Refactor: Move interrupt wakers/operations into separate modules

Update linked_list_allocator to v0.8.0

Cargo.lock

@@ -1,13 +1,10 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
 [[package]]
-name = "array-init"
-version = "0.0.4"
+name = "autocfg"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "23589ecb866b460d3a0f1278834750268c607e8e28a1b982c907219f3178cd72"
-dependencies = [
- "nodrop",
-]
+checksum = "f8aac770f1885fd7e387acedd76065302551364496e46b3dd00860b2f8359b9d"
 
 [[package]]
 name = "bit_field"
@@ -26,6 +23,9 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
+ "conquer-once",
+ "crossbeam-queue",
+ "futures-util",
  "lazy_static",
  "linked_list_allocator",
  "pc-keyboard",
@@ -33,30 +33,85 @@ dependencies = [
  "spin",
  "uart_16550",
  "volatile",
- "x86_64 0.8.1",
+ "x86_64",
 ]
 
 [[package]]
 name = "bootloader"
-version = "0.8.3"
+version = "0.8.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d596849a47f28abdea62d7a6a25c4f6e69c3d9b09b0a2877db6e9cda004ca993"
+checksum = "c3ed4f735c4e455ba86a3d2939b1c0729414153642106c9d035693355630a42c"
 
 [[package]]
-name = "cast"
-version = "0.2.3"
+name = "cfg-if"
+version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4b9434b9a5aa1450faa3f9cb14ea0e8c53bb5d2b3c1bfd1ab4fc03e9f33fbfb0"
+checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
+
+[[package]]
+name = "conquer-once"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f7644600a548ecad74e4a918392af1798f7dd045be610be3203b9e129b4f98f"
 dependencies = [
- "rustc_version",
+ "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 = "0.2.0"
 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"
@@ -68,24 +123,27 @@ dependencies = [
 
 [[package]]
 name = "linked_list_allocator"
-version = "0.6.4"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "47314ec1d29aa869ee7cb5a5be57be9b1055c56567d59c3fb6689926743e0bea"
+checksum = "18c618c431dfe4419afbe22852f6aceffbc17bd82ba0a18b982def291000824c"
 dependencies = [
- "spin",
+ "spinning_top",
 ]
 
 [[package]]
-name = "nodrop"
-version = "0.1.14"
+name = "lock_api"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
+checksum = "79b2de95ecb4691949fea4716ca53cdbcfccb2c612e19644a8bad05edcf9f47b"
+dependencies = [
+ "scopeguard",
+]
 
 [[package]]
 name = "pc-keyboard"
-version = "0.3.1"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fff50ab09ba31bcebc0669f4e64c0952fae1acdca9e6e0587e68e4e8443808ac"
+checksum = "c48392db76c4e9a69e0b3be356c5f97ebb7b14413c5e4fd0af4755dbf86e2fce"
 
 [[package]]
 name = "pic8259_simple"
@@ -97,28 +155,16 @@ dependencies = [
 ]
 
 [[package]]
-name = "rustc_version"
-version = "0.2.3"
+name = "pin-utils"
+version = "0.1.0-alpha.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "138e3e0acb6c9fb258b19b67cb8abd63c00679d2851805ea151465464fe9030a"
-dependencies = [
- "semver",
-]
+checksum = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
 
 [[package]]
-name = "semver"
-version = "0.9.0"
+name = "scopeguard"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
-dependencies = [
- "semver-parser",
-]
-
-[[package]]
-name = "semver-parser"
-version = "0.7.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
 [[package]]
 name = "spin"
@@ -127,20 +173,23 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
 [[package]]
-name = "uart_16550"
-version = "0.2.1"
+name = "spinning_top"
+version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "803ea8cb602dbb32c1a657a866d2dd79fe7dbeab0fb2ac667cb4dcc7de12a58b"
+checksum = "32d801a3a53bcf5071f85fef8d5cab9e5f638fc5580a37e6eb7aba4b37438d24"
 dependencies = [
- "bitflags",
- "x86_64 0.7.7",
+ "lock_api",
 ]
 
