Enable softirq mechanism

Cargo.lock

@@ -54,6 +54,12 @@ dependencies = [
  "spinning_top",
 ]
 
+[[package]]
+name = "array-init"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d62b7694a562cdf5a74227903507c56ab2cc8bdd1f781ed5cb4cf9c9f810bfc"
+
 [[package]]
 name = "arrayvec"
 version = "0.5.2"
@@ -102,6 +108,7 @@ dependencies = [
  "acpi",
  "align_ext",
  "aml",
+ "array-init",
  "aster-main",
  "bit_field",
  "bitflags 1.3.2",

framework/aster-frame/Cargo.toml

@@ -20,7 +20,8 @@ xarray = { git = "https://github.com/asterinas/xarray", rev = "72a4067" }
 int-to-c-enum = { path = "../../kernel/libs/int-to-c-enum" }
 # instrusive-collections of version 0.9.6 fails to compile with current rust toolchain,
 # So we set a fixed version 0.9.5 for this crate
-intrusive-collections = "=0.9.5"
+intrusive-collections = { version = "=0.9.5", features = ["nightly"] }
+array-init = "2.0"
 ktest = { path = "../libs/ktest" }
 id-alloc = { path = "../libs/id-alloc" }
 lazy_static = { version = "1.0", features = ["spin_no_std"] }

framework/aster-frame/src/trap/handler.rs

@@ -18,11 +18,16 @@ pub(crate) fn call_irq_callback_functions(trap_frame: &TrapFrame) {
     for callback_function in callback_functions.iter() {
         callback_function.call(trap_frame);
     }
+    drop(callback_functions);
+
     if !CpuException::is_cpu_exception(trap_frame.trap_num as u16) {
         crate::arch::interrupts_ack();
     }
 
     IN_INTERRUPT_CONTEXT.store(false, Ordering::Release);
+
+    crate::arch::irq::enable_local();
+    crate::trap::softirq::process_pending();
 }
 
 cpu_local! {

framework/aster-frame/src/trap/mod.rs

@@ -2,8 +2,10 @@
 
 mod handler;
 mod irq;
+pub mod softirq;
 
 pub use handler::in_interrupt_context;
+pub use softirq::SoftIrqLine;
 pub use trapframe::TrapFrame;
 
 pub(crate) use self::handler::call_irq_callback_functions;
@@ -15,4 +17,5 @@ pub(crate) fn init() {
     unsafe {
         trapframe::init();
     }
+    softirq::init();
 }

