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

@@ -24,6 +24,7 @@ version = "0.1.0"
 dependencies = [
  "bootloader",
  "conquer-once",
+ "cooked-waker",
  "crossbeam-queue",
  "futures-util",
  "lazy_static",
@@ -33,14 +34,14 @@ dependencies = [
  "spin",
  "uart_16550",
  "volatile",
- "x86_64 0.11.1",
+ "x86_64",
 ]
 
 [[package]]
 name = "bootloader"
-version = "0.9.3"
+version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "44ac0bdf4930c3c4d7f0d04eb6f15d7dcb9d5972b1ff9cd2bee0128112260fc7"
+checksum = "152a28c753e229e037e910b4cd4cd16a90c53dd9a67fd751fa304b4b4a03970c"
 
 [[package]]
 name = "cfg-if"
@@ -64,10 +65,31 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
 
 [[package]]
-name = "cpuio"
+name = "cooked-waker"
-version = "0.3.0"
+version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d531514efb06912141fa65967447de805691b685a7565c87d1765afe34a98aa7"
+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"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22b8e308ccfc5acf3b82f79c0eac444cf6114cb2ac67a230ca6c177210068daa"
 
 [[package]]
 name = "crossbeam-queue"
@@ -147,9 +169,9 @@ checksum = "c48392db76c4e9a69e0b3be356c5f97ebb7b14413c5e4fd0af4755dbf86e2fce"
 
 [[package]]
 name = "pic8259_simple"
-version = "0.2.0"
+version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af2a5497fb8e59bf8015f67b7dff238d75ef445e03f23edac24ac3a8f09be952"
+checksum = "dc64b2fd10828da8521b6cdabe0679385d7d2a3a6d4c336b819d1fa31ba35c72"
 dependencies = [
  "cpuio",
 ]
@@ -162,18 +184,18 @@ checksum = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.18"
+version = "1.0.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "beae6331a816b1f65d04c45b078fd8e6c93e8071771f41b8163255bbd8d7c8fa"
+checksum = "6c09721c6781493a2a492a96b5a5bf19b65917fe6728884e7c44dd0c60ca3435"
 dependencies = [
  "unicode-xid",
 ]
 
 [[package]]
 name = "quote"
-version = "1.0.7"
+version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
+checksum = "2bdc6c187c65bca4260c9011c9e3132efe4909da44726bad24cf7572ae338d7f"
 dependencies = [
  "proc-macro2",
 ]
@@ -200,10 +222,16 @@ dependencies = [
 ]
 
 [[package]]
-name = "syn"
+name = "stowaway"
-version = "1.0.33"
+version = "1.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8d5d96e8cbb005d6959f119f773bfaebb5684296108fb32600c00cde305b2cd"
+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",
@@ -212,19 +240,19 @@ dependencies = [
 
 [[package]]
 name = "uart_16550"
-version = "0.2.7"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e58fc40dc1712664fc9b0a7bd8ca2f21ab49960924fb245a80a05e1e92f3dfe9"
+checksum = "d44b0f30cb82b0fbc15b78ade1064226529ad52028bc8cb8accb98ff6f3d7131"
 dependencies = [
  "bitflags",
- "x86_64 0.11.0",
+ "x86_64",
 ]
 
 [[package]]
 name = "unicode-xid"
-version = "0.2.1"
+version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
 
 [[package]]
 name = "volatile"
@@ -234,28 +262,10 @@ checksum = "6af0edf5b4faacc31fc51159244d78d65ec580f021afcef7bd53c04aeabc7f29"
 
 [[package]]
 name = "x86_64"
-version = "0.11.0"
+version = "0.9.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "365de37eb7c6da582cbb510dd0f3f1235d24ff6309a8a96e8a9909cc9bfd608f"
+checksum = "4206b60c9f99766329b66962aa8ddc01df6c7edd02edc046b7a69d5df9fcdbcf"
 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

@@ -13,14 +13,15 @@ name = "stack_overflow"
 harness = false
 
 [dependencies]
-bootloader = { version = "0.9.3", features = ["map_physical_memory"]}
+bootloader = { version = "0.8.8", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = { path = "../../x86_64" }
+x86_64 = "0.9.6"
 uart_16550 = "0.2.0"
-pic8259_simple = "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"

