Refactor: Move interrupt wakers/operations into separate modules

Pin implements Deref too, so by dereferencing only once we get a `&Box` reference. Since Box also implements Future, the type of `future_ref` was still correct. To avoid this error in the future, we added an assertion to catch duplicate task IDson `pending_tasks.insert()`.

Cargo.lock

@@ -24,7 +24,6 @@ version = "0.1.0"
 dependencies = [
  "bootloader",
  "conquer-once",
- "cooked-waker",
  "crossbeam-queue",
  "futures-util",
  "lazy_static",
@@ -39,9 +38,9 @@ dependencies = [
 
 [[package]]
 name = "bootloader"
-version = "0.8.9"
+version = "0.8.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "152a28c753e229e037e910b4cd4cd16a90c53dd9a67fd751fa304b4b4a03970c"
+checksum = "c3ed4f735c4e455ba86a3d2939b1c0729414153642106c9d035693355630a42c"
 
 [[package]]
 name = "cfg-if"
@@ -64,27 +63,6 @@ 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"
 version = "0.2.0"
@@ -182,24 +160,6 @@ 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"
@@ -221,23 +181,6 @@ 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"
@@ -248,12 +191,6 @@ 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 = "0.8.8", features = ["map_physical_memory"]}
+bootloader = { version = "0.8.0", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
 x86_64 = "0.9.6"
@@ -21,7 +21,6 @@ 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"
@@ -32,14 +31,14 @@ 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"]
+features = ["alloc", "async-await"]
+
+[dependencies.conquer-once]
+version = "0.2.0"
+default-features = false
 
 [package.metadata.bootimage]
 test-args = [

src/driver/keyboard.rs

@@ -0,0 +1,75 @@
+use crate::{print, println, task::interrupt_wake};
+use conquer_once::spin::OnceCell;
+use core::future::Future;
+use core::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use crossbeam_queue::ArrayQueue;
+use futures_util::task::AtomicWaker;
+use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
+
+static WAKER: AtomicWaker = AtomicWaker::new();
+static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
+
+pub fn init() {
+    SCANCODE_QUEUE
+        .try_init_once(|| ArrayQueue::new(10))
+        .expect("failed to init scancode queue");
+}
+
+/// Called by the keyboard interrupt handler
+///
+/// Must not block (including spinlocks).
+pub(crate) fn keyboard_scancode(scancode: u8) {
+    let scancode_queue = SCANCODE_QUEUE
+        .try_get()
+        .expect("scancode queue not initialized");
+    if let Err(_) = scancode_queue.push(scancode) {
+        println!("WARNING: dropping keyboard input");
+    }
+    if let Some(waker) = WAKER.take() {
+        interrupt_wake(waker);
+    }
+}
+
+fn next_scancode() -> impl Future<Output = u8> {
+    NextScancode
+}
+
+struct NextScancode;
+
+impl Future for NextScancode {
+    type Output = u8;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<u8> {
+        let scancodes = SCANCODE_QUEUE
+            .try_get()
+            .expect("scancode queue not initialized");
+        // fast path
+        if let Ok(scancode) = scancodes.pop() {
+            return Poll::Ready(scancode);
+        }
+
+        WAKER.register(&cx.waker());
+        match scancodes.pop() {
+            Ok(scancode) => Poll::Ready(scancode),
+            Err(crossbeam_queue::PopError) => Poll::Pending,
+        }
+    }
+}
+
+pub async fn keyboard_task() {
+    let mut keyboard = Keyboard::new(layouts::Us104Key, ScancodeSet1, HandleControl::Ignore);
+
+    loop {
+        if let Ok(Some(key_event)) = keyboard.add_byte(next_scancode().await) {
+            if let Some(key) = keyboard.process_keyevent(key_event) {
+                match key {
+                    DecodedKey::Unicode(character) => print!("{}", character),
+                    DecodedKey::RawKey(key) => print!("{:?}", key),
+                }
+            }
+        }
+    }
+}

src/driver/mod.rs

@@ -0,0 +1,6 @@
+pub mod keyboard;
+pub mod timer;
+
+pub fn init() {
+    keyboard::init();
+}

src/driver/timer.rs

@@ -0,0 +1,55 @@
+use crate::{print, task::interrupt_wake};
+use core::future::Future;
+use core::{
+    pin::Pin,
+    sync::atomic::{AtomicU64, Ordering},
+    task::{Context, Poll},
+};
+use futures_util::task::AtomicWaker;
+
+static TICKS: AtomicU64 = AtomicU64::new(0);
+static WAKER: AtomicWaker = AtomicWaker::new();
+
+/// Called by the timer interrupt handler
+///
+/// Must not block (including spinlocks).
+pub(crate) fn tick() {
+    TICKS.fetch_add(1, Ordering::Release);
+    if let Some(waker) = WAKER.take() {
+        interrupt_wake(waker);
+    }
+}
+
+fn next_tick() -> impl Future<Output = u64> {
+    static NEXT_TICK: AtomicU64 = AtomicU64::new(1);
+
+    NextTick {
+        ticks: NEXT_TICK.fetch_add(1, Ordering::Release),
+    }
+}
+
+struct NextTick {
+    ticks: u64,
+}
+
+impl Future for NextTick {
+    type Output = u64;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<u64> {
+        WAKER.register(&cx.waker());
+        let current_ticks = TICKS.load(Ordering::Acquire);
+        if self.ticks < current_ticks {
+            self.ticks += 1;
+            Poll::Ready(self.ticks)
+        } else {
+            Poll::Pending
+        }
+    }
+}
+
+pub async fn timer_task() {
+    loop {
+        next_tick().await;
+        print!(".");
+    }
+}

