Add async tasks support

Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>

Cargo.lock

@@ -2,6 +2,12 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
 [[package]]
 name = "bit_field"
 version = "0.10.1"
@@ -20,10 +26,79 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "cfg-if"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
+[[package]]
+name = "conquer-once"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96eb12fb69466716fbae9009d389e6a30830ae8975e170eff2d2cff579f9efa3"
+dependencies = [
+ "conquer-util",
+]
+
+[[package]]
+name = "conquer-util"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
+
+[[package]]
+name = "crossbeam-queue"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "774ba60a54c213d409d5353bda12d49cd68d14e45036a285234c8d6f91f92570"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+ "maybe-uninit",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
+dependencies = [
+ "autocfg",
+ "cfg-if",
+]
+
+[[package]]
+name = "futures-core"
+version = "0.3.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04909a7a7e4633ae6c4a9ab280aeb86da1236243a77b694a49eacd659a4bd3ac"
+
+[[package]]
+name = "futures-task"
+version = "0.3.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ffb393ac5d9a6eaa9d3fdf37ae2776656b706e200c8e16b1bdb227f5198e6ea"
+
+[[package]]
+name = "futures-util"
+version = "0.3.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "197676987abd2f9cadff84926f410af1c183608d36641465df73ae8211dc65d6"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "pin-project-lite",
+ "pin-utils",
+]
+
 [[package]]
 name = "julios"
 version = "0.1.0"
 dependencies = [
+ "conquer-once",
+ "crossbeam-queue",
+ "futures-util",
  "lazy_static",
  "linked_list_allocator",
  "multiboot2",
@@ -61,6 +136,12 @@ dependencies = [
  "scopeguard",
 ]
 
+[[package]]
+name = "maybe-uninit"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60302e4db3a61da70c0cb7991976248362f30319e88850c487b9b95bbf059e00"
+
 [[package]]
 name = "multiboot2"
 version = "0.1.0"
@@ -85,6 +166,18 @@ dependencies = [
  "x86_64",
 ]
 
+[[package]]
+name = "pin-project-lite"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e0a7ae3ac2f1173085d398531c705756c94a4c56843785df85a60c1a0afac116"
+
+[[package]]
+name = "pin-utils"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
+
 [[package]]
 name = "rustversion"
 version = "1.0.6"

Cargo.toml

@@ -20,3 +20,17 @@ linked_list_allocator = "0.9.0"
 [dependencies.lazy_static]
 version = "1.0"
 features = ["spin_no_std"]
+
+[dependencies.crossbeam-queue]
+version = "0.2.1"
+default-features = false
+features = ["alloc"]
+
+[dependencies.conquer-once]
+version = "0.2.0"
+default-features = false
+
+[dependencies.futures-util]
+version = "0.3.4"
+default-features = false
+features = ["alloc"]

src/interrupts/pic/keyboard.rs

@@ -1,32 +1,16 @@
-use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
-use lazy_static::lazy_static;
 use super::{PICS, InterruptIndex};
+
 use x86_64::instructions::port::Port;
-use spin::{self, Mutex};
-use crate::{print};
 use x86_64::structures::idt::{InterruptStackFrame};
 
 pub const PS2_CONTROLLER_PORT: u16 = 0x60;
 
 pub extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: InterruptStackFrame) {
-    lazy_static! {
-        static ref KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet1>> = Mutex::new(
-            Keyboard::new(layouts::Us104Key, ScancodeSet1, HandleControl::Ignore)
-        );
-    }
-
-    let mut keyboard = KEYBOARD.lock();
     let mut port = Port::new(PS2_CONTROLLER_PORT);
     let scancode: u8 = unsafe { port.read() };
 
