Import async-global-executor 2.3.1upstream/2.3.1upstream

21 files changed, 1238 insertions, 0 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..90080c7
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "0abe723db4ad440f5cebbd06f95b6234a8116398"
+  },
+  "path_in_vcs": ""
+}
\ No newline at end of file
diff --git a/.github/FUNDING.yml b/.github/FUNDING.yml
new file mode 100644
index 0000000..0f5af72
--- /dev/null
+++ b/.github/FUNDING.yml
@@ -0,0 +1 @@
+github: Keruspe
diff --git a/.github/workflows/build-and-test.yaml b/.github/workflows/build-and-test.yaml
new file mode 100644
index 0000000..3b53331
--- /dev/null
+++ b/.github/workflows/build-and-test.yaml
@@ -0,0 +1,41 @@
+name: Build and test
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  build_and_test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        rust: [nightly, beta, stable, 1.59.0]
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install latest ${{ matrix.rust }}
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: ${{ matrix.rust }}
+            profile: minimal
+            override: true
+
+      - name: Run cargo check
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: --all --bins --examples --tests --all-features
+
+      - name: Run cargo check (without dev-dependencies to catch missing feature flags)
+        if: startsWith(matrix.rust, 'nightly')
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: -Z features=dev_dep
+
+      - name: Run cargo test
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
diff --git a/.github/workflows/lint.yaml b/.github/workflows/lint.yaml
new file mode 100644
index 0000000..1c56821
--- /dev/null
+++ b/.github/workflows/lint.yaml
@@ -0,0 +1,36 @@
+name: Lint
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  clippy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          components: clippy
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --all-features -- -W clippy::all
+
+  rustfmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          components: rustfmt
+      - uses: actions-rs/cargo@v1
+        with:
+          command: fmt
+          args: --all -- --check
diff --git a/.github/workflows/security.yaml b/.github/workflows/security.yaml
new file mode 100644
index 0000000..9890baa
--- /dev/null
+++ b/.github/workflows/security.yaml
@@ -0,0 +1,15 @@
+name: Security audit
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  security_audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
+      - uses: actions-rs/audit-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..96ef6c0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+/target
+Cargo.lock
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..63486dc
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,126 @@
+# Version 2.3.1
+
+- Update blocking dependency
+
+# Version 2.3.0
+
+- Switch back to edition 2021 and MSRV 1.59, dropping num-cups dependency
+
+# Version 2.2.0
+
+- Revert back to edition 2018 and MSRV 1.49
+
+# Version 2.1.0
+
+- Switch from async-mutex to async-lock
+- Switch from num-cpus to Use `std::thread::available_parallelism`
+- Update MSRV to 1.59
+- Update to edition 2021
+
+# Version 2.0.4
+
+- Return concrete type Task from `spawn_blocking`
+
+# Version 2.0.3
+
+- Documentation updates
+
+# Version 2.0.2
+
+- Documentation updates
+
+# Version 2.0.1
+
+- fix build without default features
+
+# Version 2.0.0
+
+- add tokio 1.0 integration
+- rework configuration
+- add a way to update the number of threads at runtime within configured bounds
+
+# Version 1.4.3
+
+- switch to multi threaded tokio schedulers when enabled
+
+# Version 1.4.2
+
+- Drop an Arc
+
+# Version 1.4.1
+
+- switch back to manual implementation for tokio02 integration
+
+# Version 1.4.0
+
+- add tokio03 integration
+
+# Version 1.3.0
+
+- use async-compat for tokio02 integration
+
+# Version 1.2.1
+
+- tokio02 fix
+
+# Version 1.2.0
+
+- Add tokio02 feature
+
+# Version 1.1.1
+
+- Update `async-executor`.