src/interrupts.rs

@@ -1,4 +1,4 @@
-use crate::{gdt, hlt_loop, print, println};
+use crate::{gdt, hlt_loop, println};
 use lazy_static::lazy_static;
 use pic8259_simple::ChainedPics;
 use spin;
@@ -72,7 +72,8 @@ extern "x86-interrupt" fn double_fault_handler(
 }
 
 extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
-    print!(".");
+    crate::driver::timer::tick();
+
     unsafe {
         PICS.lock()
             .notify_end_of_interrupt(InterruptIndex::Timer.as_u8());
@@ -81,10 +82,10 @@ extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptSt
 
 extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
     use x86_64::instructions::port::Port;
-
     let mut port = Port::new(0x60);
     let scancode: u8 = unsafe { port.read() };
-    crate::task::keyboard::add_scancode(scancode);
+
+    crate::driver::keyboard::keyboard_scancode(scancode);
 
     unsafe {
         PICS.lock()

src/lib.rs

@@ -5,7 +5,10 @@
 #![feature(alloc_error_handler)]
 #![feature(const_fn)]
 #![feature(alloc_layout_extra)]
+#![feature(wake_trait)]
 #![feature(const_in_array_repeat_expressions)]
+#![feature(type_alias_impl_trait)]
+#![feature(asm)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
@@ -14,6 +17,7 @@ extern crate alloc;
 use core::panic::PanicInfo;
 
 pub mod allocator;
+pub mod driver;
 pub mod gdt;
 pub mod interrupts;
 pub mod memory;
@@ -25,7 +29,11 @@ pub fn init() {
     gdt::init();
     interrupts::init_idt();
     unsafe { interrupts::PICS.lock().initialize() };
-    x86_64::instructions::interrupts::enable();
+}
+
+pub fn init_heap_structures() {
+    task::init();
+    driver::init();
 }
 
 pub fn test_runner(tests: &[&dyn Fn()]) {

src/main.rs

@@ -6,6 +6,7 @@
 
 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;
@@ -15,7 +16,6 @@ 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{}", "!");
@@ -26,26 +26,50 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
     let mut frame_allocator = unsafe { BootInfoFrameAllocator::init(&boot_info.memory_map) };
 
     allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
+    blog_os::init_heap_structures();
+
+    // 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)
+    );
+
+    use blog_os::task::executor::Executor;
+
+    let mut executor = Executor::new();
+    executor.spawn(bar());
+
+    executor.spawn(async {
+        #[cfg(test)]
+        test_main();
+    });
+
+    executor.spawn(async {
+        println!("It did not crash!");
+    });
+
+    executor.spawn(blog_os::driver::timer::timer_task());
+    executor.spawn(blog_os::driver::keyboard::keyboard_task());
 
-    let mut executor = SimpleExecutor::new();
-    executor.spawn(Task::new(example_task()));
-    executor.spawn(Task::new(keyboard::print_keypresses()));
     executor.run();
-
-    #[cfg(test)]
-    test_main();
-
-    println!("It did not crash!");
-    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.
@@ -61,3 +85,15 @@ fn panic(info: &PanicInfo) -> ! {
 fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)
 }
+
+async fn test() -> u32 {
+    42
+}
+
+async fn foo() -> u32 {
+    test().await * 2
+}
+
+async fn bar() {
+    println!("foo result: {}", foo().await);
+}