 [[package]]
-name = "ux"
-version = "0.1.3"
+name = "uart_16550"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "88dfeb711b61ce620c0cb6fd9f8e3e678622f0c971da2a63c4b3e25e88ed012f"
+checksum = "d44b0f30cb82b0fbc15b78ade1064226529ad52028bc8cb8accb98ff6f3d7131"
+dependencies = [
+ "bitflags",
+ "x86_64",
+]
 
 [[package]]
 name = "volatile"
@@ -150,25 +199,10 @@ checksum = "6af0edf5b4faacc31fc51159244d78d65ec580f021afcef7bd53c04aeabc7f29"
 
 [[package]]
 name = "x86_64"
-version = "0.7.7"
+version = "0.9.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1f27d9168654aee1b0c1b73746caeb4aa33248f8b8c8f6e100e697fcc2a794b2"
+checksum = "4206b60c9f99766329b66962aa8ddc01df6c7edd02edc046b7a69d5df9fcdbcf"
 dependencies = [
- "array-init",
  "bit_field",
  "bitflags",
- "cast",
- "ux",
-]
-
-[[package]]
-name = "x86_64"
-version = "0.8.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f21672dcbed52bc09eea030d189600c0189c66c97bc5b31779eb780e064a201f"
-dependencies = [
- "array-init",
- "bit_field",
- "bitflags",
- "cast",
 ]

Cargo.toml

@@ -16,16 +16,29 @@ harness = false
 bootloader = { version = "0.8.0", features = ["map_physical_memory"]}
 volatile = "0.2.6"
 spin = "0.5.2"
-x86_64 = "0.8.1"
+x86_64 = "0.9.6"
 uart_16550 = "0.2.0"
 pic8259_simple = "0.1.1"
-pc-keyboard = "0.3.1"
-linked_list_allocator = "0.6.4"
+pc-keyboard = "0.5.0"
+linked_list_allocator = "0.8.0"
 
 [dependencies.lazy_static]
 version = "1.0"
 features = ["spin_no_std"]
 
+[dependencies.crossbeam-queue]
+version = "0.2.1"
+default-features = false
+features = ["alloc"]
+
+[dependencies.futures-util]
+version = "0.3.4"
+default-features = false
+features = ["alloc", "async-await"]
+
+[dependencies.conquer-once]
+version = "0.2.0"
+default-features = false
 
 [package.metadata.bootimage]
 test-args = [
@@ -33,6 +46,3 @@ test-args = [
     "-display", "none"
 ]
 test-success-exit-code = 33         # (0x10 << 1) | 1
-
-[profile.release]
-lto = true

src/allocator.rs

@@ -21,7 +21,7 @@ static ALLOCATOR: Locked<FixedSizeBlockAllocator> = Locked::new(FixedSizeBlockAl
 pub fn init_heap(
     mapper: &mut impl Mapper<Size4KiB>,
     frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-) -> Result<(), MapToError> {
+) -> Result<(), MapToError<Size4KiB>> {
     let page_range = {
         let heap_start = VirtAddr::new(HEAP_START as u64);
         let heap_end = heap_start + HEAP_SIZE - 1u64;
@@ -74,11 +74,9 @@ impl<A> Locked<A> {
     }
 }
 
+/// Align the given address `addr` upwards to alignment `align`.
+///
+/// Requires that `align` is a power of two.
 fn align_up(addr: usize, align: usize) -> usize {
-    let remainder = addr % align;
-    if remainder == 0 {
-        addr // addr already aligned
-    } else {
-        addr - remainder + align
-    }
+    (addr + align - 1) & !(align - 1)
 }

src/allocator/bump.rs

@@ -26,7 +26,7 @@ impl BumpAllocator {
     /// memory range is unused. Also, this method must be called only once.
     pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
         self.heap_start = heap_start;
-        self.heap_end = heap_start + heap_size;
+        self.heap_end = heap_start.saturating_add(heap_size);
         self.next = heap_start;
     }
 }
@@ -36,7 +36,10 @@ unsafe impl GlobalAlloc for Locked<BumpAllocator> {
         let mut bump = self.lock(); // get a mutable reference
 
