Make keyboard lock-free (and fix Doom deadlock) by only pushing

scancodes to a spsc queue from the interrupts and only process them
inside syscalls. Also make CURRENT_PID atomic to use less locking

kernel/Cargo.lock

@@ -7,11 +7,13 @@ name = "XunilOS"
 version = "0.1.0"
 dependencies = [
  "font8x8",
+ "heapless",
  "lazy_static",
  "limine",
  "pc-keyboard",
  "pic8259",
  "spin 0.10.0",
+ "static_cell",
  "x86_64",
 ]
 
@@ -27,6 +29,12 @@ version = "2.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1b8e56985ec62d17e9c1001dc89c88ecd7dc08e47eba5ec7c29c7b5eeecde967"
 
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
+
 [[package]]
 name = "const_fn"
 version = "0.4.12"
@@ -39,6 +47,25 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "875488b8711a968268c7cf5d139578713097ca4635a76044e8fe8eedf831d07e"
 
+[[package]]
+name = "hash32"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47d60b12902ba28e2730cd37e95b8c9223af2808df9e902d4df49588d1470606"
+dependencies = [
+ "byteorder",
+]
+
+[[package]]
+name = "heapless"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2af2455f757db2b292a9b1768c4b70186d443bcb3b316252d6b540aec1cd89ed"
+dependencies = [
+ "hash32",
+ "stable_deref_trait",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.5.0"
@@ -81,6 +108,12 @@ dependencies = [
  "x86_64",
 ]
 
+[[package]]
+name = "portable-atomic"
+version = "1.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c33a9471896f1c69cecef8d20cbe2f7accd12527ce60845ff44c153bb2a21b49"
+
 [[package]]
 name = "rustversion"
 version = "1.0.22"
@@ -108,6 +141,21 @@ dependencies = [
  "lock_api",
 ]
 
+[[package]]
+name = "stable_deref_trait"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ce2be8dc25455e1f91df71bfa12ad37d7af1092ae736f3a6cd0e37bc7810596"
+
+[[package]]
+name = "static_cell"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0530892bb4fa575ee0da4b86f86c667132a94b74bb72160f58ee5a4afec74c23"
+dependencies = [
+ "portable-atomic",
+]
+
 [[package]]
 name = "volatile"
 version = "0.4.6"

kernel/Cargo.toml

@@ -10,11 +10,13 @@ bench = false
 
 [dependencies]
 font8x8 = { version = "0.3.1", default-features = false }
+heapless = "0.9.2"
 lazy_static = { version = "1.5.0", features = ["spin_no_std"] }
 limine = "0.5"
 pc-keyboard = "0.8.0"
 pic8259 = "0.11.0"
 spin = "0.10.0"
+static_cell = "2.1.1"
 
 [target.'cfg(target_arch = "x86_64")'.dependencies]
 x86_64 = "0.15.4"

kernel/src/arch/x86_64/interrupts.rs

@@ -1,6 +1,6 @@
 use crate::{
     arch::x86_64::{gdt, mouse::mouse_interrupt},
-    driver::{keyboard::process_keyboard_event, mouse::MOUSE, timer::TIMER},
+    driver::{keyboard::push_scancode, mouse::MOUSE, timer::TIMER},
     println,
 };
 use lazy_static::lazy_static;
@@ -129,7 +129,7 @@ pub extern "x86-interrupt" fn keyboard_interrupt_handler(_stack_frame: Interrupt
     let mut port = Port::new(0x60);
     let scancode: u8 = unsafe { port.read() };
 
-    process_keyboard_event(scancode);
+    push_scancode(scancode);
 
     unsafe {
         PICS.lock()

kernel/src/driver/graphics/framebuffer.rs

@@ -105,5 +105,5 @@ pub fn with_framebuffer<F: FnOnce(&mut Framebuffer)>(f: F) {
         if let Some(fb) = guard.as_mut() {
             f(fb);
         }
-    })
+    });
 }

kernel/src/driver/keyboard.rs

@@ -1,9 +1,9 @@
+use core::sync::atomic::{AtomicU64, Ordering};
+use heapless::spsc::{Consumer, Producer, Queue};
 use pc_keyboard::{DecodedKey, HandleControl, KeyState, Keyboard, ScancodeSet2, layouts};
-use spin::mutex::Mutex;
-use x86_64::instructions::interrupts::without_interrupts;
-
-use crate::task::scheduler::SCHEDULER;
+use static_cell::StaticCell;
 