framework/aster-frame/src/trap/softirq.rs

@@ -0,0 +1,163 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use alloc::boxed::Box;
+use core::sync::atomic::{AtomicBool, AtomicU8, Ordering};
+
+use spin::Once;
+
+use crate::{cpu_local, task::disable_preempt, CpuLocal};
+
+/// A representation of a software interrupt (softirq) line.
+///
+/// # Overview
+///
+/// Softirq is an interrupt mechanism in the kernel that enables bottom-half processing;
+/// they are cheaper to execute compared to regular interrupts because softirqs are less
+/// time-critical and thus can be processed in a more flexible manner.
+///
+/// The `SoftIrqLine` struct encapsulates the data and functionality associated with each
+/// softirq line, including an identifier and an associated callback that gets triggered
+/// when the softirq is raised.
+///
+/// The `SoftIrqLine` with the smaller ID has the higher execution priority.
+///
+/// # Example
+///
+/// ```
+/// // Define an unused softirq id.
+/// const MY_SOFTIRQ_ID: u8 = 4;
+/// // Enable the softirq line of this id.
+/// SoftIrqLine::get(MY_SOFTIRQ_ID).enable(|| {
+///     // Define the action to take when the softirq with MY_SOFTIRQ_ID is raised
+///     ...
+/// });
+/// // Later on:
+/// SoftIrqLine::get(MY_SOFTIRQ_ID).raise(); // This will trigger the registered callback
+/// ```
+pub struct SoftIrqLine {
+    id: u8,
+    callback: Once<Box<dyn Fn() + 'static + Sync + Send>>,
+}
+
+impl SoftIrqLine {
+    /// The number of softirq lines.
+    const NR_LINES: u8 = 8;
+
+    /// Gets a softirq line.
+    ///
+    /// The value of `id` must be within `0..NR_LINES`.
+    pub fn get(id: u8) -> &'static SoftIrqLine {
+        &LINES.get().unwrap()[id as usize]
+    }
+
+    const fn new(id: u8) -> Self {
+        Self {
+            id,
+            callback: Once::new(),
+        }
+    }
+
+    /// Gets the ID of this softirq line.
+    pub fn id(&self) -> u8 {
+        self.id
+    }
+
+    /// Raises the softirq, marking it as pending.
+    ///
+    /// If this line is not enabled yet, the method has no effect.
+    pub fn raise(&self) {
+        CpuLocal::borrow_with(&PENDING_MASK, |mask| {
+            mask.fetch_or(1 << self.id, Ordering::Release);
+        });
+    }
+
+    /// Enables a softirq line by registering its callback.
+    ///
+    /// # Panic
+    ///
+    /// Each softirq can only be enabled once.
+    pub fn enable<F>(&self, callback: F)
+    where
+        F: Fn() + 'static + Sync + Send,
+    {
+        assert!(!self.is_enabled());
+
+        self.callback.call_once(|| Box::new(callback));
+        ENABLED_MASK.fetch_or(1 << self.id, Ordering::Release);
+    }
+
+    /// Returns whether this softirq line is enabled.
+    pub fn is_enabled(&self) -> bool {
+        ENABLED_MASK.load(Ordering::Acquire) & (1 << self.id) != 0
+    }
+}
+
+/// A slice that stores the `SoftIrqLine`s, whose ID is equal to its offset in the slice.
+static LINES: Once<[SoftIrqLine; SoftIrqLine::NR_LINES as usize]> = Once::new();
+
+pub(super) fn init() {
+    let lines: [SoftIrqLine; SoftIrqLine::NR_LINES as usize] =
+        array_init::array_init(|i| SoftIrqLine::new(i as u8));
+    LINES.call_once(|| lines);
+}
+
+static ENABLED_MASK: AtomicU8 = AtomicU8::new(0);
+
+cpu_local! {
+    static PENDING_MASK: AtomicU8 = AtomicU8::new(0);
+    static IS_ENABLED: AtomicBool = AtomicBool::new(true);
+}
+
+/// Enables softirq in current processor.
+fn enable_softirq_local() {
+    CpuLocal::borrow_with(&IS_ENABLED, |is_enabled| {
+        is_enabled.store(true, Ordering::Release)
+    })
+}
+
+/// Disables softirq in current processor.
+fn disable_softirq_local() {
+    CpuLocal::borrow_with(&IS_ENABLED, |is_enabled| {
+        is_enabled.store(false, Ordering::Release)
+    })
+}
+
+/// Checks whether the softirq is enabled in current processor.
+fn is_softirq_enabled() -> bool {
+    CpuLocal::borrow_with(&IS_ENABLED, |is_enabled| is_enabled.load(Ordering::Acquire))
+}
+
+/// Processes pending softirqs.
+///
+/// The processing instructions will iterate for `SOFTIRQ_RUN_TIMES` times. If any softirq
+/// is raised during the iteration, it will be processed.
+pub(crate) fn process_pending() {
+    const SOFTIRQ_RUN_TIMES: u8 = 5;
+
+    if !is_softirq_enabled() {
+        return;
+    }
+
+    let preempt_guard = disable_preempt();
+    disable_softirq_local();
+
+    CpuLocal::borrow_with(&PENDING_MASK, |mask| {
+        for i in 0..SOFTIRQ_RUN_TIMES {
+            // will not reactive in this handling.
+            let mut action_mask = {
+                let pending_mask = mask.fetch_and(0, Ordering::Acquire);
+                pending_mask & ENABLED_MASK.load(Ordering::Acquire)
+            };
+
+            if action_mask == 0 {
+                return;
+            }
+            while action_mask > 0 {
+                let action_id = u8::trailing_zeros(action_mask) as u8;
+                SoftIrqLine::get(action_id).callback.get().unwrap()();
+                action_mask &= action_mask - 1;
+            }
+        }
+    });
+    enable_softirq_local();
+}