README.md

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

src/allocator.rs

@@ -35,7 +35,7 @@ pub fn init_heap(
             .allocate_frame()
             .ok_or(MapToError::FrameAllocationFailed)?;
         let flags = PageTableFlags::PRESENT | PageTableFlags::WRITABLE;
-        unsafe { mapper.map_to(page, frame, flags, frame_allocator)?.flush() };
+        mapper.map_to(page, frame, flags, frame_allocator)?.flush();
     }
 
     unsafe {

src/allocator/linked_list.rs

@@ -45,7 +45,7 @@ impl LinkedListAllocator {
     /// Adds the given memory region to the front of the list.
     unsafe fn add_free_region(&mut self, addr: usize, size: usize) {
         // ensure that the freed region is capable of holding ListNode
-        assert_eq!(align_up(addr, mem::align_of::<ListNode>()), addr);
+        assert!(align_up(addr, mem::align_of::<ListNode>()) == addr);
         assert!(size >= mem::size_of::<ListNode>());
 
         // create a new list node and append it at the start of the list

src/interrupts.rs

@@ -2,9 +2,7 @@ use crate::{gdt, hlt_loop, print, println};
 use lazy_static::lazy_static;
 use pic8259_simple::ChainedPics;
 use spin;
-use x86_64::structures::idt::{
+use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
-    self, InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode,
-};
 
 pub const PIC_1_OFFSET: u8 = 32;
 pub const PIC_2_OFFSET: u8 = PIC_1_OFFSET + 8;
@@ -32,8 +30,6 @@ 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 {
@@ -41,6 +37,8 @@ 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
     };
 }
@@ -49,18 +47,6 @@ 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);
 }
@@ -106,8 +92,13 @@ extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut Interrup
     }
 }
 
+#[cfg(test)]
+use crate::{serial_print, serial_println};
+
 #[test_case]
 fn test_breakpoint_exception() {
+    serial_print!("test_breakpoint_exception...");
     // invoke a breakpoint exception
     x86_64::instructions::interrupts::int3();
+    serial_println!("[ok]");
 }

src/lib.rs

@@ -4,8 +4,8 @@
 #![feature(abi_x86_interrupt)]
 #![feature(alloc_error_handler)]
 #![feature(const_fn)]
+#![feature(alloc_layout_extra)]
 #![feature(const_in_array_repeat_expressions)]
-#![feature(wake_trait)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
@@ -27,25 +27,11 @@ pub fn init() {
     unsafe { interrupts::PICS.lock().initialize() };
     x86_64::instructions::interrupts::enable();
 }
-pub trait Testable {
-    fn run(&self) -> ();
-}
 
-impl<T> Testable for T
+pub fn test_runner(tests: &[&dyn Fn()]) {
-where
-    T: Fn(),
-{
-    fn run(&self) {
-        serial_print!("{}...\t", core::any::type_name::<T>());
-        self();
-        serial_println!("[ok]");
-    }
-}
-
-pub fn test_runner(tests: &[&dyn Testable]) {
     serial_println!("Running {} tests", tests.len());
     for test in tests {
-        test.run();
+        test();
     }
     exit_qemu(QemuExitCode::Success);
 }

src/main.rs

@@ -7,7 +7,6 @@
 extern crate alloc;
 
 use blog_os::println;
-use blog_os::task::{executor::Executor, keyboard, Task};
 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{}", "!");
@@ -27,13 +27,25 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
 
     allocator::init_heap(&mut mapper, &mut frame_allocator).expect("heap initialization failed");
 
-    #[cfg(test)]
+    let mut executor = SimpleExecutor::new();
-    test_main();
-
-    let mut executor = Executor::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.
@@ -49,17 +61,3 @@ fn panic(info: &PanicInfo) -> ! {
 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/memory.rs

@@ -2,6 +2,7 @@ use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
     structures::paging::{
         FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
+        UnusedPhysFrame,
     },
     PhysAddr, VirtAddr,
 };
@@ -44,12 +45,11 @@ pub fn create_example_mapping(
     use x86_64::structures::paging::PageTableFlags as Flags;
 
     let frame = PhysFrame::containing_address(PhysAddr::new(0xb8000));
+    // FIXME: ONLY FOR TEMPORARY TESTING
+    let unused_frame = unsafe { UnusedPhysFrame::new(frame) };
     let flags = Flags::PRESENT | Flags::WRITABLE;
 
-    let map_to_result = unsafe {
+    let map_to_result = mapper.map_to(page, unused_frame, flags, frame_allocator);
-        // FIXME: this is not safe, we do it only for testing
-        mapper.map_to(page, frame, flags, frame_allocator)
-    };
     map_to_result.expect("map_to failed").flush();
 }
 
