axtask/
task.rs

1use alloc::{boxed::Box, string::String, sync::Arc};
2use core::ops::Deref;
3use core::sync::atomic::{AtomicBool, AtomicI32, AtomicU8, AtomicU64, Ordering};
4use core::{alloc::Layout, cell::UnsafeCell, fmt, ptr::NonNull};
5
6#[cfg(feature = "preempt")]
7use core::sync::atomic::AtomicUsize;
8
9use kspin::SpinNoIrq;
10use memory_addr::{VirtAddr, align_up_4k};
11
12use axhal::context::TaskContext;
13#[cfg(feature = "tls")]
14use axhal::tls::TlsArea;
15
16use crate::task_ext::AxTaskExt;
17use crate::{AxCpuMask, AxTask, AxTaskRef, WaitQueue};
18
19/// A unique identifier for a thread.
20#[derive(Debug, Clone, Copy, Eq, PartialEq)]
21pub struct TaskId(u64);
22
23/// The possible states of a task.
24#[repr(u8)]
25#[derive(Debug, Clone, Copy, Eq, PartialEq)]
26pub(crate) enum TaskState {
27    /// Task is running on some CPU.
28    Running = 1,
29    /// Task is ready to run on some scheduler's ready queue.
30    Ready = 2,
31    /// Task is blocked (in the wait queue or timer list),
32    /// and it has finished its scheduling process, it can be wake up by `notify()` on any run queue safely.
33    Blocked = 3,
34    /// Task is exited and waiting for being dropped.
35    Exited = 4,
36}
37
38/// The inner task structure.
39pub struct TaskInner {
40    id: TaskId,
41    name: String,
42    is_idle: bool,
43    is_init: bool,
44
45    entry: Option<*mut dyn FnOnce()>,
46    state: AtomicU8,
47
48    /// CPU affinity mask.
49    cpumask: SpinNoIrq<AxCpuMask>,
50
51    /// Mark whether the task is in the wait queue.
52    in_wait_queue: AtomicBool,
53
54    /// Used to indicate whether the task is running on a CPU.
55    #[cfg(feature = "smp")]
56    on_cpu: AtomicBool,
57
58    /// A ticket ID used to identify the timer event.
59    /// Set by `set_timer_ticket()` when creating a timer event in `set_alarm_wakeup()`,
60    /// expired by setting it as zero in `timer_ticket_expired()`, which is called by `cancel_events()`.
61    #[cfg(feature = "irq")]
62    timer_ticket_id: AtomicU64,
63
64    #[cfg(feature = "preempt")]
65    need_resched: AtomicBool,
66    #[cfg(feature = "preempt")]
67    preempt_disable_count: AtomicUsize,
68
69    exit_code: AtomicI32,
70    wait_for_exit: WaitQueue,
71
72    kstack: Option<TaskStack>,
73    ctx: UnsafeCell<TaskContext>,
74    task_ext: AxTaskExt,
75
76    #[cfg(feature = "tls")]
77    tls: TlsArea,
78}
79
80impl TaskId {
81    fn new() -> Self {
82        static ID_COUNTER: AtomicU64 = AtomicU64::new(1);
83        Self(ID_COUNTER.fetch_add(1, Ordering::Relaxed))
84    }
85
86    /// Convert the task ID to a `u64`.
87    pub const fn as_u64(&self) -> u64 {
88        self.0
89    }
90}
91
92impl From<u8> for TaskState {
93    #[inline]
94    fn from(state: u8) -> Self {
95        match state {
96            1 => Self::Running,
97            2 => Self::Ready,
98            3 => Self::Blocked,
99            4 => Self::Exited,
100            _ => unreachable!(),
101        }
102    }
103}
104
105unsafe impl Send for TaskInner {}
106unsafe impl Sync for TaskInner {}
107
108impl TaskInner {
109    /// Create a new task with the given entry function and stack size.
110    pub fn new<F>(entry: F, name: String, stack_size: usize) -> Self
111    where
112        F: FnOnce() + Send + 'static,
113    {
114        let mut t = Self::new_common(TaskId::new(), name);
115        debug!("new task: {}", t.id_name());
116        let kstack = TaskStack::alloc(align_up_4k(stack_size));
117
118        #[cfg(feature = "tls")]
119        let tls = VirtAddr::from(t.tls.tls_ptr() as usize);
120        #[cfg(not(feature = "tls"))]
121        let tls = VirtAddr::from(0);
122
123        t.entry = Some(Box::into_raw(Box::new(entry)));
124        t.ctx_mut().init(task_entry as usize, kstack.top(), tls);
125        t.kstack = Some(kstack);
126        if t.name == "idle" {
127            t.is_idle = true;
128        }
129        t
130    }
131
132    /// Gets the ID of the task.
133    pub const fn id(&self) -> TaskId {
134        self.id
135    }
136
137    /// Gets the name of the task.