+
+# Version 1.1.0
+
+- Update async-executor
+
+# Version 1.0.2
+
+- Do not run global tasks in `block_on()`
+
+# Version 1.0.1
+
+- Update dependencies
+
+# Version 1.0.0
+
+- Update dependencies
+- Make async-io support optional
+
+# Version 0.2.3
+
+- Change license to MIT or Apache-2.0
+
+# Version 0.2.2
+
+- Reexport `async_executor::Task`
+
+# Version 0.2.1
+
+- Make sure we spawn at least one thread
+
+# Version 0.2.0
+
+- Rename `run` to `block_on` and drop `'static` requirement
+- Add `GlobalExecutorConfig::with_thread_name`
+
+# Version 0.1.4
+
+- Add init functions
+
+# Version 0.1.3
+
+- `run`: do not require `Future` to be `Send`
+
+# Version 0.1.2
+
+- Adjust dependencies
+
+# Versio 0.1.1
+
+- Fix the number of spawned threads
+
+# Version 0.1.0
+
+- Initial release
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..3ff63cb
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,92 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+rust-version = "1.59"
+name = "async-global-executor"
+version = "2.3.1"
+authors = ["Marc-Antoine Perennou <Marc-Antoine@Perennou.com>"]
+description = "A global executor built on top of async-executor and async-io"
+homepage = "https://github.com/Keruspe/async-global-executor"
+documentation = "https://docs.rs/async-global-executor"
+readme = "README.md"
+keywords = [
+    "async",
+    "await",
+    "future",
+    "executor",
+]
+categories = [
+    "asynchronous",
+    "concurrency",
+]
+license = "Apache-2.0 OR MIT"
+repository = "https://github.com/Keruspe/async-global-executor"
+resolver = "2"
+
+[dependencies.async-channel]
+version = "^1.5"
+
+[dependencies.async-executor]
+version = "^1.4"
+
+[dependencies.async-io]
+version = "^1.2"
+optional = true
+
+[dependencies.async-lock]
+version = "^2.5"
+
+[dependencies.blocking]
+version = "^1.2"
+
+[dependencies.futures-lite]
+version = "^1.0"
+
+[dependencies.once_cell]
+version = "^1.4"
+
+[dependencies.tokio-crate]
+version = "^1.0"
+features = [
+    "rt",
+    "rt-multi-thread",
+]
+optional = true
+default-features = false
+package = "tokio"
+
+[dependencies.tokio02-crate]
+version = "^0.2"
+features = ["rt-core"]
+optional = true
+default-features = false
+package = "tokio"
+
+[dependencies.tokio03-crate]
+version = "^0.3.4"
+features = [
+    "rt",
+    "rt-multi-thread",
+]
+optional = true
+default-features = false
+package = "tokio"
+
+[dev-dependencies.doc-comment]
+version = "^0.3"
+
+[features]
+default = ["async-io"]
+tokio = ["tokio-crate"]
+tokio02 = ["tokio02-crate"]
+tokio03 = ["tokio03-crate"]
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..e961706
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,56 @@
+[package]
+name = "async-global-executor"
+version = "2.3.1"
+authors = ["Marc-Antoine Perennou <Marc-Antoine@Perennou.com>"]
+description =  "A global executor built on top of async-executor and async-io"
+edition = "2021"
+license = "Apache-2.0 OR MIT"
+repository = "https://github.com/Keruspe/async-global-executor"
+homepage = "https://github.com/Keruspe/async-global-executor"
+documentation = "https://docs.rs/async-global-executor"
+keywords = ["async", "await", "future", "executor"]
+categories = ["asynchronous", "concurrency"]
+readme = "README.md"
+rust-version = "1.59"
+
+[features]
+default = ["async-io"]
+tokio = ["tokio-crate"]
+tokio02 = ["tokio02-crate"]
+tokio03 = ["tokio03-crate"]
+
+[dependencies]
+async-channel = "^1.5"
+async-executor = "^1.4"
+async-lock = "^2.5"
+blocking = "^1.2"
+futures-lite = "^1.0"
+once_cell = "^1.4"
+
+[dependencies.async-io]
+version = "^1.2"
+optional = true
+
+[dependencies.tokio-crate]
+package = "tokio"
+version = "^1.0"
+optional = true
+default-features = false
+features = ["rt", "rt-multi-thread"]
+
+[dependencies.tokio02-crate]
+package = "tokio"
+version = "^0.2"
+optional = true
+default-features = false
+features = ["rt-core"]
+
+[dependencies.tokio03-crate]