         let alloc_start = align_up(bump.next, layout.align());
-        let alloc_end = alloc_start + layout.size();
+        let alloc_end = match alloc_start.checked_add(layout.size()) {
+            Some(end) => end,
+            None => return ptr::null_mut(),
+        };
 
         if alloc_end > bump.heap_end {
             ptr::null_mut() // out of memory

src/allocator/linked_list.rs

@@ -86,7 +86,7 @@ impl LinkedListAllocator {
     /// Returns the allocation start address on success.
     fn alloc_from_region(region: &ListNode, size: usize, align: usize) -> Result<usize, ()> {
         let alloc_start = align_up(region.start_addr(), align);
-        let alloc_end = alloc_start + size;
+        let alloc_end = alloc_start.checked_add(size).ok_or(())?;
 
         if alloc_end > region.end_addr() {
             // region too small
@@ -122,10 +122,10 @@ unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
         // perform layout adjustments
         let (size, align) = LinkedListAllocator::size_align(layout);
-        let mut allocator = self.inner.lock();
+        let mut allocator = self.lock();
 
         if let Some((region, alloc_start)) = allocator.find_region(size, align) {
-            let alloc_end = alloc_start + size;
+            let alloc_end = alloc_start.checked_add(size).expect("overflow");
             let excess_size = region.end_addr() - alloc_end;
             if excess_size > 0 {
                 allocator.add_free_region(alloc_end, excess_size);
@@ -140,6 +140,6 @@ unsafe impl GlobalAlloc for Locked<LinkedListAllocator> {
         // perform layout adjustments
         let (size, _) = LinkedListAllocator::size_align(layout);
 
-        self.inner.lock().add_free_region(ptr as usize, size)
+        self.lock().add_free_region(ptr as usize, size)
     }
 }

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;
@@ -72,36 +72,20 @@ 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());
     }
-    crate::multitasking::invoke_scheduler();
 }
 
 extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: &mut InterruptStackFrame) {
-    use pc_keyboard::{layouts, DecodedKey, 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));
-    }
-
-    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::driver::keyboard::keyboard_scancode(scancode);
 
     unsafe {
         PICS.lock()

src/lib.rs

@@ -5,13 +5,10 @@
 #![feature(alloc_error_handler)]
 #![feature(const_fn)]
 #![feature(alloc_layout_extra)]
+#![feature(wake_trait)]
 #![feature(const_in_array_repeat_expressions)]
-#![feature(global_asm)]
+#![feature(type_alias_impl_trait)]
 #![feature(asm)]
-#![feature(raw)]
-#![feature(never_type)]
-#![feature(naked_functions)]
-#![feature(option_expect_none)]
 #![test_runner(crate::test_runner)]
 #![reexport_test_harness_main = "test_main"]
 
@@ -20,18 +17,23 @@ extern crate alloc;
 use core::panic::PanicInfo;
 
 pub mod allocator;
+pub mod driver;
 pub mod gdt;
 pub mod interrupts;
 pub mod memory;
-pub mod multitasking;
 pub mod serial;
+pub mod task;
 pub mod vga_buffer;
 
 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

@@ -7,8 +7,7 @@
 extern crate alloc;
 
 use alloc::{boxed::Box, rc::Rc, vec, vec::Vec};
-use blog_os::multitasking::{self, thread::Thread, with_scheduler};
-use blog_os::{print, println};
+use blog_os::println;
 use bootloader::{entry_point, BootInfo};
 use core::panic::PanicInfo;
 
@@ -27,6 +26,7 @@ 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);
@@ -52,48 +52,30 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
         Rc::strong_count(&cloned_reference)
     );
 
-    #[cfg(test)]
-    test_main();
+    use blog_os::task::executor::Executor;
 
-    let idle_thread = Thread::create(idle_thread, 2, &mut mapper, &mut frame_allocator).unwrap();
-    with_scheduler(|s| s.set_idle_thread(idle_thread));
+    let mut executor = Executor::new();
+    executor.spawn(bar());
 
