Update to latest version

Simplify executor by merging task_queue and wake_queue

Cargo.lock

@@ -1,5 +1,11 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+[[package]]
+name = "autocfg"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"
+
 [[package]]
 name = "bit_field"
 version = "0.9.0"
@@ -17,6 +23,9 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
+ "conquer-once",
+ "crossbeam-queue",
+ "futures-util",
  "lazy_static",
  "linked_list_allocator",
  "pc-keyboard",
@@ -24,7 +33,7 @@ dependencies = [
  "spin",
  "uart_16550",
  "volatile",
- "x86_64",
+ "x86_64 0.11.1",
 ]
 
 [[package]]
@@ -33,12 +42,76 @@ version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "44ac0bdf4930c3c4d7f0d04eb6f15d7dcb9d5972b1ff9cd2bee0128112260fc7"
 
+[[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 = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f7644600a548ecad74e4a918392af1798f7dd045be610be3203b9e129b4f98f"
+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 = "cpuio"
 version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d531514efb06912141fa65967447de805691b685a7565c87d1765afe34a98aa7"
 
+[[package]]
+name = "crossbeam-queue"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c695eeca1e7173472a32221542ae469b3e9aac3a4fc81f7696bcad82029493db"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[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 = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f25592f769825e89b92358db00d26f965761e094951ac44d3663ef25b7ac464a"
+
+[[package]]
+name = "futures-task"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b0a34e53cf6cdcd0178aa573aed466b646eb3db769570841fda0c7ede375a27"
+
+[[package]]
+name = "futures-util"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22766cf25d64306bedf0384da004d05c9974ab104fcc4528f1236181c18004c5"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "pin-utils",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
@@ -81,6 +154,30 @@ dependencies = [
  "cpuio",
 ]
 
+[[package]]
+name = "pin-utils"
+version = "0.1.0-alpha.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "beae6331a816b1f65d04c45b078fd8e6c93e8071771f41b8163255bbd8d7c8fa"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.1.0"
@@ -102,6 +199,17 @@ dependencies = [
  "lock_api",
 ]
 
+[[package]]
+name = "syn"
+version = "1.0.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e8d5d96e8cbb005d6959f119f773bfaebb5684296108fb32600c00cde305b2cd"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
 [[package]]
 name = "uart_16550"
 version = "0.2.7"
@@ -109,9 +217,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e58fc40dc1712664fc9b0a7bd8ca2f21ab49960924fb245a80a05e1e92f3dfe9"
 dependencies = [
  "bitflags",
- "x86_64",
+ "x86_64 0.11.0",
 ]
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
+
 [[package]]
 name = "volatile"
 version = "0.2.6"
@@ -127,3 +241,21 @@ dependencies = [
  "bit_field",
  "bitflags",
 ]
+
+[[package]]
+name = "x86_64"
+version = "0.11.1"
+dependencies = [
+ "bit_field",
+ "bitflags",
+ "x86_64-idt-general-handler",
+]
+
+[[package]]
+name = "x86_64-idt-general-handler"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]

Cargo.toml

@@ -16,7 +16,7 @@ harness = false
 bootloader = { version = "0.9.3", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = "0.11.0"
+x86_64 = { path = "../../x86_64" }
 uart_16550 = "0.2.0"
 pic8259_simple = "0.2.0"
 pc-keyboard = "0.5.0"
@@ -26,6 +26,19 @@ linked_list_allocator = "0.8.0"
 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"]
 
 [package.metadata.bootimage]
 test-args = [

README.md

@@ -1,10 +1,10 @@
-# Blog OS (Allocator Designs)
+# Blog OS (Async/Await)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-11)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-11)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Build%20Code/badge.svg?branch=post-12)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Build+Code%22+branch%3Apost-12)
 