+package = "tokio"
+version = "^0.3.4"
+optional = true
+default-features = false
+features = ["rt", "rt-multi-thread"]
+
+[dev-dependencies]
+doc-comment = "^0.3"
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..31aa793
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
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+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a1e210a
--- /dev/null
+++ b/README.md
@@ -0,0 +1,55 @@
+# async-global-executor
+
+[![API Docs](https://docs.rs/async-global-executor/badge.svg)](https://docs.rs/async-global-executor)
+[![Build status](https://github.com/Keruspe/async-global-executor/workflows/Build%20and%20test/badge.svg)](https://github.com/Keruspe/async-global-executor/actions)
+[![Downloads](https://img.shields.io/crates/d/async-global-executor.svg)](https://crates.io/crates/async-global-executor)
+
+A global executor built on top of async-executor and async-io
+
+# Features
+
+* `async-io`: if enabled, `async-global-executor` will use `async_io::block_on` instead of
+  `futures_lite::future::block_on` internally. this is preferred if your application also uses `async-io`.
+* `blocking`: enable the use of the `blocking` crate through `async_global_executor::spawn_blocking`.
+* `tokio`: if enabled, `async-global-executor` will ensure that all tasks that you will spawn run in the context of a
+  tokio 1.0 runtime, spawning a new one if required.
+* `tokio03`: if enabled, `async-global-executor` will ensure that all tasks that you will spawn run in the context of a
+  tokio 0.3 runtime, spawning a new one if required.
+* `tokio02`: if enabled, `async-global-executor` will ensure that all tasks that you will spawn run in the context of a
+  tokio 0.2 runtime, spawning a new one if required.
+
+# Examples
+
+```
+# use futures_lite::future;
+
+// spawn a task on the multi-threaded executor
+let task1 = async_global_executor::spawn(async {
+    1 + 2
+});
+// spawn a task on the local executor (same thread)
+let task2 = async_global_executor::spawn_local(async {
+    3 + 4
+});
+let task = future::zip(task1, task2);
+
+// run the executor
+async_global_executor::block_on(async {
+    assert_eq!(task.await, (3, 7));
+});
+```
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+#### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
diff --git a/src/config.rs b/src/config.rs
new file mode 100644
index 0000000..45048ab
--- /dev/null
+++ b/src/config.rs
@@ -0,0 +1,97 @@
+use once_cell::sync::OnceCell;
+use std::{
+    fmt,
+    sync::atomic::{AtomicUsize, Ordering},
+};
+
+pub(crate) static GLOBAL_EXECUTOR_CONFIG: OnceCell<Config> = OnceCell::new();
+
+/// Configuration to init the thread pool for the multi-threaded global executor.
+#[derive(Default)]
+pub struct GlobalExecutorConfig {
+    /// The environment variable from which we'll try to parse the number of threads to spawn.
+    env_var: Option<&'static str>,
+    /// The minimum number of threads to spawn.
+    min_threads: Option<usize>,
+    /// The maximum number of threads to spawn.
+    max_threads: Option<usize>,
+    /// The closure function used to get the name of the thread. The name can be used for identification in panic messages.
+    thread_name_fn: Option<Box<dyn Fn() -> String + Send + Sync>>,
+}
+
+impl fmt::Debug for GlobalExecutorConfig {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("GlobalExecutorConfig")
+            .field("env_var", &self.env_var)
+            .field("min_threads", &self.min_threads)
+            .field("max_threads", &self.max_threads)
+            .finish()
+    }
+}
+
+impl GlobalExecutorConfig {
+    /// Use the specified environment variable to find the number of threads to spawn.
+    pub fn with_env_var(mut self, env_var: &'static str) -> Self {
+        self.env_var = Some(env_var);
+        self
+    }
+
+    /// Use the specified value as the minimum number of threads.