kernel/aster-nix/src/softirq_id.rs

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: MPL-2.0
+
+//! Defines the used IDs of software interrupt (softirq) lines.
+
+/// The corresponding softirq line is used to schedule urgent taskless jobs.
+pub const TASKLESS_URGENT_SOFTIRQ_ID: u8 = 0;
+
+/// The corresponding softirq line is used to manage timers and handle
+/// time-related jobs.
+pub const TIMER_SOFTIRQ_ID: u8 = 1;
+
+/// The corresponding softirq line is used to schedule general taskless jobs.
+pub const TASKLESS_SOFTIRQ_ID: u8 = 2;

kernel/aster-nix/src/time/clocks/system_wide.rs

@@ -3,17 +3,14 @@
 use alloc::sync::Arc;
 use core::time::Duration;
 
-use aster_frame::{
+use aster_frame::{arch::timer::Jiffies, cpu_local, sync::SpinLock, CpuLocal};
-    arch::timer::{self, Jiffies},
-    cpu_local,
-    sync::SpinLock,
-    CpuLocal,
-};
 use aster_time::read_monotonic_time;
 use paste::paste;
 use spin::Once;
 
-use crate::time::{system_time::START_TIME_AS_DURATION, timer::TimerManager, Clock, SystemTime};
+use crate::time::{
+    self, system_time::START_TIME_AS_DURATION, timer::TimerManager, Clock, SystemTime,
+};
 
 /// The Clock that reads the jiffies, and turn the counter into `Duration`.
 pub struct JiffiesClock {
@@ -220,7 +217,7 @@ macro_rules! define_timer_managers {
                 let callback = move || {
                     clock_manager.process_expired_timers();
                 };
-                timer::register_callback(callback);
+                time::softirq::register_callback(callback);
             )*
         }
     }
@@ -258,7 +255,7 @@ fn init_jiffies_clock_manager() {
     let callback = move || {
         jiffies_timer_manager.process_expired_timers();
     };
-    timer::register_callback(callback);
+    time::softirq::register_callback(callback);
 }
 
 fn update_coarse_clock() {
@@ -270,7 +267,7 @@ fn update_coarse_clock() {
 fn init_coarse_clock() {
     let real_time = RealTimeClock::get().read_time();
     RealTimeCoarseClock::current_ref().call_once(|| SpinLock::new(real_time));
-    timer::register_callback(update_coarse_clock);
+    time::softirq::register_callback(update_coarse_clock);
 }
 
 pub(super) fn init() {

kernel/aster-nix/src/time/mod.rs

@@ -12,6 +12,7 @@ use crate::prelude::*;
 
 pub mod clocks;
 mod core;
+mod softirq;
 mod system_time;
 pub mod wait;
 
@@ -23,6 +24,7 @@ pub type clock_t = i64;
 pub(super) fn init() {
     system_time::init();
     clocks::init();
+    softirq::init();
 }
 
 #[repr(C)]

kernel/aster-nix/src/time/softirq.rs

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MPL-2.0
+
+use alloc::{boxed::Box, vec::Vec};
+
+use aster_frame::{arch::timer, sync::RwLock, trap::SoftIrqLine};
+
+use crate::softirq_id::TIMER_SOFTIRQ_ID;
+
+static TIMER_SOFTIRQ_CALLBACKS: RwLock<Vec<Box<dyn Fn() + Sync + Send>>> = RwLock::new(Vec::new());
+
+pub(super) fn init() {
+    SoftIrqLine::get(TIMER_SOFTIRQ_ID).enable(timer_softirq_handler);
+
+    timer::register_callback(|| {
+        SoftIrqLine::get(TIMER_SOFTIRQ_ID).raise();
+    });
+}
+
+/// Registers a function that will be executed during timer softirq.
+pub(super) fn register_callback<F>(func: F)
+where
+    F: Fn() + Sync + Send + 'static,
+{
+    TIMER_SOFTIRQ_CALLBACKS
+        .write_irq_disabled()
+        .push(Box::new(func));
+}
+
+fn timer_softirq_handler() {
+    let callbacks = TIMER_SOFTIRQ_CALLBACKS.read_irq_disabled();
+    for callback in callbacks.iter() {
+        (callback)();
+    }
+}