-    if let Ok(Some(key_event)) = keyboard.add_byte(scancode) {
-        if let Some(key) = keyboard.process_keyevent(key_event) {
-            match key {
-                DecodedKey::Unicode(character) => print!("{}", character),
-                DecodedKey::RawKey(key) => print!("{:?}", key),
-            }
-        }
-    }
+    crate::task::keyboard::add_scancode(scancode);
+
     unsafe {
         PICS.lock()
             .notify_end_of_interrupt(InterruptIndex::Keyboard.as_u8());

src/lib.rs

@@ -8,6 +8,7 @@ mod interrupts;
 mod memory;
 mod serial;
 mod vga;
+mod task;
 
 //#[macro_use]
 extern crate alloc;
@@ -16,6 +17,7 @@ extern crate multiboot2;
 use core::panic::PanicInfo;
 use multiboot2::BootInformation;
 use vga::{Color, ColorCode};
+use task::{executor::Executor, Task, keyboard};
 
 #[alloc_error_handler]
 fn alloc_error_handler(layout: alloc::alloc::Layout) -> ! {
@@ -53,8 +55,7 @@ pub extern "C" fn julios_main(multiboot_info_addr: usize) -> ! {
     println!("***JuliOS V0.1.0***");
     serial_println!("Hello serial");
 
-    use alloc::boxed::Box;
-    let x = Box::new(41);
-
-    panic!("Kernel end of flow");
+    let mut executor = Executor::new();
+    executor.spawn(Task::new(keyboard::print_keypresses()));
+    executor.run();
 }

src/task/executor.rs

@@ -0,0 +1,101 @@
+use super::{Task, TaskId};
+use alloc::{collections::BTreeMap, sync::Arc, task::Wake};
+use core::task::{Context, Poll, Waker};
+use crossbeam_queue::ArrayQueue;
+
+pub struct Executor {
+    tasks: BTreeMap<TaskId, Task>,
+    task_queue: Arc<ArrayQueue<TaskId>>,
+    waker_cache: BTreeMap<TaskId, Waker>
+}
+
+impl Executor {
+    pub fn new() -> Self {
+        Executor {
+            tasks: BTreeMap::new(),
+            task_queue: Arc::new(ArrayQueue::new(100)),
+            waker_cache: BTreeMap::new()
+        }
+    }
+
+    pub fn run(&mut self) -> ! {
+        loop {
+            self.run_ready_tasks();
+            self.sleep_if_idle();
+        }
+    }
+
+    fn sleep_if_idle(&self) {
+        use x86_64::instructions::interrupts::{self, enable_and_hlt};
+        interrupts::disable();
+
+        if self.task_queue.is_empty() {
+            enable_and_hlt();
+        } else {
+            interrupts::enable();
+        }
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        let task_id = task.id;
+        if self.tasks.insert(task.id, task).is_some() {
+            panic!("Duplicate task ID");
+        }
+        self.task_queue.push(task_id).expect("Task queue full");
+    }
+
+    fn run_ready_tasks(&mut self) {
+        let Self {
+            tasks,
+            task_queue,
+            waker_cache
+        } = self; // Executor destructuring
+
+        while let Ok(task_id) = task_queue.pop() {
+            let task = match tasks.get_mut(&task_id) {
+                Some(task) => task,
+                None => continue, // Task does not exist anymore
+            };
+            let waker = waker_cache
+                .entry(task_id)
+                .or_insert_with(|| TaskWaker::new(task_id, task_queue.clone()));
+            let mut context = Context::from_waker(waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {
+                    // task is done
+                    tasks.remove(&task_id);
+                    waker_cache.remove(&task_id);
+                }
+                Poll::Pending => {}
+            }
+        }
+    }
+}
+
+struct TaskWaker {
+    task_id: TaskId,
+    task_queue: Arc<ArrayQueue<TaskId>>
+}
+
+impl TaskWaker {
+    fn new(task_id: TaskId, task_queue: Arc<ArrayQueue<TaskId>>) -> Waker {
+        Waker::from(Arc::new(TaskWaker {
+            task_id,
+            task_queue
+        }))
+    }
+
+    fn wake_task(&self) {
+        self.task_queue.push(self.task_id).expect("Task queue full");
+    }
+}
+
+impl Wake for TaskWaker {
+    fn wake(self: Arc<Self>) {
+        self.wake_task();
+    }
+
+    fn wake_by_ref(self: &Arc<Self>) {
+        self.wake_task();
+    }
+}