src/task/executor.rs

@@ -0,0 +1,127 @@
+use super::interrupt_wakeups::interrupt_wakeups;
+use crate::println;
+use alloc::{
+    boxed::Box,
+    collections::{BTreeMap, VecDeque},
+    sync::Arc,
+    task::Wake,
+};
+use core::{
+    future::Future,
+    pin::Pin,
+    task::{Context, Poll},
+};
+use crossbeam_queue::SegQueue;
+
+pub type Task = Pin<Box<dyn Future<Output = ()>>>;
+type TaskId = usize;
+
+pub struct Executor {
+    task_queue: VecDeque<Task>,
+    wake_queue: Arc<SegQueue<TaskId>>,
+    pending_tasks: BTreeMap<TaskId, Task>,
+}
+
+impl Executor {
+    pub fn new() -> Self {
+        Executor {
+            task_queue: VecDeque::new(),
+            wake_queue: Arc::new(SegQueue::new()),
+            pending_tasks: BTreeMap::new(),
+        }
+    }
+
+    pub fn spawn(&mut self, task: impl Future<Output = ()> + 'static) {
+        self.task_queue.push_back(Box::pin(task))
+    }
+
+    pub fn run(&mut self) -> ! {
+        loop {
+            self.run_ready_tasks();
+            self.apply_interrupt_wakeups();
+            self.wake_waiting_tasks();
+            self.hlt_if_idle();
+        }
+    }
+
+    fn run_ready_tasks(&mut self) {
+        while let Some(mut task) = self.task_queue.pop_front() {
+            let waker = self.create_waker(&task).into();
+            let mut context = Context::from_waker(&waker);
+            match task.as_mut().poll(&mut context) {
+                Poll::Ready(()) => {} // task done
+                Poll::Pending => {
+                    // add task to pending_tasks and wait for wakeup
+                    let task_id = Self::task_id(&task);
+                    if self.pending_tasks.insert(task_id, task).is_some() {
+                        panic!("Task with same ID already in pending_tasks");
+                    }
+                }
+            }
+        }
+    }
+
+    /// Invoke wakers for tasks woken by interrupts
+    ///
+    /// The interrupt handlers can't invoke the waker directly since wakers
+    /// might execute arbitrary code, e.g. allocate, which should not be done
+    /// in interrupt handlers to avoid deadlocks.
+    fn apply_interrupt_wakeups(&mut self) {
+        while let Ok(waker) = interrupt_wakeups().pop() {
+            waker.wake();
+        }
+    }
+
+    fn wake_waiting_tasks(&mut self) {
+        while let Ok(task_id) = self.wake_queue.pop() {
+            if let Some(task) = self.pending_tasks.remove(&task_id) {
+                self.task_queue.push_back(task);
+            } else {
+                println!("WARNING: woken task not found in pending_tasks");
+            }
+        }
+    }
+
+    /// Executes the `hlt` instruction if there are no ready tasks
+    fn hlt_if_idle(&self) {
+        if self.task_queue.is_empty() {
+            // disable interrupts to avoid races
+            x86_64::instructions::interrupts::disable();
+            // check if relevant interrupts occured since the last check
+            if interrupt_wakeups().is_empty() {
+                // no interrupts occured -> hlt to wait for next interrupt
+                x86_64::instructions::interrupts::enable_interrupts_and_hlt();
+            } else {
+                // there were some new wakeups -> continue execution
+                x86_64::instructions::interrupts::enable();
+            }
+        }
+    }
+
+    fn task_id(task: &Task) -> TaskId {
+        let future_ref: &dyn Future<Output = ()> = &**task;
+        future_ref as *const _ as *const () as usize
+    }
+
+    fn create_waker(&self, task: &Task) -> Arc<Waker> {
+        Arc::new(Waker {
+            wake_queue: self.wake_queue.clone(),
+            task_id: Self::task_id(task),
+        })
+    }
+}
+
+pub struct Waker {
+    wake_queue: Arc<SegQueue<TaskId>>,
+    task_id: TaskId,
+}
+
+impl Wake for Waker {
+    fn wake(self: Arc<Self>) {
+        self.wake_by_ref();
+    }
+
+    fn wake_by_ref(self: &Arc<Self>) {
+        self.wake_queue.push(self.task_id);
+    }
+}

src/task/interrupt_wakeups.rs

@@ -0,0 +1,25 @@
+use crate::println;
+use conquer_once::spin::OnceCell;
+use core::task::Waker;
+use crossbeam_queue::ArrayQueue;
+
+static INTERRUPT_WAKEUPS: OnceCell<ArrayQueue<Waker>> = OnceCell::uninit();
+
+pub fn init() {
+    INTERRUPT_WAKEUPS
+        .try_init_once(|| ArrayQueue::new(10))
+        .expect("failed to init interrupt wakeup queue");
+}
+
+/// Queues a waker for waking in an interrupt-safe way
+pub(crate) fn interrupt_wake(waker: Waker) {
+    if let Err(_) = interrupt_wakeups().push(waker) {
+        println!("WARNING: dropping interrupt wakeup");
+    }
+}
+
+pub(super) fn interrupt_wakeups() -> &'static ArrayQueue<Waker> {
+    INTERRUPT_WAKEUPS
+        .try_get()
+        .expect("interrupt wakeup queue not initialized")
+}

src/task/keyboard.rs

@@ -1,79 +0,0 @@
-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

@@ -1,26 +1,8 @@
-use alloc::boxed::Box;
-use core::task::{Context, Poll};
-use core::{future::Future, pin::Pin};
+pub(crate) use interrupt_wakeups::interrupt_wake;
 
-pub mod keyboard;
-pub mod simple_executor;
+pub mod executor;
+mod interrupt_wakeups;
 
-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
-    }
+pub fn init() {
+    interrupt_wakeups::init();
 }

src/task/simple_executor.rs

@@ -1,86 +0,0 @@
-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();
-    }
-}