: T) -> io::Result<PollEvented<NamedPipe>>
+where
+    T: IntoRawHandle,
+{
+    let pipe = unsafe { NamedPipe::from_raw_handle(io.into_raw_handle()) };
+    PollEvented::new(pipe)
+}
+
+pub(crate) fn convert_to_stdio(io: PollEvented<NamedPipe>) -> io::Result<Stdio> {
+    let named_pipe = io.into_inner()?;
+
+    // Mio does not implement `IntoRawHandle` for `NamedPipe`, so we'll manually
+    // duplicate the handle here...
+    unsafe {
+        let mut dup_handle = INVALID_HANDLE_VALUE;
+        let cur_proc = GetCurrentProcess();
+
+        let status = DuplicateHandle(
+            cur_proc,
+            named_pipe.as_raw_handle(),
+            cur_proc,
+            &mut dup_handle,
+            0 as DWORD,
+            FALSE,
+            DUPLICATE_SAME_ACCESS,
+        );
+
+        if status == 0 {
+            return Err(io::Error::last_os_error());
+        }
+
+        Ok(Stdio::from_raw_handle(dup_handle))
+    }
+}