+    pub fn with_min_threads(mut self, min_threads: usize) -> Self {
+        self.min_threads = Some(min_threads);
+        self
+    }
+
+    /// Use the specified value as the maximum number of threads for async tasks.
+    /// To limit the maximum number of threads for blocking tasks, please use the
+    /// `BLOCKING_MAX_THREADS` environment variable.
+    pub fn with_max_threads(mut self, max_threads: usize) -> Self {
+        self.max_threads = Some(max_threads);
+        self
+    }
+
+    /// Use the specified prefix to name the threads.
+    pub fn with_thread_name_fn(
+        mut self,
+        thread_name_fn: impl Fn() -> String + Send + Sync + 'static,
+    ) -> Self {
+        self.thread_name_fn = Some(Box::new(thread_name_fn));
+        self
+    }
+
+    pub(crate) fn seal(self) -> Config {
+        let min_threads = std::env::var(self.env_var.unwrap_or("ASYNC_GLOBAL_EXECUTOR_THREADS"))
+            .ok()
+            .and_then(|threads| threads.parse().ok())
+            .or(self.min_threads)
+            .unwrap_or_else(|| std::thread::available_parallelism().map_or(1, usize::from))
+            .max(1);
+        let max_threads = self.max_threads.unwrap_or(min_threads * 4).max(min_threads);
+        Config {
+            min_threads,
+            max_threads,
+            thread_name_fn: self.thread_name_fn.unwrap_or_else(|| {
+                Box::new(|| {
+                    static GLOBAL_EXECUTOR_NEXT_THREAD: AtomicUsize = AtomicUsize::new(1);
+                    format!(
+                        "async-global-executor-{}",
+                        GLOBAL_EXECUTOR_NEXT_THREAD.fetch_add(1, Ordering::SeqCst)
+                    )
+                })
+            }),
+        }
+    }
+}
+
+// The actual configuration, computed from the given GlobalExecutorConfig
+pub(crate) struct Config {
+    pub(crate) min_threads: usize,
+    pub(crate) max_threads: usize,
+    pub(crate) thread_name_fn: Box<dyn Fn() -> String + Send + Sync>,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        GlobalExecutorConfig::default().seal()
+    }
+}
diff --git a/src/executor.rs b/src/executor.rs
new file mode 100644
index 0000000..838fbd6
--- /dev/null
+++ b/src/executor.rs
@@ -0,0 +1,102 @@
+use crate::Task;
+use async_executor::{Executor, LocalExecutor};
+use std::future::Future;
+
+pub(crate) static GLOBAL_EXECUTOR: Executor<'_> = Executor::new();
+
+thread_local! {
+    pub(crate) static LOCAL_EXECUTOR: LocalExecutor<'static> = LocalExecutor::new();
+}
+
+/// Runs the global and the local executor on the current thread
+///
+/// Note: this calls `async_io::block_on` underneath.
+///
+/// # Examples
+///
+/// ```
+/// let task = async_global_executor::spawn(async {
+///     1 + 2
+/// });
+/// async_global_executor::block_on(async {
+///     assert_eq!(task.await, 3);
+/// });
+/// ```
+pub fn block_on<F: Future<Output = T>, T>(future: F) -> T {
+    LOCAL_EXECUTOR.with(|executor| crate::reactor::block_on(executor.run(future)))
+}
+
+/// Spawns a task onto the multi-threaded global executor.
+///
+/// # Examples
+///
+/// ```
+/// # use futures_lite::future;
+///
+/// let task1 = async_global_executor::spawn(async {
+///     1 + 2
+/// });
+/// let task2 = async_global_executor::spawn(async {
+///     3 + 4
+/// });
+/// let task = future::zip(task1, task2);
+///
+/// async_global_executor::block_on(async {
+///     assert_eq!(task.await, (3, 7));
+/// });
+/// ```
+pub fn spawn<F: Future<Output = T> + Send + 'static, T: Send + 'static>(future: F) -> Task<T> {
+    crate::init();
+    GLOBAL_EXECUTOR.spawn(future)
+}
+
+/// Spawns a task onto the local executor.