138    pub fn name(&self) -> &str {
139        self.name.as_str()
140    }
141
142    /// Get a combined string of the task ID and name.
143    pub fn id_name(&self) -> alloc::string::String {
144        alloc::format!("Task({}, {:?})", self.id.as_u64(), self.name)
145    }
146
147    /// Wait for the task to exit, and return the exit code.
148    ///
149    /// It will return immediately if the task has already exited (but not dropped).
150    pub fn join(&self) -> Option<i32> {
151        self.wait_for_exit
152            .wait_until(|| self.state() == TaskState::Exited);
153        Some(self.exit_code.load(Ordering::Acquire))
154    }
155
156    /// Returns the pointer to the user-defined task extended data.
157    ///
158    /// # Safety
159    ///
160    /// The caller should not access the pointer directly, use [`TaskExtRef::task_ext`]
161    /// or [`TaskExtMut::task_ext_mut`] instead.
162    ///
163    /// [`TaskExtRef::task_ext`]: crate::task_ext::TaskExtRef::task_ext
164    /// [`TaskExtMut::task_ext_mut`]: crate::task_ext::TaskExtMut::task_ext_mut
165    pub unsafe fn task_ext_ptr(&self) -> *mut u8 {
166        self.task_ext.as_ptr()
167    }
168
169    /// Initialize the user-defined task extended data.
170    ///
171    /// Returns a reference to the task extended data if it has not been
172    /// initialized yet (empty), otherwise returns [`None`].
173    pub fn init_task_ext<T: Sized>(&mut self, data: T) -> Option<&T> {
174        if self.task_ext.is_empty() {
175            self.task_ext.write(data).map(|data| &*data)
176        } else {
177            None
178        }
179    }
180
181    /// Returns a mutable reference to the task context.
182    #[inline]
183    pub const fn ctx_mut(&mut self) -> &mut TaskContext {
184        self.ctx.get_mut()
185    }
186
187    /// Returns the top address of the kernel stack.
188    #[inline]
189    pub const fn kernel_stack_top(&self) -> Option<VirtAddr> {
190        match &self.kstack {
191            Some(s) => Some(s.top()),
192            None => None,
193        }
194    }
195
196    /// Gets the cpu affinity mask of the task.
197    ///
198    /// Returns the cpu affinity mask of the task in type [`AxCpuMask`].
199    #[inline]
200    pub fn cpumask(&self) -> AxCpuMask {
201        *self.cpumask.lock()
202    }
203
204    /// Sets the cpu affinity mask of the task.
205    ///
206    /// # Arguments
207    /// `cpumask` - The cpu affinity mask to be set in type [`AxCpuMask`].
208    #[inline]
209    pub fn set_cpumask(&self, cpumask: AxCpuMask) {
210        *self.cpumask.lock() = cpumask
211    }
212}
213
214// private methods
215impl TaskInner {
216    fn new_common(id: TaskId, name: String) -> Self {
217        Self {
218            id,
219            name,
220            is_idle: false,
221            is_init: false,
222            entry: None,
223            state: AtomicU8::new(TaskState::Ready as u8),
224            // By default, the task is allowed to run on all CPUs.
225            cpumask: SpinNoIrq::new(AxCpuMask::full()),
226            in_wait_queue: AtomicBool::new(false),
227            #[cfg(feature = "irq")]
228            timer_ticket_id: AtomicU64::new(0),
229            #[cfg(feature = "smp")]
230            on_cpu: AtomicBool::new(false),
231            #[cfg(feature = "preempt")]
232            need_resched: AtomicBool::new(false),
233            #[cfg(feature = "preempt")]
234            preempt_disable_count: AtomicUsize::new(0),
235            exit_code: AtomicI32::new(0),
236            wait_for_exit: WaitQueue::new(),
237            kstack: None,
238            ctx: UnsafeCell::new(TaskContext::new()),
239            task_ext: AxTaskExt::empty(),
240            #[cfg(feature = "tls")]
241            tls: TlsArea::alloc(),
242        }
243    }
244
245    /// Creates an "init task" using the current CPU states, to use as the
246    /// current task.
247    ///
248    /// As it is the current task, no other task can switch to it until it
249    /// switches out.
250    ///
251    /// And there is no need to set the `entry`, `kstack` or `tls` fields, as
252    /// they will be filled automatically when the task is switches out.