+use crate::task::scheduler::{SCHEDULER, current_pid};
 #[repr(C)]
 #[derive(Clone, Debug, Copy, Default)]
 pub struct KeyboardEvent {
@@ -15,65 +15,85 @@ pub struct KeyboardEvent {
     pub unicode: u32,
 }
 
-pub fn process_keyboard_event(scancode: u8) {
-    let mut keyboard = without_interrupts(|| KEYBOARD.lock());
+static SCANCODE_QUEUE: StaticCell<Queue<u8, 256>> = StaticCell::new();
+static mut SCANCODE_PROD: Option<Producer<'static, u8>> = None;
+static mut SCANCODE_CONS: Option<Consumer<'static, u8>> = None;
+static mut KEYBOARD: Option<Keyboard<layouts::Us104Key, ScancodeSet2>> = None;
 
-    let scheduler = without_interrupts(|| SCHEDULER.lock());
-    let pid = scheduler.current_process;
+static DROPPED_SCANCODES: AtomicU64 = AtomicU64::new(0);
 
-    if pid < 0 {
-        return;
-    }
+pub fn init_keyboard() {
+    let q = SCANCODE_QUEUE.init(Queue::new());
+    let (p, c) = q.split();
 
-    drop(scheduler);
-
-    if let Ok(Some(key_event)) = keyboard.add_byte(scancode) {
-        let keycode = key_event.code;
-        let keystate = key_event.state;
-        if let Some(key) = keyboard.process_keyevent(key_event) {
-            match key {
-                DecodedKey::Unicode(character) => {
-                    SCHEDULER.with_process(pid as u64, |process| {
-                        process.kbd_buffer.push(KeyboardEvent {
-                            state: if keystate == KeyState::Down { 1 } else { 0 },
-                            _pad1: 0,
-                            key: keycode as u16,
-                            mods: 0,
-                            _pad2: 0,
-                            unicode: character as u32,
-                        })
-                    });
-                }
-                DecodedKey::RawKey(_) => {
-                    SCHEDULER.with_process(pid as u64, |process| {
-                        process.kbd_buffer.push(KeyboardEvent {
-                            state: if keystate == KeyState::Down { 1 } else { 0 },
-                            _pad1: 0,
-                            key: keycode as u16,
-                            mods: 0,
-                            _pad2: 0,
-                            unicode: 0,
-                        })
-                    });
-                }
-            }
-        } else {
-            SCHEDULER.with_process(pid as u64, |process| {
-                process.kbd_buffer.push(KeyboardEvent {
-                    state: if keystate == KeyState::Down { 1 } else { 0 },
-                    _pad1: 0,
-                    key: keycode as u16,
-                    mods: 0,
-                    _pad2: 0,
-                    unicode: 0,
-                })
-            });
-        }
-    }
-}
-
-pub static KEYBOARD: Mutex<Keyboard<layouts::Us104Key, ScancodeSet2>> = Mutex::new(Keyboard::new(
+    unsafe {
+        SCANCODE_PROD = Some(p);
+        SCANCODE_CONS = Some(c);
+        KEYBOARD = Some(Keyboard::new(
             ScancodeSet2::new(),
             layouts::Us104Key,
             HandleControl::Ignore,
-));
+        ))
+    }
+}
+
+pub fn push_scancode(scancode: u8) {
+    let pushed = unsafe {
+        #[allow(static_mut_refs)]
+        match SCANCODE_PROD.as_mut() {
+            Some(prod) => prod.enqueue(scancode).is_ok(),
+            _ => false,
+        }
+    };
+
+    if !pushed {
+        DROPPED_SCANCODES.fetch_add(1, Ordering::Relaxed);
+    }
+}
+
+pub fn process_scancodes() {
+    loop {
+        let scancode = unsafe {
+            #[allow(static_mut_refs)]
+            match SCANCODE_CONS.as_mut() {
+                Some(cons) => match cons.dequeue() {
+                    Some(b) => b,
+                    None => break,
+                },
+                None => break,
+            }
+        };
+
+        if let Some(kbd_event) = process_scancode(scancode) {
+            let pid = current_pid().unwrap_or(0);
+            if pid == 0 {
+                continue;
+            }
+            SCHEDULER.with_process(pid, |process| process.kbd_buffer.push(kbd_event));
+        }
+    }
+}
+
+pub fn process_scancode(scancode: u8) -> Option<KeyboardEvent> {
+    #[allow(static_mut_refs)]
+    let kbd = unsafe { KEYBOARD.as_mut().expect("keyboard not initialized") };
+    if let Ok(Some(key_event)) = kbd.add_byte(scancode) {
+        let keycode = key_event.code;
+        let keystate = key_event.state;
+        let (unicode, state) = match (kbd.process_keyevent(key_event), keystate) {
+            (Some(DecodedKey::Unicode(ch)), st) => (ch as u32, st),
+            _ => (0, keystate),
+        };
+
+        return Some(KeyboardEvent {
+            state: if state == KeyState::Down { 1 } else { 0 },
+            _pad1: 0,
+            key: keycode as u16,
+            mods: 0,
+            _pad2: 0,
+            unicode,
+        });
+    } else {
+        return None;
+    }
+}