-This repository contains the source code for the [Allocator Designs][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [Async/Await][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/allocator-designs/
+[post]: https://os.phil-opp.com/async-await/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 

src/interrupts.rs

@@ -2,7 +2,9 @@ use crate::{gdt, hlt_loop, print, println};
 use lazy_static::lazy_static;
 use pic8259_simple::ChainedPics;
 use spin;
-use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
+use x86_64::structures::idt::{
+    self, InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode,
+};
 
 pub const PIC_1_OFFSET: u8 = 32;
 pub const PIC_2_OFFSET: u8 = PIC_1_OFFSET + 8;
@@ -30,6 +32,8 @@ pub static PICS: spin::Mutex<ChainedPics> =
 lazy_static! {
     static ref IDT: InterruptDescriptorTable = {
         let mut idt = InterruptDescriptorTable::new();
+
+        idt::set_general_handler!(&mut idt, default_handler);
         idt.breakpoint.set_handler_fn(breakpoint_handler);
         idt.page_fault.set_handler_fn(page_fault_handler);
         unsafe {
@@ -37,8 +41,6 @@ lazy_static! {
                 .set_handler_fn(double_fault_handler)
                 .set_stack_index(gdt::DOUBLE_FAULT_IST_INDEX);
         }
-        idt[InterruptIndex::Timer.as_usize()].set_handler_fn(timer_interrupt_handler);
-        idt[InterruptIndex::Keyboard.as_usize()].set_handler_fn(keyboard_interrupt_handler);
         idt
     };
 }
@@ -47,6 +49,18 @@ pub fn init_idt() {
     IDT.load();
 }
 
+fn default_handler(stack_frame: &mut InterruptStackFrame, index: u8, error_code: Option<u64>) {
+    if index == 32 {
+        print!("{} ", index);
+    } else {
+        println!("INTERRUPT {}: \n{:#?}", index, stack_frame);
+    }
+
+    unsafe {
+        PICS.lock().notify_end_of_interrupt(index);
+    }
+}
+
 extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut InterruptStackFrame) {
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
@@ -80,28 +94,11 @@ extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptSt
 }
 
 extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
-    use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
-    use spin::Mutex;
     use x86_64::instructions::port::Port;
 
-    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(0x60);
-
     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()

src/lib.rs

@@ -5,6 +5,7 @@
 #![feature(alloc_error_handler)]
 #![feature(const_fn)]
 #![feature(const_in_array_repeat_expressions)]
+#![feature(wake_trait)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
@@ -17,6 +18,7 @@ pub mod gdt;
 pub mod interrupts;
 pub mod memory;
 pub mod serial;
+pub mod task;
 pub mod vga_buffer;
 
 pub fn init() {

src/main.rs

@@ -6,8 +6,8 @@
 
 extern crate alloc;
 
-use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
 use blog_os::println;
+use blog_os::task::{executor::Executor, keyboard, Task};
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
@@ -27,35 +27,13 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
 
     allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
 
-    // allocate a number on the heap
-    let heap_value = Box::new(41);
-    println!("heap_value at {:p}", heap_value);
-
-    // create a dynamically sized vector
-    let mut vec = Vec::new();
-    for i in 0..500 {
-        vec.push(i);
-    }
-    println!("vec at {:p}", vec.as_slice());
-
-    // create a reference counted vector -> will be freed when count reaches 0
-    let reference_counted = Rc::new(vec![1, 2, 3]);
-    let cloned_reference = reference_counted.clone();
-    println!(
-        "current reference count is {}",
-        Rc::strong_count(&cloned_reference)
-    );
-    core::mem::drop(reference_counted);
-    println!(
-        "reference count is {} now",
-        Rc::strong_count(&cloned_reference)
-    );
-
     #[cfg(test)]
     test_main();
 
-    println!("It did not crash!");
-    blog_os::hlt_loop();
+    let mut executor = Executor::new();
+    executor.spawn(Task::new(example_task()));
+    executor.spawn(Task::new(keyboard::print_keypresses()));
+    executor.run();
 }
 
 /// This function is called on panic.
@@ -72,6 +50,15 @@ fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)
 }
 