-    for _ in 0..10 {
-        let thread = Thread::create(thread_entry, 2, &mut mapper, &mut frame_allocator).unwrap();
-        with_scheduler(|s| s.add_new_thread(thread));
-    }
-    let thread =
-        Thread::create_from_closure(|| thread_entry(), 2, &mut mapper, &mut frame_allocator)
-            .unwrap();
-    with_scheduler(|s| s.add_new_thread(thread));
+    executor.spawn(async {
+        #[cfg(test)]
+        test_main();
+    });
 
-    println!("It did not crash!");
-    thread_entry();
-}
+    executor.spawn(async {
+        println!("It did not crash!");
+    });
 
-fn idle_thread() -> ! {
-    loop {
-        x86_64::instructions::hlt();
-        multitasking::yield_now();
-    }
-}
+    executor.spawn(blog_os::driver::timer::timer_task());
+    executor.spawn(blog_os::driver::keyboard::keyboard_task());
 
-fn thread_entry() -> ! {
-    let thread_id = with_scheduler(|s| s.current_thread_id()).as_u64();
-    for _ in 0..=thread_id {
-        print!("{}", thread_id);
-        x86_64::instructions::hlt();
-    }
-    multitasking::exit_thread();
+    executor.run();
 }
 
 /// This function is called on panic.
 #[cfg(not(test))]
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
-    unsafe {
-        blog_os::vga_buffer::WRITER.force_unlock();
-    }
     println!("{}", info);
     blog_os::hlt_loop();
 }
@@ -103,3 +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/memory.rs

@@ -1,7 +1,7 @@
 use bootloader::bootinfo::{MemoryMap, MemoryRegionType};
 use x86_64::{
     structures::paging::{
-        mapper, FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
+        FrameAllocator, Mapper, OffsetPageTable, Page, PageTable, PhysFrame, Size4KiB,
         UnusedPhysFrame,
     },
     PhysAddr, VirtAddr,
@@ -36,54 +36,6 @@ unsafe fn active_level_4_table(physical_memory_offset: VirtAddr) -> &'static mut
     &mut *page_table_ptr // unsafe
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub struct StackBounds {
-    start: VirtAddr,
-    end: VirtAddr,
-}
-
-impl StackBounds {
-    pub fn start(&self) -> VirtAddr {
-        self.start
-    }
-
-    pub fn end(&self) -> VirtAddr {
-        self.end
-    }
-}
-
-pub fn alloc_stack(
-    size_in_pages: u64,
-    mapper: &mut impl Mapper<Size4KiB>,
-    frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-) -> Result<StackBounds, mapper::MapToError> {
-    use core::sync::atomic::{AtomicU64, Ordering};
-    use x86_64::structures::paging::PageTableFlags as Flags;
-
-    static STACK_ALLOC_NEXT: AtomicU64 = AtomicU64::new(0x_5555_5555_0000);
-
-    let guard_page_start = STACK_ALLOC_NEXT.fetch_add(
-        (size_in_pages + 1) * Page::<Size4KiB>::SIZE,
-        Ordering::SeqCst,
-    );
-    let guard_page = Page::from_start_address(VirtAddr::new(guard_page_start))
-        .expect("`STACK_ALLOC_NEXT` not page aligned");
-
-    let stack_start = guard_page + 1;
-    let stack_end = stack_start + size_in_pages;
-    let flags = Flags::PRESENT | Flags::WRITABLE;
-    for page in Page::range(stack_start, stack_end) {
-        let frame = frame_allocator
-            .allocate_frame()
-            .ok_or(mapper::MapToError::FrameAllocationFailed)?;
-        mapper.map_to(page, frame, flags, frame_allocator)?.flush();
-    }
-    Ok(StackBounds {
-        start: stack_start.start_address(),
-        end: stack_end.start_address(),
-    })
-}
-
 /// Creates an example mapping for the given page to frame `0xb8000`.
 pub fn create_example_mapping(
     page: Page,