kernel/src/driver/serial.rs

@@ -16,7 +16,7 @@ pub struct ConsoleWriter<'a> {
 impl Write for ConsoleWriter<'_> {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         serial_print(s);
-        // self.console.render_text(self.fb, s, 2, false);
+        self.console.render_text(self.fb, s, 2, false);
         Ok(())
     }
 }

kernel/src/driver/syscall.rs

@@ -5,7 +5,6 @@ use core::{
 
 use x86_64::{
     VirtAddr,
-    instructions::interrupts::without_interrupts,
     structures::paging::{FrameAllocator, Mapper, Page, PageTableFlags, Size4KiB},
 };
 
@@ -13,12 +12,12 @@ use crate::{
     arch::arch::{FRAME_ALLOCATOR, get_allocator, infinite_idle, sleep},
     driver::{
         graphics::{framebuffer::with_framebuffer, primitives::rectangle_filled},
-        keyboard::KeyboardEvent,
+        keyboard::{KeyboardEvent, process_scancodes},
         timer::TIMER,
     },
     mm::usercopy::copy_to_user,
     print, println,
-    task::scheduler::SCHEDULER,
+    task::scheduler::{SCHEDULER, current_pid},
     util::align_up,
 };
 
@@ -85,16 +84,14 @@ pub unsafe fn memset(ptr: *mut u8, val: u8, count: usize) {
 }
 
 fn kbd_read(user_ptr: *mut KeyboardEvent, max_events: isize) -> isize {
+    process_scancodes();
     if max_events <= 0 || user_ptr.is_null() {
         return -1;
     }
 
-    let pid = without_interrupts(|| {
-        let scheduler = SCHEDULER.lock();
-        scheduler.current_process
-    });
+    let pid = current_pid().unwrap_or(0);
 
-    if pid < 0 {
+    if pid == 0 {
         return -1;
     }
 
@@ -117,12 +114,11 @@ fn kbd_read(user_ptr: *mut KeyboardEvent, max_events: isize) -> isize {
 }
 
 pub unsafe fn sbrk(increment: isize) -> isize {
-    let scheduler = without_interrupts(|| SCHEDULER.lock());
-    if scheduler.current_process == -1 {
+    let pid = current_pid().unwrap_or(0);
+
+    if pid == 0 {
         return -1;
     }
-    let pid = scheduler.current_process as u64;
-    drop(scheduler);
 
     let mut frame_allocator = FRAME_ALLOCATOR.lock();
     return SCHEDULER

kernel/src/main.rs

@@ -20,6 +20,7 @@ pub mod util;
 use crate::arch::arch::{infinite_idle, init, kernel_crash};
 use crate::driver::graphics::base::rgb;
 use crate::driver::graphics::framebuffer::{init_framebuffer, with_framebuffer};
+use crate::driver::keyboard::init_keyboard;
 use crate::driver::serial::{ConsoleWriter, init_serial_console, with_serial_console};
 use crate::driver::timer::TIMER;
 use crate::userspace_stub::userspace_init;
@@ -105,7 +106,7 @@ unsafe extern "C" fn kmain() -> ! {
             kernel_crash(); // Could not get required info from Limine's memory map.
         }
     } else {
-        kernel_crash(); // Could not get required info from the Limine's higher-half direct mapping.
+        kernel_crash(); // Could not get required info from Limine's higher-half direct mapping.
     }
 