@@ -57,7 +57,7 @@ pub fn create_example_mapping(
 pub struct EmptyFrameAllocator;
 
 unsafe impl FrameAllocator<Size4KiB> for EmptyFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
+    fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
         None
     }
 }
@@ -82,7 +82,7 @@ impl BootInfoFrameAllocator {
     }
 
     /// Returns an iterator over the usable frames specified in the memory map.
-    fn usable_frames(&self) -> impl Iterator<Item = PhysFrame> {
+    fn usable_frames(&self) -> impl Iterator<Item = UnusedPhysFrame> {
         // get usable regions from memory map
         let regions = self.memory_map.iter();
         let usable_regions = regions.filter(|r| r.region_type == MemoryRegionType::Usable);
@@ -91,12 +91,14 @@ impl BootInfoFrameAllocator {
         // transform to an iterator of frame start addresses
         let frame_addresses = addr_ranges.flat_map(|r| r.step_by(4096));
         // create `PhysFrame` types from the start addresses
-        frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)))
+        let frames = frame_addresses.map(|addr| PhysFrame::containing_address(PhysAddr::new(addr)));
+        // we know that the frames are really unused
+        frames.map(|f| unsafe { UnusedPhysFrame::new(f) })
     }
 }
 
 unsafe impl FrameAllocator<Size4KiB> for BootInfoFrameAllocator {
-    fn allocate_frame(&mut self) -> Option<PhysFrame> {
+    fn allocate_frame(&mut self) -> Option<UnusedPhysFrame> {
         let frame = self.usable_frames().nth(self.next);
         self.next += 1;
         frame

src/task/executor.rs

@@ -1,102 +0,0 @@
-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

@@ -1,14 +1,13 @@
-use crate::{print, println};
+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::{
+use futures_util::stream::StreamExt;
-    stream::{Stream, StreamExt},
+use futures_util::{stream::Stream, task::AtomicWaker};
-    task::AtomicWaker,
-};
 use pc_keyboard::{layouts, DecodedKey, HandleControl, Keyboard, ScancodeSet1};
 
 static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
@@ -57,10 +56,7 @@ impl Stream for ScancodeStream {
 
         WAKER.register(&cx.waker());
         match queue.pop() {
-            Ok(scancode) => {
+            Ok(scancode) => Poll::Ready(Some(scancode)),
-                WAKER.take();
-                Poll::Ready(Some(scancode))
-            }
             Err(crossbeam_queue::PopError) => Poll::Pending,
         }
     }

src/task/mod.rs

@@ -1,24 +1,17 @@
 use alloc::boxed::Box;
-use core::{
+use core::task::{Context, Poll};
-    future::Future,
+use core::{future::Future, pin::Pin};
-    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),
         }
     }
@@ -26,14 +19,8 @@ impl Task {
     fn poll(&mut self, context: &mut Context) -> Poll<()> {
         self.future.as_mut().poll(context)
     }
-}
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+    fn id(&self) -> usize {
-struct TaskId(u64);
+        &*self.future as *const _ as *const () as usize
-
-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

@@ -1,15 +1,24 @@
 use super::Task;
-use alloc::collections::VecDeque;
+use alloc::{
-use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+    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)),
         }
     }
 
@@ -18,27 +27,60 @@ impl SimpleExecutor {
     }
 
     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 = dummy_waker();
+            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 => self.task_queue.push_back(task),
+                Poll::Pending => {
+                    if self.waiting_tasks.insert(task.id(), task).is_some() {
+                        panic!("Same task inserted into waiting_tasks twice");
+                    }
+                }
             }
         }
     }
 }
 
-fn dummy_raw_waker() -> RawWaker {
+#[derive(Debug, Clone, IntoWaker)]
-    fn no_op(_: *const ()) {}
+struct TaskWaker {
-    fn clone(_: *const ()) -> RawWaker {
+    task_id: usize,
-        dummy_raw_waker()
+    wake_queue: Arc<ArrayQueue<usize>>,
+}
+
+impl TaskWaker {
+    fn wake_task(&self) {
+        self.wake_queue.push(self.task_id).expect("wake queue full");
     }
-
-    let vtable = &RawWakerVTable::new(clone, no_op, no_op, no_op);
-    RawWaker::new(0 as *const (), vtable)
 }
 
-fn dummy_waker() -> Waker {
+impl cooked_waker::WakeRef for TaskWaker {
-    unsafe { Waker::from_raw(dummy_raw_waker()) }
+    fn wake_by_ref(&self) {
+        self.wake_task();
+    }
+}
+
+impl cooked_waker::Wake for TaskWaker {
+    fn wake(self) {
+        self.wake_task();
+    }
 }

src/vga_buffer.rs

@@ -3,6 +3,9 @@ use lazy_static::lazy_static;
 use spin::Mutex;
 use volatile::Volatile;
 