+///
+///
+/// The task does not need to be `Send` as it will be spawned on the same thread.
+///
+/// # Examples
+///
+/// ```
+/// # use futures_lite::future;
+///
+/// let task1 = async_global_executor::spawn_local(async {
+///     1 + 2
+/// });
+/// let task2 = async_global_executor::spawn_local(async {
+///     3 + 4
+/// });
+/// let task = future::zip(task1, task2);
+///
+/// async_global_executor::block_on(async {
+///     assert_eq!(task.await, (3, 7));
+/// });
+/// ```
+pub fn spawn_local<F: Future<Output = T> + 'static, T: 'static>(future: F) -> Task<T> {
+    LOCAL_EXECUTOR.with(|executor| executor.spawn(future))
+}
+
+/// Runs blocking code on a thread pool.
+///
+/// # Examples
+///
+/// Read the contents of a file:
+///
+/// ```no_run
+/// # async_global_executor::block_on(async {
+/// let contents = async_global_executor::spawn_blocking(|| std::fs::read_to_string("file.txt")).await?;
+/// # std::io::Result::Ok(()) });
+/// ```
+///
+/// Spawn a process:
+///
+/// ```no_run
+/// use std::process::Command;
+///
+/// # async_global_executor::block_on(async {
+/// let out = async_global_executor::spawn_blocking(|| Command::new("dir").output()).await?;
+/// # std::io::Result::Ok(()) });
+/// ```
+pub fn spawn_blocking<F: FnOnce() -> T + Send + 'static, T: Send + 'static>(f: F) -> Task<T> {
+    blocking::unblock(f)
+}
diff --git a/src/init.rs b/src/init.rs
new file mode 100644
index 0000000..b32b388
--- /dev/null
+++ b/src/init.rs
@@ -0,0 +1,42 @@
+use std::sync::atomic::{AtomicBool, Ordering};
+
+/// Init the global executor, spawning as many threads as specified or
+/// the value specified by the specified environment variable.
+///
+/// # Examples
+///
+/// ```
+/// async_global_executor::init_with_config(
+///     async_global_executor::GlobalExecutorConfig::default()
+///         .with_env_var("NUMBER_OF_THREADS")
+///         .with_min_threads(4)
+///         .with_max_threads(6)
+///         .with_thread_name_fn(Box::new(|| "worker".to_string()))
+/// );
+/// ```
+pub fn init_with_config(config: crate::config::GlobalExecutorConfig) {
+    let _ = crate::config::GLOBAL_EXECUTOR_CONFIG.set(config.seal());
+    init();
+}
+
+/// Init the global executor, spawning as many threads as the number or cpus or
+/// the value specified by the `ASYNC_GLOBAL_EXECUTOR_THREADS` environment variable
+/// if specified.
+///
+/// # Examples
+///
+/// ```
+/// async_global_executor::init();
+/// ```
+pub fn init() {
+    static INIT_DONE: AtomicBool = AtomicBool::new(false);
+    if !INIT_DONE.swap(true, Ordering::SeqCst) {
+        let config =
+            crate::config::GLOBAL_EXECUTOR_CONFIG.get_or_init(crate::config::Config::default);
+        crate::reactor::block_on(async {
+            crate::threading::spawn_more_threads(config.min_threads)
+                .await
+                .expect("cannot spawn executor threads");
+        });
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..0900941
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,51 @@
+//! A global executor built on top of async-executor and async_io
+//!
+//! The global executor is lazily spawned on first use. It spawns as many threads
+//! as the number of cpus by default. You can override this using the
+//! `ASYNC_GLOBAL_EXECUTOR_THREADS` environment variable.
+//!
+//! # Examples
+//!
+//! ```
+//! # use futures_lite::future;
+//!
+//! // spawn a task on the multi-threaded executor
+//! let task1 = async_global_executor::spawn(async {
+//!     1 + 2
+//! });
+//! // spawn a task on the local executor (same thread)
+//! let task2 = async_global_executor::spawn_local(async {
+//!     3 + 4
+//! });
+//! let task = future::zip(task1, task2);
+//!