src/task/keyboard.rs

@@ -0,0 +1,80 @@
+use crate::{println, print};
+
+use conquer_once::spin::OnceCell;
+use core::{pin::Pin, task::{Context, Poll}};
+use crossbeam_queue::ArrayQueue;
+use futures_util::task::AtomicWaker;
+use futures_util::stream::{Stream, StreamExt};
+use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
+
+static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
+
+static WAKER: AtomicWaker = AtomicWaker::new();
+
+pub struct ScancodeStream {
+    _private: (), // Makes ScancodeStream constructable only
+                  // inside the module with ScancodeStream::new()
+}
+
+impl ScancodeStream {
+    pub fn new() -> Self {
+        SCANCODE_QUEUE.try_init_once(|| ArrayQueue::new(100))
+            .expect("ScancodeStream::new should only be called once");
+        ScancodeStream { _private: () }
+    }
+}
+
+impl Stream for ScancodeStream {
+    type Item = u8;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<u8>> {
+        let queue = SCANCODE_QUEUE
+            .try_get()
+            .expect("Keyboard scancode queue not initialized");
+
+        if let Ok(scancode) = queue.pop() {
+            return Poll::Ready(Some(scancode));
+        }
+
+        WAKER.register(&cx.waker());
+
+        match queue.pop() {
+            Ok(scancode) => {
+                WAKER.take();
+                Poll::Ready(Some(scancode))
+            },
+            Err(crossbeam_queue::PopError) => Poll::Pending
+        }
+    }
+}
+
+pub(crate) fn add_scancode(scancode: u8) {
+    if let Ok(queue) = SCANCODE_QUEUE.try_get() {
+        if let Err(_) = queue.push(scancode) {
+            println!("Keyboard scancode queue full, dropping input {}", scancode);
+        }
+        else {
+            WAKER.wake();
+        }
+    }
+    else {
+        println!("Keyboard scancode queue uninitialized");
+    }
+}
+
+pub async fn print_keypresses() {
+    let mut scancodes = ScancodeStream::new();
+    let mut keyboard: Keyboard<layouts::Us104Key, ScancodeSet1> = 
+        Keyboard::new(layouts::Us104Key, ScancodeSet1, HandleControl::Ignore);
+
+    while let Some(scancode) = scancodes.next().await {
+        if let Ok(Some(key_event)) = keyboard.add_byte(scancode) {
+            if let Some(key) = keyboard.process_keyevent(key_event) {
+                match key {
+                    DecodedKey::Unicode(character) => print!("{}", character),
+                    DecodedKey::RawKey(key) => print!("{:?}", key),
+                }
+            }
+        }
+    }
+}

src/task/mod.rs

@@ -0,0 +1,36 @@
+use core::future::Future;
+use core::pin::Pin;
+use core::sync::atomic::{AtomicU64, Ordering};
+use core::task::{Context, Poll};
+use alloc::boxed::Box;
+
+pub mod executor;
+pub mod keyboard;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+struct TaskId(u64);
+
+impl TaskId {
+    fn new() -> Self {
+        static NEXT_ID: AtomicU64 = AtomicU64::new(0);
+        TaskId(NEXT_ID.fetch_add(1, Ordering::Relaxed))
+    }
+}
+
+pub struct Task {
+    id: TaskId,
+    future: Pin<Box<dyn Future<Output = ()>>>
+}
+
+impl Task {
+    pub fn new(future: impl Future<Output = ()> + 'static) -> Task {
+        Task {
+            id: TaskId::new(),
+            future: Box::pin(future)
+        }
+    }
+
+    fn poll(&mut self, context: &mut Context) -> Poll<()> {
+        self.future.as_mut().poll(context)
+    }
+}