+async fn async_number() -> u32 {
+    42
+}
+
+async fn example_task() {
+    let number = async_number().await;
+    println!("async number: {}", number);
+}
+
 #[test_case]
 fn trivial_assertion() {
     assert_eq!(1, 1);

src/task/executor.rs

@@ -0,0 +1,102 @@
+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 spawn(&mut self, task: Task) {
+        let task_id = task.id;
+        if self.tasks.insert(task.id, task).is_some() {
+            panic!("task with same ID already in tasks");
+        }
+        self.task_queue.push(task_id).expect("queue full");
+    }
+
+    pub fn run(&mut self) -> ! {
+        loop {
+            self.run_ready_tasks();
+            self.sleep_if_idle();
+        }
+    }
+
+    fn run_ready_tasks(&mut self) {
+        // destructure `self` to avoid borrow checker errors
+        let Self {
+            tasks,
+            task_queue,
+            waker_cache,
+        } = self;
+
+        while let Ok(task_id) = task_queue.pop() {
+            let task = match tasks.get_mut(&task_id) {
+                Some(task) => task,
+                None => continue, // task no longer exists
+            };
+            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 done -> remove it and its cached waker
+                    tasks.remove(&task_id);
+                    waker_cache.remove(&task_id);
+                }
+                Poll::Pending => {}
+            }
+        }
+    }
+
+    fn sleep_if_idle(&self) {
+        use x86_64::instructions::interrupts::{self, enable_interrupts_and_hlt};
+
+        interrupts::disable();
+        if self.task_queue.is_empty() {
+            enable_interrupts_and_hlt();
+        } else {
+            interrupts::enable();
+        }
+    }
+}
+
+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 +1,83 @@
+use crate::{print, println};
+use conquer_once::spin::OnceCell;
+use core::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use crossbeam_queue::ArrayQueue;
+use futures_util::{
+    stream::{Stream, StreamExt},
+    task::AtomicWaker,
+};
+use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
+
+static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
+static WAKER: AtomicWaker = AtomicWaker::new();
+
+/// Called by the keyboard interrupt handler
+///
+/// Must not block or allocate.
+pub(crate) fn add_scancode(scancode: u8) {
+    if let Ok(queue) = SCANCODE_QUEUE.try_get() {
+        if let Err(_) = queue.push(scancode) {
+            println!("WARNING: scancode queue full; dropping keyboard input");
+        } else {
+            WAKER.wake();
+        }
+    } else {
+        println!("WARNING: scancode queue uninitialized");
+    }
+}
+
+pub struct ScancodeStream {
+    _private: (),
+}
+
+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("scancode queue not initialized");
+
+        // fast path
+        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 async fn print_keypresses() {
+    let mut scancodes = ScancodeStream::new();
+    let mut keyboard = 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 +1,39 @@
+use alloc::boxed::Box;
+use core::{
+    future::Future,
+    pin::Pin,
+    sync::atomic::{AtomicU64, Ordering},
+    task::{Context, Poll},
+};
+
+pub mod executor;
+pub mod keyboard;
+pub mod simple_executor;
+
+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)
+    }
+}
+
+#[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))
+    }
+}

src/task/simple_executor.rs

@@ -0,0 +1,44 @@
+use super::Task;
+use alloc::collections::VecDeque;
+use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+
+pub struct SimpleExecutor {
+    task_queue: VecDeque<Task>,
+}
+
+impl SimpleExecutor {
+    pub fn new() -> SimpleExecutor {
+        SimpleExecutor {
+            task_queue: VecDeque::new(),
+        }
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        self.task_queue.push_back(task)
+    }
+
+    pub fn run(&mut self) {
+        while let Some(mut task) = self.task_queue.pop_front() {
+            let waker = dummy_waker();
+            let mut context = Context::from_waker(&waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {} // task done
+                Poll::Pending => self.task_queue.push_back(task),
+            }
+        }
+    }
+}
+
+fn dummy_raw_waker() -> RawWaker {
+    fn no_op(_: *const ()) {}
+    fn clone(_: *const ()) -> RawWaker {
+        dummy_raw_waker()
+    }
+
+    let vtable = &RawWakerVTable::new(clone, no_op, no_op, no_op);
+    RawWaker::new(0 as *const (), vtable)
+}
+
+fn dummy_waker() -> Waker {
+    unsafe { Waker::from_raw(dummy_raw_waker()) }
+}