src/multitasking/context_switch.rs

@@ -1,105 +0,0 @@
-use super::{with_scheduler, SwitchReason};
-use crate::multitasking::thread::ThreadId;
-use alloc::boxed::Box;
-use core::mem;
-use core::raw::TraitObject;
-use x86_64::VirtAddr;
-
-pub struct Stack {
-    pointer: VirtAddr,
-}
-
-impl Stack {
-    pub unsafe fn new(stack_pointer: VirtAddr) -> Self {
-        Stack {
-            pointer: stack_pointer,
-        }
-    }
-
-    pub fn get_stack_pointer(self) -> VirtAddr {
-        self.pointer
-    }
-
-    pub fn set_up_for_closure(&mut self, closure: Box<dyn FnOnce() -> !>) {
-        let trait_object: TraitObject = unsafe { mem::transmute(closure) };
-        unsafe { self.push(trait_object.data) };
-        unsafe { self.push(trait_object.vtable) };
-
-        self.set_up_for_entry_point(call_closure_entry);
-    }
-
-    pub fn set_up_for_entry_point(&mut self, entry_point: fn() -> !) {
-        unsafe { self.push(entry_point) };
-        let rflags: u64 = 0x200;
-        unsafe { self.push(rflags) };
-    }
-
-    unsafe fn push<T>(&mut self, value: T) {
-        self.pointer -= core::mem::size_of::<T>();
-        let ptr: *mut T = self.pointer.as_mut_ptr();
-        ptr.write(value);
-    }
-}
-
-pub unsafe fn context_switch_to(
-    new_stack_pointer: VirtAddr,
-    prev_thread_id: ThreadId,
-    switch_reason: SwitchReason,
-) {
-    asm!(
-        "call asm_context_switch"
-        :
-        : "{rdi}"(new_stack_pointer), "{rsi}"(prev_thread_id), "{rdx}"(switch_reason as u64)
-        : "rax", "rbx", "rcx", "rdx", "rsi", "rdi", "rbp", "r8", "r9", "r10",
-        "r11", "r12", "r13", "r14", "r15", "rflags", "memory"
-        : "intel", "volatile"
-    );
-}
-
-global_asm!(
-    "
-    .intel_syntax noprefix
-
-    // asm_context_switch(stack_pointer: u64, thread_id: u64)
-    asm_context_switch:
-        pushfq
-
-        mov rax, rsp
-        mov rsp, rdi
-
-        mov rdi, rax
-        call add_paused_thread
-
-        popfq
-        ret
-"
-);
-
-#[no_mangle]
-pub extern "C" fn add_paused_thread(
-    paused_stack_pointer: VirtAddr,
-    paused_thread_id: ThreadId,
-    switch_reason: SwitchReason,
-) {
-    with_scheduler(|s| s.add_paused_thread(paused_stack_pointer, paused_thread_id, switch_reason));
-}
-
-#[naked]
-fn call_closure_entry() -> ! {
-    unsafe {
-        asm!("
-        pop rsi
-        pop rdi
-        call call_closure
-    " ::: "mem" : "intel", "volatile")
-    };
-    unreachable!();
-}
-
-// no_mangle required because of https://github.com/rust-lang/rust/issues/68136
-#[no_mangle]
-extern "C" fn call_closure(data: *mut (), vtable: *mut ()) -> ! {
-    let trait_object = TraitObject { data, vtable };
-    let f: Box<dyn FnOnce() -> !> = unsafe { mem::transmute(trait_object) };
-    f()
-}

src/multitasking/mod.rs

@@ -1,57 +0,0 @@
-use scheduler::Scheduler;
-
-pub mod context_switch;
-pub mod scheduler;
-pub mod thread;
-
-static SCHEDULER: spin::Mutex<Option<Scheduler>> = spin::Mutex::new(None);
-
-#[repr(u64)]
-pub enum SwitchReason {
-    Paused,
-    Yield,
-    Blocked,
-    Exit,
-}
-
-pub fn invoke_scheduler() {
-    let next = SCHEDULER
-        .try_lock()
-        .and_then(|mut scheduler| scheduler.as_mut().and_then(|s| s.schedule()));
-    if let Some((next_stack_pointer, prev_thread_id)) = next {
-        unsafe {
-            context_switch::context_switch_to(
-                next_stack_pointer,
-                prev_thread_id,
-                SwitchReason::Paused,
-            )
-        };
-    }
-}
-
-pub fn exit_thread() -> ! {
-    synchronous_context_switch(SwitchReason::Exit).expect("can't exit last thread");
-    unreachable!("finished thread continued");
-}
-
-pub fn yield_now() {
-    let _ = synchronous_context_switch(SwitchReason::Yield);
-}
-
-fn synchronous_context_switch(reason: SwitchReason) -> Result<(), ()> {
-    let next = with_scheduler(|s| s.schedule());
-    match next {
-        Some((next_stack_pointer, prev_thread_id)) => unsafe {
-            context_switch::context_switch_to(next_stack_pointer, prev_thread_id, reason);
-            Ok(())
-        },
-        None => Err(()),
-    }
-}
-
-pub fn with_scheduler<F, T>(f: F) -> T
-where
-    F: FnOnce(&mut Scheduler) -> T,
-{
-    f(SCHEDULER.lock().get_or_insert_with(Scheduler::new))
-}