+#[cfg(test)]
+use crate::{serial_print, serial_println};
+
 lazy_static! {
     /// A global `Writer` instance that can be used for printing to the VGA text buffer.
     ///
@@ -177,14 +180,18 @@ pub fn _print(args: fmt::Arguments) {
 
 #[test_case]
 fn test_println_simple() {
+    serial_print!("test_println... ");
     println!("test_println_simple output");
+    serial_println!("[ok]");
 }
 
 #[test_case]
 fn test_println_many() {
+    serial_print!("test_println_many... ");
     for _ in 0..200 {
         println!("test_println_many output");
     }
+    serial_println!("[ok]");
 }
 
 #[test_case]
@@ -192,6 +199,8 @@ fn test_println_output() {
     use core::fmt::Write;
     use x86_64::instructions::interrupts;
 
+    serial_print!("test_println_output... ");
+
     let s = "Some test string that fits on a single line";
     interrupts::without_interrupts(|| {
         let mut writer = WRITER.lock();
@@ -201,4 +210,6 @@ fn test_println_output() {
             assert_eq!(char::from(screen_char.ascii_character), c);
         }
     });
+
+    serial_println!("[ok]");
 }

tests/basic_boot.rs

@@ -4,7 +4,7 @@
 #![test_runner(blog_os::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
-use blog_os::println;
+use blog_os::{println, serial_print, serial_println};
 use core::panic::PanicInfo;
 
 #[no_mangle] // don't mangle the name of this function
@@ -21,5 +21,7 @@ fn panic(info: &PanicInfo) -> ! {
 
 #[test_case]
 fn test_println() {
+    serial_print!("test_println... ");
     println!("test_println output");
+    serial_println!("[ok]");
 }

tests/heap_allocation.rs

@@ -7,7 +7,7 @@
 extern crate alloc;
 
 use alloc::{boxed::Box, vec::Vec};
-use blog_os::allocator::HEAP_SIZE;
+use blog_os::{allocator::HEAP_SIZE, serial_print, serial_println};
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
@@ -30,38 +30,44 @@ fn main(boot_info: &'static BootInfo) -> ! {
 
 #[test_case]
 fn simple_allocation() {
-    let heap_value_1 = Box::new(41);
+    serial_print!("simple_allocation... ");
-    let heap_value_2 = Box::new(13);
+    let heap_value = Box::new(41);
-    assert_eq!(*heap_value_1, 41);
+    assert_eq!(*heap_value, 41);
-    assert_eq!(*heap_value_2, 13);
+    serial_println!("[ok]");
 }
 
 #[test_case]
 fn large_vec() {
+    serial_print!("large_vec... ");
     let n = 1000;
     let mut vec = Vec::new();
     for i in 0..n {
         vec.push(i);
     }
     assert_eq!(vec.iter().sum::<u64>(), (n - 1) * n / 2);
+    serial_println!("[ok]");
 }
 
 #[test_case]
 fn many_boxes() {
+    serial_print!("many_boxes... ");
     for i in 0..HEAP_SIZE {
         let x = Box::new(i);
         assert_eq!(*x, i);
     }
+    serial_println!("[ok]");
 }
 
 #[test_case]
 fn many_boxes_long_lived() {
+    serial_print!("many_boxes_long_lived... ");
     let long_lived = Box::new(1); // new
     for i in 0..HEAP_SIZE {
         let x = Box::new(i);
         assert_eq!(*x, i);
     }
     assert_eq!(*long_lived, 1); // new
+    serial_println!("[ok]");
 }
 
 #[panic_handler]

tests/should_panic.rs

@@ -13,7 +13,7 @@ pub extern "C" fn _start() -> ! {
 }
 
 fn should_fail() {
-    serial_print!("should_panic::should_fail...\t");
+    serial_print!("should_fail... ");
     assert_eq!(0, 1);
 }
 

tests/stack_overflow.rs

@@ -9,7 +9,7 @@ use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame};
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
-    serial_print!("stack_overflow::stack_overflow...\t");
+    serial_print!("stack_overflow... ");
 
     blog_os::gdt::init();
     init_test_idt();
@@ -23,7 +23,6 @@ pub extern "C" fn _start() -> ! {
 #[allow(unconditional_recursion)]
 fn stack_overflow() {
     stack_overflow(); // for each recursion, the return address is pushed
-    volatile::Volatile::new(0).read(); // prevent tail recursion optimizations
 }
 
 lazy_static! {