253    pub(crate) fn new_init(name: String) -> Self {
254        let mut t = Self::new_common(TaskId::new(), name);
255        t.is_init = true;
256        #[cfg(feature = "smp")]
257        t.set_on_cpu(true);
258        if t.name == "idle" {
259            t.is_idle = true;
260        }
261        t
262    }
263
264    pub(crate) fn into_arc(self) -> AxTaskRef {
265        Arc::new(AxTask::new(self))
266    }
267
268    #[inline]
269    pub(crate) fn state(&self) -> TaskState {
270        self.state.load(Ordering::Acquire).into()
271    }
272
273    #[inline]
274    pub(crate) fn set_state(&self, state: TaskState) {
275        self.state.store(state as u8, Ordering::Release)
276    }
277
278    /// Transition the task state from `current_state` to `new_state`,
279    /// Returns `true` if the current state is `current_state` and the state is successfully set to `new_state`,
280    /// otherwise returns `false`.
281    #[inline]
282    pub(crate) fn transition_state(&self, current_state: TaskState, new_state: TaskState) -> bool {
283        self.state
284            .compare_exchange(
285                current_state as u8,
286                new_state as u8,
287                Ordering::AcqRel,
288                Ordering::Acquire,
289            )
290            .is_ok()
291    }
292
293    #[inline]
294    pub(crate) fn is_running(&self) -> bool {
295        matches!(self.state(), TaskState::Running)
296    }
297
298    #[inline]
299    pub(crate) fn is_ready(&self) -> bool {
300        matches!(self.state(), TaskState::Ready)
301    }
302
303    #[inline]
304    pub(crate) const fn is_init(&self) -> bool {
305        self.is_init
306    }
307
308    #[inline]
309    pub(crate) const fn is_idle(&self) -> bool {
310        self.is_idle
311    }
312
313    #[inline]
314    pub(crate) fn in_wait_queue(&self) -> bool {
315        self.in_wait_queue.load(Ordering::Acquire)
316    }
317
318    #[inline]
319    pub(crate) fn set_in_wait_queue(&self, in_wait_queue: bool) {
320        self.in_wait_queue.store(in_wait_queue, Ordering::Release);
321    }
322
323    /// Returns task's current timer ticket ID.
324    #[inline]
325    #[cfg(feature = "irq")]
326    pub(crate) fn timer_ticket(&self) -> u64 {
327        self.timer_ticket_id.load(Ordering::Acquire)
328    }
329
330    /// Set the timer ticket ID.
331    #[inline]
332    #[cfg(feature = "irq")]
333    pub(crate) fn set_timer_ticket(&self, timer_ticket_id: u64) {
334        // CAN NOT set timer_ticket_id to 0,
335        // because 0 is used to indicate the timer event is expired.
336        assert!(timer_ticket_id != 0);
337        self.timer_ticket_id
338            .store(timer_ticket_id, Ordering::Release);
339    }
340
341    /// Expire timer ticket ID by setting it to 0,
342    /// it can be used to identify one timer event is triggered or expired.
343    #[inline]
344    #[cfg(feature = "irq")]
345    pub(crate) fn timer_ticket_expired(&self) {
346        self.timer_ticket_id.store(0, Ordering::Release);
347    }
348
349    #[inline]
350    #[cfg(feature = "preempt")]
351    pub(crate) fn set_preempt_pending(&self, pending: bool) {
352        self.need_resched.store(pending, Ordering::Release)
353    }
354
355    #[inline]
356    #[cfg(feature = "preempt")]
357    pub(crate) fn can_preempt(&self, current_disable_count: usize) -> bool {
358        self.preempt_disable_count.load(Ordering::Acquire) == current_disable_count
359    }
360
361    #[inline]
362    #[cfg(feature = "preempt")]
363    pub(crate) fn disable_preempt(&self) {
364        self.preempt_disable_count.fetch_add(1, Ordering::Release);
365    }
366
367    #[inline]
368    #[cfg(feature = "preempt")]
369    pub(crate) fn enable_preempt(&self, resched: bool) {
370        if self.preempt_disable_count.fetch_sub(1, Ordering::Release) == 1 && resched {
371            // If current task is pending to be preempted, do rescheduling.
372            Self::current_check_preempt_pending();
373        }
374    }
375
376    #[cfg(feature = "preempt")]
377    fn current_check_preempt_pending() {
378        use kernel_guard::NoPreemptIrqSave;
379        let curr = crate::current();
380        if curr.need_resched.load(Ordering::Acquire) && curr.can_preempt(0) {
381            // Note: if we want to print log msg during `preempt_resched`, we have to
382            // disable preemption here, because the axlog may cause preemption.
383            let mut rq = crate::current_run_queue::<NoPreemptIrqSave>();
384            if curr.need_resched.load(Ordering::Acquire) {
385                rq.preempt_resched()
386            }
387        }
388    }
389
390    /// Notify all tasks that join on this task.
391    pub(crate) fn notify_exit(&self, exit_code: i32) {
392        self.exit_code.store(exit_code, Ordering::Release);
393        self.wait_for_exit.notify_all(false);
394    }
395
396    #[inline]
397    pub(crate) const unsafe fn ctx_mut_ptr(&self) -> *mut TaskContext {
398        self.ctx.get()
399    }
400
401    /// Returns whether the task is running on a CPU.