src/multitasking/scheduler.rs

@@ -1,122 +0,0 @@
-use super::SwitchReason;
-use crate::multitasking::thread::{Thread, ThreadId};
-use alloc::collections::{BTreeMap, BTreeSet, VecDeque};
-use core::mem;
-use x86_64::VirtAddr;
-
-pub struct Scheduler {
-    threads: BTreeMap<ThreadId, Thread>,
-    idle_thread_id: Option<ThreadId>,
-    current_thread_id: ThreadId,
-    paused_threads: VecDeque<ThreadId>,
-    blocked_threads: BTreeSet<ThreadId>,
-    wakeups: BTreeSet<ThreadId>,
-}
-
-impl Scheduler {
-    pub fn new() -> Self {
-        let root_thread = Thread::create_root_thread();
-        let root_id = root_thread.id();
-        let mut threads = BTreeMap::new();
-        threads
-            .insert(root_id, root_thread)
-            .expect_none("map is not empty after creation");
-        Scheduler {
-            threads,
-            current_thread_id: root_id,
-            paused_threads: VecDeque::new(),
-            blocked_threads: BTreeSet::new(),
-            wakeups: BTreeSet::new(),
-            idle_thread_id: None,
-        }
-    }
-
-    fn next_thread(&mut self) -> Option<ThreadId> {
-        self.paused_threads.pop_front()
-    }
-
-    pub fn schedule(&mut self) -> Option<(VirtAddr, ThreadId)> {
-        let mut next_thread_id = self.next_thread();
-        if next_thread_id.is_none() && Some(self.current_thread_id) != self.idle_thread_id {
-            next_thread_id = self.idle_thread_id
-        }
-        if let Some(next_id) = next_thread_id {
-            let next_thread = self
-                .threads
-                .get_mut(&next_id)
-                .expect("next thread does not exist");
-            let next_stack_pointer = next_thread
-                .stack_pointer()
-                .take()
-                .expect("paused thread has no stack pointer");
-            let prev_thread_id = mem::replace(&mut self.current_thread_id, next_thread.id());
-            Some((next_stack_pointer, prev_thread_id))
-        } else {
-            None
-        }
-    }
-
-    pub(super) fn add_paused_thread(
-        &mut self,
-        paused_stack_pointer: VirtAddr,
-        paused_thread_id: ThreadId,
-        switch_reason: SwitchReason,
-    ) {
-        let paused_thread = self
-            .threads
-            .get_mut(&paused_thread_id)
-            .expect("paused thread does not exist");
-        paused_thread
-            .stack_pointer()
-            .replace(paused_stack_pointer)
-            .expect_none("running thread should have stack pointer set to None");
-        if Some(paused_thread_id) == self.idle_thread_id {
-            return; // do nothing
-        }
-        match switch_reason {
-            SwitchReason::Paused | SwitchReason::Yield => {
-                self.paused_threads.push_back(paused_thread_id)
-            }
-            SwitchReason::Blocked => {
-                self.blocked_threads.insert(paused_thread_id);
-                self.check_for_wakeup(paused_thread_id);
-            }
-            SwitchReason::Exit => {
-                let thread = self
-                    .threads
-                    .remove(&paused_thread_id)
-                    .expect("thread not found");
-                // TODO: free stack memory again
-            }
-        }
-    }
-
-    pub fn add_new_thread(&mut self, thread: Thread) {
-        let thread_id = thread.id();
-        self.threads
-            .insert(thread_id, thread)
-            .expect_none("thread already exists");
-        self.paused_threads.push_back(thread_id);
-    }
-
-    pub fn set_idle_thread(&mut self, thread: Thread) {
-        let thread_id = thread.id();
-        self.threads
-            .insert(thread_id, thread)
-            .expect_none("thread already exists");
-        self.idle_thread_id
-            .replace(thread_id)
-            .expect_none("idle thread should be set only once");
-    }
-
-    pub fn current_thread_id(&self) -> ThreadId {
-        self.current_thread_id
-    }
-
-    fn check_for_wakeup(&mut self, thread_id: ThreadId) {
-        if self.wakeups.remove(&thread_id) {
-            assert!(self.blocked_threads.remove(&thread_id));
-            self.paused_threads.push_back(thread_id);
-        }
-    }
-}