+//! // run the executor
+//! async_global_executor::block_on(async {
+//!     assert_eq!(task.await, (3, 7));
+//! });
+//! ```
+
+#![forbid(unsafe_code)]
+#![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+
+#[cfg(doctest)]
+doc_comment::doctest!("../README.md");
+
+pub use async_executor::Task;
+pub use config::GlobalExecutorConfig;
+pub use executor::{block_on, spawn, spawn_blocking, spawn_local};
+pub use init::{init, init_with_config};
+pub use threading::{spawn_more_threads, stop_current_thread, stop_thread};
+
+mod config;
+mod executor;
+mod init;
+mod reactor;
+mod threading;
+
+#[cfg(feature = "tokio")]
+mod tokio;
+#[cfg(feature = "tokio02")]
+mod tokio02;
+#[cfg(feature = "tokio03")]
+mod tokio03;
diff --git a/src/reactor.rs b/src/reactor.rs
new file mode 100644
index 0000000..090e1a7
--- /dev/null
+++ b/src/reactor.rs
@@ -0,0 +1,13 @@
+pub(crate) fn block_on<F: std::future::Future<Output = T>, T>(future: F) -> T {
+    #[cfg(feature = "async-io")]
+    let run = || async_io::block_on(future);
+    #[cfg(not(feature = "async-io"))]
+    let run = || futures_lite::future::block_on(future);
+    #[cfg(feature = "tokio")]
+    let _tokio_enter = crate::tokio::enter();
+    #[cfg(feature = "tokio02")]
+    let run = || crate::tokio02::enter(run);
+    #[cfg(feature = "tokio03")]
+    let _tokio03_enter = crate::tokio03::enter();
+    run()
+}
diff --git a/src/threading.rs b/src/threading.rs
new file mode 100644
index 0000000..ed8b549
--- /dev/null
+++ b/src/threading.rs
@@ -0,0 +1,156 @@
+use crate::Task;
+use async_channel::{Receiver, Sender};
+use async_lock::Mutex;
+use futures_lite::future;
+use once_cell::sync::OnceCell;
+use std::{io, thread};
+
+// The current number of threads (some might be shutting down and not in the pool anymore)
+static GLOBAL_EXECUTOR_THREADS_NUMBER: Mutex<usize> = Mutex::new(0);
+// The expected number of threads (excluding the one that are shutting down)
+static GLOBAL_EXECUTOR_EXPECTED_THREADS_NUMBER: Mutex<usize> = Mutex::new(0);
+
+thread_local! {
+    // Used to shutdown a thread when we receive a message from the Sender.
+    // We send an ack using to the Receiver once we're finished shutting down.
+    static THREAD_SHUTDOWN: OnceCell<(Sender<()>, Receiver<()>)> = OnceCell::new();
+}
+
+/// Spawn more executor threads, up to configured max value.
+///
+/// Returns how many threads we spawned.
+///
+/// # Examples
+///
+/// ```
+/// async_global_executor::spawn_more_threads(2);
+/// ```
+pub async fn spawn_more_threads(count: usize) -> io::Result<usize> {
+    // Get the current configuration, or initialize the thread pool.
+    let config = crate::config::GLOBAL_EXECUTOR_CONFIG
+        .get()
+        .unwrap_or_else(|| {
+            crate::init();
+            crate::config::GLOBAL_EXECUTOR_CONFIG.get().unwrap()
+        });
+    // How many threads do we have (including shutting down)
+    let mut threads_number = GLOBAL_EXECUTOR_THREADS_NUMBER.lock().await;
+    // How many threads are we supposed to have (when all shutdowns are complete)
+    let mut expected_threads_number = GLOBAL_EXECUTOR_EXPECTED_THREADS_NUMBER.lock().await;
+    // Ensure we don't exceed configured max threads (including shutting down)
+    let count = count.min(config.max_threads - *threads_number);
+    for _ in 0..count {
+        thread::Builder::new()
+            .name((config.thread_name_fn)())
+            .spawn(thread_main_loop)?;
+        *threads_number += 1;
+        *expected_threads_number += 1;
+    }
+    Ok(count)
+}
+
+/// Stop one of the executor threads, down to configured min value
+///
+/// Returns whether a thread has been stopped.