402    ///
403    /// It is used to protect the task from being moved to a different run queue
404    /// while it has not finished its scheduling process.
405    /// The `on_cpu field is set to `true` when the task is preparing to run on a CPU,
406    /// and it is set to `false` when the task has finished its scheduling process in `clear_prev_task_on_cpu()`.
407    #[cfg(feature = "smp")]
408    #[inline]
409    pub(crate) fn on_cpu(&self) -> bool {
410        self.on_cpu.load(Ordering::Acquire)
411    }
412
413    /// Sets whether the task is running on a CPU.
414    #[cfg(feature = "smp")]
415    #[inline]
416    pub(crate) fn set_on_cpu(&self, on_cpu: bool) {
417        self.on_cpu.store(on_cpu, Ordering::Release)
418    }
419}
420
421impl fmt::Debug for TaskInner {
422    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
423        f.debug_struct("TaskInner")
424            .field("id", &self.id)
425            .field("name", &self.name)
426            .field("state", &self.state())
427            .finish()
428    }
429}
430
431impl Drop for TaskInner {
432    fn drop(&mut self) {
433        debug!("task drop: {}", self.id_name());
434    }
435}
436
437struct TaskStack {
438    ptr: NonNull<u8>,
439    layout: Layout,
440}
441
442impl TaskStack {
443    pub fn alloc(size: usize) -> Self {
444        let layout = Layout::from_size_align(size, 16).unwrap();
445        Self {
446            ptr: NonNull::new(unsafe { alloc::alloc::alloc(layout) }).unwrap(),
447            layout,
448        }
449    }
450
451    pub const fn top(&self) -> VirtAddr {
452        unsafe { core::mem::transmute(self.ptr.as_ptr().add(self.layout.size())) }
453    }
454}
455
456impl Drop for TaskStack {
457    fn drop(&mut self) {
458        unsafe { alloc::alloc::dealloc(self.ptr.as_ptr(), self.layout) }
459    }
460}
461
462use core::mem::ManuallyDrop;
463
464/// A wrapper of [`AxTaskRef`] as the current task.
465///
466/// It won't change the reference count of the task when created or dropped.
467pub struct CurrentTask(ManuallyDrop<AxTaskRef>);
468
469impl CurrentTask {
470    pub(crate) fn try_get() -> Option<Self> {
471        let ptr: *const super::AxTask = axhal::cpu::current_task_ptr();
472        if !ptr.is_null() {
473            Some(Self(unsafe { ManuallyDrop::new(AxTaskRef::from_raw(ptr)) }))
474        } else {
475            None
476        }
477    }
478
479    pub(crate) fn get() -> Self {
480        Self::try_get().expect("current task is uninitialized")
481    }
482
483    /// Converts [`CurrentTask`] to [`AxTaskRef`].
484    pub fn as_task_ref(&self) -> &AxTaskRef {
485        &self.0
486    }
487
488    pub(crate) fn clone(&self) -> AxTaskRef {
489        self.0.deref().clone()
490    }
491
492    pub(crate) fn ptr_eq(&self, other: &AxTaskRef) -> bool {
493        Arc::ptr_eq(&self.0, other)
494    }
495
496    pub(crate) unsafe fn init_current(init_task: AxTaskRef) {
497        assert!(init_task.is_init());
498        #[cfg(feature = "tls")]
499        axhal::asm::write_thread_pointer(init_task.tls.tls_ptr() as usize);
500        let ptr = Arc::into_raw(init_task);
501        unsafe {
502            axhal::cpu::set_current_task_ptr(ptr);
503        }
504    }
505
506    pub(crate) unsafe fn set_current(prev: Self, next: AxTaskRef) {
507        let Self(arc) = prev;
508        ManuallyDrop::into_inner(arc); // `call Arc::drop()` to decrease prev task reference count.
509        let ptr = Arc::into_raw(next);
510        unsafe {
511            axhal::cpu::set_current_task_ptr(ptr);
512        }
513    }
514}
515
516impl Deref for CurrentTask {
517    type Target = TaskInner;
518    fn deref(&self) -> &Self::Target {
519        self.0.deref()
520    }
521}
522
523extern "C" fn task_entry() -> ! {
524    #[cfg(feature = "smp")]
525    unsafe {
526        // Clear the prev task on CPU before running the task entry function.
527        crate::run_queue::clear_prev_task_on_cpu();
528    }
529    // Enable irq (if feature "irq" is enabled) before running the task entry function.
530    #[cfg(feature = "irq")]
531    axhal::asm::enable_irqs();
532    let task = crate::current();
533    if let Some(entry) = task.entry {
534        unsafe { Box::from_raw(entry)() };
535    }
536    crate::exit(0);
537}
axtask/task.rs

axtask/
task.rs