     if let Some(framebuffer_response) = FRAMEBUFFER_REQUEST.get_response() {
@@ -116,6 +117,8 @@ unsafe extern "C" fn kmain() -> ! {
 
     init_serial_console(0, 0);
 
+    init_keyboard();
+
     if let Some(date_at_boot_response) = DATE_AT_BOOT_REQUEST.get_response() {
         TIMER.set_date_at_boot(date_at_boot_response.timestamp().as_secs());
     } else {

kernel/src/task/scheduler.rs

@@ -1,11 +1,27 @@
+use core::sync::atomic::{AtomicU64, Ordering};
+
 use alloc::collections::btree_map::BTreeMap;
 use x86_64::instructions::interrupts::without_interrupts;
 
 use crate::{arch::arch::enter_usermode, task::process::Process, util::Locked};
 
+pub static CURRENT_PID: AtomicU64 = AtomicU64::new(0);
+
+#[inline]
+pub fn current_pid() -> Option<u64> {
+    match CURRENT_PID.load(Ordering::Relaxed) {
+        0 => None,
+        pid => Some(pid),
+    }
+}
+
+#[inline]
+pub fn set_current_pid(pid: Option<u64>) {
+    CURRENT_PID.store(pid.unwrap_or(0), Ordering::Relaxed);
+}
+
 pub struct Scheduler {
     pub processes: BTreeMap<u64, Process>,
-    pub current_process: i64,
     next_pid: u64,
 }
 
@@ -13,7 +29,6 @@ impl Scheduler {
     pub const fn new() -> Scheduler {
         Scheduler {
             processes: BTreeMap::new(),
-            current_process: -1,
             next_pid: 1,
         }
     }
@@ -31,11 +46,12 @@ impl Locked<Scheduler> {
     }
 
     pub fn run_process(&self, pid: u64, entry_point: *const u8) {
-        let mut guard = without_interrupts(|| self.lock());
-        let stack_top = guard.processes[&pid].stack_top;
-        guard.current_process = pid as i64;
+        let stack_top = {
+            let guard = without_interrupts(|| self.lock());
+            guard.processes[&pid].stack_top
+        };
 
-        drop(guard);
+        set_current_pid(Some(pid));
 
         enter_usermode(entry_point as u64, (stack_top & !0xF) - 8);
     }

kernel/src/userspace_stub.rs

@@ -100,11 +100,13 @@ pub fn userspace_init(mapper: &mut OffsetPageTable) -> ! {
     // let mut mouse_x = 100;
     // let mut mouse_y = 100;
 
+    // let mut i = 0;
+
     // loop {
     //     with_serial_console(|serial_console| serial_console.clear(0, 0));
     //     with_framebuffer(|fb| fb.clear(rgb(77, 171, 245)));
-    //     test_performance(|| {
-    //         mouse_status = MOUSE.get_status();
+
+    //     // mouse_status = MOUSE.get_status();
     //     with_framebuffer(|mut fb| {
     //         width = fb.width;
     //         height = fb.height;
@@ -155,7 +157,6 @@ pub fn userspace_init(mapper: &mut OffsetPageTable) -> ! {
 
     //     let (hours, minutes, seconds) =
     //         unix_to_hms(TIMER.get_date_at_boot() + (TIMER.now().elapsed()) / 1000);
-
     //     print!(
     //         "{:?}:{:?}:{:?}\nMouse status: {:?}\nDesktop Size: {:?}",
     //         hours,
@@ -164,10 +165,11 @@ pub fn userspace_init(mapper: &mut OffsetPageTable) -> ! {
     //         mouse_status,
     //         (width, height)
     //     );
-    //     });
+
     //     with_framebuffer(|fb| {
     //         fb.swap();
     //     });
+
     //     sleep(1000 / 165);
     // }
 }