Use crossbeam-queue and AtomicWaker for async keypress handling

Cargo.lock

@@ -32,7 +32,9 @@ name = "blog_os"
 version = "0.1.0"
 dependencies = [
  "bootloader",
+ "conquer-once",
  "crossbeam-queue",
+ "futures-util",
  "lazy_static",
  "linked_list_allocator",
  "pc-keyboard",
@@ -64,6 +66,21 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "conquer-once"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f7644600a548ecad74e4a918392af1798f7dd045be610be3203b9e129b4f98f"
+dependencies = [
+ "conquer-util",
+]
+
+[[package]]
+name = "conquer-util"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "654fb2472cc369d311c547103a1fa81d467bef370ae7a0680f65939895b1182a"
+
 [[package]]
 name = "cpuio"
 version = "0.2.0"
@@ -90,6 +107,29 @@ dependencies = [
  "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"
@@ -129,6 +169,12 @@ 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 = "rustc_version"
 version = "0.2.3"

Cargo.toml

@@ -31,6 +31,15 @@ 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 = [
     "-device", "isa-debug-exit,iobase=0xf4,iosize=0x04", "-serial", "stdio",

src/driver/keyboard.rs

@@ -0,0 +1,48 @@
+use crate::{interrupts, print};
+use core::future::Future;
+use core::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use pc_keyboard::{layouts, DecodedKey, Keyboard, ScancodeSet1};
+
+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 = interrupts::SCANCODE_QUEUE
+            .try_get()
+            .expect("scancode queue not initialized");
+        // fast path
+        if let Ok(scancode) = scancodes.pop() {
+            return Poll::Ready(scancode);
+        }
+
+        interrupts::KEYBOARD_INTERRUPT_WAKER.register(&cx.waker());
+        match scancodes.pop() {
+            Ok(scancode) => Poll::Ready(scancode),
+            Err(crossbeam_queue::PopError) => Poll::Pending,
+        }
+    }
+}
+
+pub async fn print_keypresses() {
+    let mut keyboard = Keyboard::new(layouts::Us104Key, ScancodeSet1);
+
+    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 @@
+pub mod keyboard;

src/interrupts.rs

@@ -1,4 +1,8 @@
 use crate::{gdt, hlt_loop, print, println};
+use conquer_once::spin::OnceCell;
+use core::task::Waker;
+use crossbeam_queue::ArrayQueue;
+use futures_util::task::AtomicWaker;
 use lazy_static::lazy_static;
 use pic8259_simple::ChainedPics;
 use spin;
@@ -47,6 +51,23 @@ pub fn init_idt() {
     IDT.load();
 }
 
+pub fn init_queues() {
+    INTERRUPT_WAKEUPS
+        .try_init_once(|| ArrayQueue::new(10))
+        .expect("failed to init interrupt wakeup queue");
+    SCANCODE_QUEUE
+        .try_init_once(|| ArrayQueue::new(10))
+        .expect("failed to init scancode queue");
+}
+
+static INTERRUPT_WAKEUPS: OnceCell<ArrayQueue<Waker>> = OnceCell::uninit();
+
+pub(crate) fn interrupt_wakeups() -> &'static ArrayQueue<Waker> {
+    INTERRUPT_WAKEUPS
+        .try_get()
+        .expect("interrupt wakeup queue not initialized")
+}
+
 extern "x86-interrupt" fn breakpoint_handler(stack_frame: &mut InterruptStackFrame) {
     println!("EXCEPTION: BREAKPOINT\n{:#?}", stack_frame);
 }
@@ -79,26 +100,24 @@ extern "x86-interrupt" fn timer_interrupt_handler(_stack_frame: &mut InterruptSt
     }
 }
 
+pub(crate) static SCANCODE_QUEUE: OnceCell<ArrayQueue<u8>> = OnceCell::uninit();
+pub(crate) static KEYBOARD_INTERRUPT_WAKER: AtomicWaker = AtomicWaker::new();
+
 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),
-            }
+
+    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) = KEYBOARD_INTERRUPT_WAKER.take() {
+        if let Err(_) = interrupt_wakeups().push(waker) {
+            println!("WARNING: dropping interrupt wakeup");
         }
     }
 

src/lib.rs

@@ -7,6 +7,8 @@
 #![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"]
 
@@ -15,6 +17,7 @@ extern crate alloc;
 use core::panic::PanicInfo;
 
 pub mod allocator;
+pub mod driver;
 pub mod gdt;
 pub mod interrupts;
 pub mod memory;
@@ -26,7 +29,6 @@ pub fn init() {
     gdt::init();
     interrupts::init_idt();
     unsafe { interrupts::PICS.lock().initialize() };
-    x86_64::instructions::interrupts::enable();
 }
 
 pub fn test_runner(tests: &[&dyn Fn()]) {

src/main.rs

@@ -26,6 +26,8 @@ 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::interrupts::init_queues();
+    x86_64::instructions::interrupts::enable();
 
     // allocate a number on the heap
     let heap_value = Box::new(41);
@@ -66,6 +68,8 @@ fn kernel_main(boot_info: &'static BootInfo) -> ! {
         println!("It did not crash!");
     });
 
+    spawner.spawn(blog_os::driver::keyboard::print_keypresses());
+
     executor.run();
 }
 

src/task/executor.rs

@@ -1,3 +1,4 @@
+use crate::{interrupts, println};
 use alloc::{boxed::Box, collections::BTreeMap, sync::Arc, task::Wake};
 use core::{
     future::Future,
@@ -34,13 +35,19 @@ impl Executor {
 
     pub fn run(&mut self) -> ! {
         loop {
+            // perform wakeups caused by interrupts
+            // the interrupt handlers can't do it themselves since wakers might execute
+            // arbitrary code, e.g. allocate
+            while let Ok(waker) = interrupts::interrupt_wakeups().pop() {
+                waker.wake();
+            }
             // wakeup waiting tasks
             while let Ok(task_id) = self.wake_queue.pop() {
-                let task = self
-                    .pending_tasks
-                    .remove(&task_id)
-                    .expect("woken task not found in pending_tasks");
-                self.task_queue.push(task);
+                if let Some(task) = self.pending_tasks.remove(&task_id) {
+                    self.task_queue.push(task);
+                } else {
+                    println!("WARNING: woken task not found in pending_tasks");
+                }
             }
             // run ready tasks
             while let Ok(mut task) = self.task_queue.pop() {
@@ -57,7 +64,12 @@ impl Executor {
             }
             // wait for next interrupt if there is nothing left to do
             if self.wake_queue.is_empty() {
-                crate::hlt_loop();
+                unsafe { asm!("cli") };
+                if self.wake_queue.is_empty() {
+                    unsafe { asm!("sti; hlt") };
+                } else {
+                    unsafe { asm!("sti") };
+                }
             }
         }
     }