+///
+/// # Examples
+///
+/// ```
+/// async_global_executor::stop_thread();
+/// ```
+pub fn stop_thread() -> Task<bool> {
+    crate::spawn(stop_current_executor_thread())
+}
+
+/// Stop the current executor thread, if we exceed the configured min value
+///
+/// Returns whether the thread has been stopped.
+///
+/// # Examples
+///
+/// ```
+/// async_global_executor::stop_current_thread();
+/// ```
+pub fn stop_current_thread() -> Task<bool> {
+    crate::spawn_local(stop_current_executor_thread())
+}
+
+fn thread_main_loop() {
+    // This will be used to ask for shutdown.
+    let (s, r) = async_channel::bounded(1);
+    // This wil be used to ack once shutdown is complete.
+    let (s_ack, r_ack) = async_channel::bounded(1);
+    THREAD_SHUTDOWN.with(|thread_shutdown| drop(thread_shutdown.set((s, r_ack))));
+
+    // Main loop
+    loop {
+        #[allow(clippy::blocks_in_if_conditions)]
+        if std::panic::catch_unwind(|| {
+            crate::executor::LOCAL_EXECUTOR.with(|executor| {
+                let local = executor.run(async {
+                    // Wait until we're asked to shutdown.
+                    let _ = r.recv().await;
+                });
+                let global = crate::executor::GLOBAL_EXECUTOR.run(future::pending::<()>());
+                crate::reactor::block_on(future::or(local, global));
+            });
+        })
+        .is_ok()
+        {
+            break;
+        }
+    }
+
+    wait_for_local_executor_completion();
+
+    // Ack that we're done shutting down.
+    crate::reactor::block_on(async {
+        let _ = s_ack.send(()).await;
+    });
+}
+
+fn wait_for_local_executor_completion() {
+    loop {
+        #[allow(clippy::blocks_in_if_conditions)]
+        if std::panic::catch_unwind(|| {
+            crate::executor::LOCAL_EXECUTOR.with(|executor| {
+                crate::reactor::block_on(async {
+                    // Wait for spawned tasks completion
+                    while !executor.is_empty() {
+                        executor.tick().await;
+                    }
+                });
+            });
+        })
+        .is_ok()
+        {
+            break;
+        }
+    }
+}
+
+async fn stop_current_executor_thread() -> bool {
+    // How many threads are we supposed to have (when all shutdowns are complete)
+    let mut expected_threads_number = GLOBAL_EXECUTOR_EXPECTED_THREADS_NUMBER.lock().await;
+    // Ensure we don't go below the configured min_threads (ignoring shutting down)
+    if *expected_threads_number
+        > crate::config::GLOBAL_EXECUTOR_CONFIG
+            .get()
+            .unwrap()
+            .min_threads
+    {
+        let (s, r_ack) =
+            THREAD_SHUTDOWN.with(|thread_shutdown| thread_shutdown.get().unwrap().clone());
+        let _ = s.send(()).await;
+        // We now expect to have one less thread (this one is shutting down)
+        *expected_threads_number -= 1;
+        // Unlock the Mutex
+        drop(expected_threads_number);
+        let _ = r_ack.recv().await;
+        // This thread is done shutting down
+        *GLOBAL_EXECUTOR_THREADS_NUMBER.lock().await -= 1;
+        true
+    } else {
+        false
+    }
+}
diff --git a/src/tokio.rs b/src/tokio.rs
new file mode 100644
index 0000000..a594640
--- /dev/null
+++ b/src/tokio.rs
@@ -0,0 +1,41 @@
+use once_cell::sync::Lazy;
+use tokio_crate as tokio;
+
+pub(crate) fn enter() -> tokio::runtime::EnterGuard<'static> {
+    RUNTIME.enter()
+}
+
+static RUNTIME: Lazy<tokio::runtime::Handle> = Lazy::new(|| {
+    tokio::runtime::Handle::try_current().unwrap_or_else(|_| {
