Switch back to official nightly

The Wake trait is based on Arc, which leads to deallocation on wakes. Since interrupts should not (de)allocate, this can lead to a deadlock.

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 +23,10 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
+ "conquer-once",
+ "cooked-waker",
+ "crossbeam-queue",
+ "futures-util",
  "lazy_static",
  "linked_list_allocator",
  "pc-keyboard",
@@ -29,9 +39,51 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.8.8"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3ed4f735c4e455ba86a3d2939b1c0729414153642106c9d035693355630a42c"
+checksum = "152a28c753e229e037e910b4cd4cd16a90c53dd9a67fd751fa304b4b4a03970c"
+
+[[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 = "cooked-waker"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0032e8be0680b63daf14b0fd7fd57f85fd6897951e110b041d32e839a831914"
+dependencies = [
+ "cooked-waker-derive",
+ "stowaway",
+]
+
+[[package]]
+name = "cooked-waker-derive"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "74ded02b04a8ff53ea7328cd71297cde598bee70d165ad92512bdb7e20be9d74"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
 
 [[package]]
 name = "cpuio"
@@ -39,6 +91,49 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "22b8e308ccfc5acf3b82f79c0eac444cf6114cb2ac67a230ca6c177210068daa"
 
+[[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 +176,30 @@ 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 = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c09721c6781493a2a492a96b5a5bf19b65917fe6728884e7c44dd0c60ca3435"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2bdc6c187c65bca4260c9011c9e3132efe4909da44726bad24cf7572ae338d7f"
+dependencies = [
+ "proc-macro2",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.1.0"
@@ -102,6 +221,23 @@ dependencies = [
  "lock_api",
 ]
 
+[[package]]
+name = "stowaway"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32b13d61e782863c0eaeeaf7e8e580dc956a625851fd2fb73e5e92db9601c891"
+
+[[package]]
+name = "syn"
+version = "1.0.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0df0eb663f387145cab623dea85b09c2c5b4b0aef44e945d928e682fce71bb03"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
 [[package]]
 name = "uart_16550"
 version = "0.2.4"
@@ -112,6 +248,12 @@ dependencies = [
  "x86_64",
 ]
 
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
+
 [[package]]
 name = "volatile"
 version = "0.2.6"

Cargo.toml

@@ -13,7 +13,7 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = { version = "0.8.0", features = ["map_physical_memory"]}
+bootloader = { version = "0.8.8", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.9.6"
@@ -21,11 +21,25 @@ uart_16550 = "0.2.0"
 pic8259_simple = "0.1.1"
 pc-keyboard = "0.5.0"
 linked_list_allocator = "0.8.0"
+cooked-waker = "1.0.2"
 
 [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"]
 
 [package.metadata.bootimage]
 test-args = [

src/interrupts.rs

@@ -80,28 +80,11 @@ 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

@@ -18,6 +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

@@ -6,7 +6,6 @@
 
 extern crate alloc;
 
-use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
 use blog_os::println;
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
@@ -16,6 +15,7 @@ entry_point!(kernel_main);
 fn kernel_main(boot_info: &'static BootInfo) -> ! {
     use blog_os::allocator;
     use blog_os::memory::{self, BootInfoFrameAllocator};
+    use blog_os::task::{keyboard, simple_executor::SimpleExecutor, Task};
     use x86_64::VirtAddr;
 
     println!("Hello World{}", "!");
@@ -27,29 +27,10 @@ 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)
-    );
+    let mut executor = SimpleExecutor::new();
+    executor.spawn(Task::new(example_task()));
+    executor.spawn(Task::new(keyboard::print_keypresses()));
+    executor.run();
 
     #[cfg(test)]
     test_main();
@@ -58,6 +39,15 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     blog_os::hlt_loop();
 }
 
+async fn async_number() -> u32 {
+    42
+}
+
+async fn example_task() {
+    let number = async_number().await;
+    println!("async number: {}", number);
+}
+
 /// This function is called on panic.
 #[cfg(not(test))]
 #[panic_handler]

src/task/keyboard.rs

@@ -0,0 +1,79 @@
+use crate::print;
+use crate::println;
+use conquer_once::spin::OnceCell;
+use core::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use crossbeam_queue::ArrayQueue;
+use futures_util::stream::StreamExt;
+use futures_util::{stream::Stream, 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) => 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 +1,26 @@
+use alloc::boxed::Box;
+use core::task::{Context, Poll};
+use core::{future::Future, pin::Pin};
+
+pub mod keyboard;
+pub mod simple_executor;
+
+pub struct Task {
+    future: Pin<Box<dyn Future<Output = ()>>>,
+}
+
+impl Task {
+    pub fn new(future: impl Future<Output = ()> + 'static) -> Task {
+        Task {
+            future: Box::pin(future),
+        }
+    }
+
+    fn poll(&mut self, context: &mut Context) -> Poll<()> {
+        self.future.as_mut().poll(context)
+    }
+
+    fn id(&self) -> usize {
+        &*self.future as *const _ as *const () as usize
+    }
+}

src/task/simple_executor.rs

@@ -0,0 +1,86 @@
+use super::Task;
+use alloc::{
+    collections::{BTreeMap, VecDeque},
+    sync::Arc,
+};
+use cooked_waker::IntoWaker;
+use core::task::{Context, Poll};
+use crossbeam_queue::ArrayQueue;
+
+pub struct SimpleExecutor {
+    task_queue: VecDeque<Task>,
+    waiting_tasks: BTreeMap<usize, Task>,
+    wake_queue: Arc<ArrayQueue<usize>>,
+}
+
+impl SimpleExecutor {
+    pub fn new() -> SimpleExecutor {
+        SimpleExecutor {
+            task_queue: VecDeque::new(),
+            waiting_tasks: BTreeMap::new(),
+            wake_queue: Arc::new(ArrayQueue::new(100)),
+        }
+    }
+
+    pub fn spawn(&mut self, task: Task) {
+        self.task_queue.push_back(task)
+    }
+
+    pub fn run(&mut self) {
+        loop {
+            self.handle_wakeups();
+            self.run_ready_tasks();
+        }
+    }
+
+    fn handle_wakeups(&mut self) {
+        while let Ok(task_id) = self.wake_queue.pop() {
+            if let Some(task) = self.waiting_tasks.remove(&task_id) {
+                self.task_queue.push_back(task);
+            }
+        }
+    }
+
+    fn run_ready_tasks(&mut self) {
+        while let Some(mut task) = self.task_queue.pop_front() {
+            let waker = TaskWaker {
+                task_id: task.id(),
+                wake_queue: self.wake_queue.clone(),
+            }
+            .into_waker();
+            let mut context = Context::from_waker(&waker);
+            match task.poll(&mut context) {
+                Poll::Ready(()) => {} // task done
+                Poll::Pending => {
+                    if self.waiting_tasks.insert(task.id(), task).is_some() {
+                        panic!("Same task inserted into waiting_tasks twice");
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, IntoWaker)]
+struct TaskWaker {
+    task_id: usize,
+    wake_queue: Arc<ArrayQueue<usize>>,
+}
+
+impl TaskWaker {
+    fn wake_task(&self) {
+        self.wake_queue.push(self.task_id).expect("wake queue full");
+    }
+}
+
+impl cooked_waker::WakeRef for TaskWaker {
+    fn wake_by_ref(&self) {
+        self.wake_task();
+    }
+}
+
+impl cooked_waker::Wake for TaskWaker {
+    fn wake(self) {
+        self.wake_task();
+    }
+}