src/multitasking/thread.rs

@@ -1,82 +0,0 @@
-use crate::memory::{alloc_stack, StackBounds};
-use crate::multitasking::context_switch::Stack;
-use alloc::boxed::Box;
-use x86_64::{
-    structures::paging::{mapper, FrameAllocator, Mapper, Size4KiB},
-    VirtAddr,
-};
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
-pub struct ThreadId(u64);
-
-impl ThreadId {
-    pub fn as_u64(&self) -> u64 {
-        self.0
-    }
-
-    fn new() -> Self {
-        use core::sync::atomic::{AtomicU64, Ordering};
-        static NEXT_THREAD_ID: AtomicU64 = AtomicU64::new(1);
-        ThreadId(NEXT_THREAD_ID.fetch_add(1, Ordering::SeqCst))
-    }
-}
-
-#[derive(Debug)]
-pub struct Thread {
-    id: ThreadId,
-    stack_pointer: Option<VirtAddr>,
-    stack_bounds: Option<StackBounds>,
-}
-
-impl Thread {
-    pub fn create(
-        entry_point: fn() -> !,
-        stack_size: u64,
-        mapper: &mut impl Mapper<Size4KiB>,
-        frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-    ) -> Result<Self, mapper::MapToError> {
-        let stack_bounds = alloc_stack(stack_size, mapper, frame_allocator)?;
-        let mut stack = unsafe { Stack::new(stack_bounds.end()) };
-        stack.set_up_for_entry_point(entry_point);
-        Ok(Self::new(stack.get_stack_pointer(), stack_bounds))
-    }
-
-    pub fn create_from_closure<F>(
-        closure: F,
-        stack_size: u64,
-        mapper: &mut impl Mapper<Size4KiB>,
-        frame_allocator: &mut impl FrameAllocator<Size4KiB>,
-    ) -> Result<Self, mapper::MapToError>
-    where
-        F: FnOnce() -> ! + 'static + Send + Sync,
-    {
-        let stack_bounds = alloc_stack(stack_size, mapper, frame_allocator)?;
-        let mut stack = unsafe { Stack::new(stack_bounds.end()) };
-        stack.set_up_for_closure(Box::new(closure));
-        Ok(Self::new(stack.get_stack_pointer(), stack_bounds))
-    }
-
-    fn new(stack_pointer: VirtAddr, stack_bounds: StackBounds) -> Self {
-        Thread {
-            id: ThreadId::new(),
-            stack_pointer: Some(stack_pointer),
-            stack_bounds: Some(stack_bounds),
-        }
-    }
-
-    pub(super) fn create_root_thread() -> Self {
-        Thread {
-            id: ThreadId(0),
-            stack_pointer: None,
-            stack_bounds: None,
-        }
-    }
-
-    pub fn id(&self) -> ThreadId {
-        self.id
-    }
-
-    pub(super) fn stack_pointer(&mut self) -> &mut Option<VirtAddr> {
-        &mut self.stack_pointer
-    }
-}

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/mod.rs

@@ -0,0 +1,8 @@
+pub(crate) use interrupt_wakeups::interrupt_wake;
+
+pub mod executor;
+mod interrupt_wakeups;
+
+pub fn init() {
+    interrupt_wakeups::init();
+}