+        let rt = tokio::runtime::Runtime::new().expect("failed to build tokio runtime");
+        let handle = rt.handle().clone();
+        std::thread::Builder::new()
+            .name("async-global-executor/tokio".to_string())
+            .spawn(move || {
+                rt.block_on(futures_lite::future::pending::<()>());
+            })
+            .expect("failed to spawn tokio driver thread");
+        handle
+    })
+});
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    async fn compute() -> u8 {
+        tokio::spawn(async { 1 + 2 }).await.unwrap()
+    }
+
+    #[test]
+    fn spawn_tokio() {
+        crate::block_on(async {
+            assert_eq!(
+                crate::spawn(compute()).await
+                    + crate::spawn_local(compute()).await
+                    + tokio::spawn(compute()).await.unwrap(),
+                9
+            );
+        });
+    }
+}
diff --git a/src/tokio02.rs b/src/tokio02.rs
new file mode 100644
index 0000000..d4ff571
--- /dev/null
+++ b/src/tokio02.rs
@@ -0,0 +1,41 @@
+use once_cell::sync::Lazy;
+use tokio02_crate as tokio;
+
+pub(crate) fn enter<F: FnOnce() -> R, R>(f: F) -> R {
+    RUNTIME.enter(f)
+}
+
+static RUNTIME: Lazy<tokio::runtime::Handle> = Lazy::new(|| {
+    tokio::runtime::Handle::try_current().unwrap_or_else(|_| {
+        let mut rt = tokio::runtime::Runtime::new().expect("failed to build tokio02 runtime");
+        let handle = rt.handle().clone();
+        std::thread::Builder::new()
+            .name("async-global-executor/tokio02".to_string())
+            .spawn(move || {
+                rt.block_on(futures_lite::future::pending::<()>());
+            })
+            .expect("failed to spawn tokio02 driver thread");
+        handle
+    })
+});
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    async fn compute() -> u8 {
+        tokio::spawn(async { 1 + 2 }).await.unwrap()
+    }
+
+    #[test]
+    fn spawn_tokio() {
+        crate::block_on(async {
+            assert_eq!(
+                crate::spawn(compute()).await
+                    + crate::spawn_local(compute()).await
+                    + tokio::spawn(compute()).await.unwrap(),
+                9
+            );
+        });
+    }
+}
diff --git a/src/tokio03.rs b/src/tokio03.rs
new file mode 100644
index 0000000..67a1ce7
--- /dev/null
+++ b/src/tokio03.rs
@@ -0,0 +1,41 @@
+use once_cell::sync::Lazy;
+use tokio03_crate as tokio;
+
+pub(crate) fn enter() -> tokio::runtime::EnterGuard<'static> {
+    RUNTIME.enter()
+}
+
+static RUNTIME: Lazy<tokio::runtime::Handle> = Lazy::new(|| {
+    tokio::runtime::Handle::try_current().unwrap_or_else(|_| {
+        let rt = tokio::runtime::Runtime::new().expect("failed to build tokio03 runtime");
+        let handle = rt.handle().clone();
+        std::thread::Builder::new()
+            .name("async-global-executor/tokio03".to_string())
+            .spawn(move || {
+                rt.block_on(futures_lite::future::pending::<()>());
+            })
+            .expect("failed to spawn tokio03 driver thread");
+        handle
+    })
+});
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    async fn compute() -> u8 {
+        tokio::spawn(async { 1 + 2 }).await.unwrap()
+    }
+
+    #[test]
+    fn spawn_tokio() {
+        crate::block_on(async {
+            assert_eq!(
+                crate::spawn(compute()).await
+                    + crate::spawn_local(compute()).await
+                    + tokio::spawn(compute()).await.unwrap(),
+                9
+            );
+        });
+    }
+}