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Change time Driver contract to never fire the alarm synchronously

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This commit is contained in:
ivmarkov 2022-10-24 09:17:43 +03:00
parent 53608a87ac
commit 4d5550070f
8 changed files with 113 additions and 117 deletions
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78
embassy-executor/src/raw/mod.rs
View File

@ -354,46 +354,54 @@ impl Executor {
/// somehow schedule for `poll()` to be called later, at a time you know for sure there's
/// no `poll()` already running.
pub unsafe fn poll(&'static self) {
#[cfg(feature = "integrated-timers")]
self.timer_queue.dequeue_expired(Instant::now(), |task| wake_task(task));
loop {
#[cfg(feature = "integrated-timers")]
self.timer_queue.dequeue_expired(Instant::now(), |task| wake_task(task));
self.run_queue.dequeue_all(|p| {
let task = p.as_ref();
self.run_queue.dequeue_all(|p| {
let task = p.as_ref();
#[cfg(feature = "integrated-timers")]
task.expires_at.set(Instant::MAX);
let state = task.state.fetch_and(!STATE_RUN_QUEUED, Ordering::AcqRel);
if state & STATE_SPAWNED == 0 {
// If task is not running, ignore it. This can happen in the following scenario:
// - Task gets dequeued, poll starts
// - While task is being polled, it gets woken. It gets placed in the queue.
// - Task poll finishes, returning done=true
// - RUNNING bit is cleared, but the task is already in the queue.
return;
}
#[cfg(feature = "rtos-trace")]
trace::task_exec_begin(p.as_ptr() as u32);
// Run the task
task.poll_fn.read()(p as _);
#[cfg(feature = "rtos-trace")]
trace::task_exec_end();
// Enqueue or update into timer_queue
#[cfg(feature = "integrated-timers")]
self.timer_queue.update(p);
});
#[cfg(feature = "integrated-timers")]
task.expires_at.set(Instant::MAX);
let state = task.state.fetch_and(!STATE_RUN_QUEUED, Ordering::AcqRel);
if state & STATE_SPAWNED == 0 {
// If task is not running, ignore it. This can happen in the following scenario:
// - Task gets dequeued, poll starts
// - While task is being polled, it gets woken. It gets placed in the queue.
// - Task poll finishes, returning done=true
// - RUNNING bit is cleared, but the task is already in the queue.
return;
{
// If this is already in the past, set_alarm might return false
// In that case do another poll loop iteration.
let next_expiration = self.timer_queue.next_expiration();
if driver::set_alarm(self.alarm, next_expiration.as_ticks()) {
break;
}
}
#[cfg(feature = "rtos-trace")]
trace::task_exec_begin(p.as_ptr() as u32);
// Run the task
task.poll_fn.read()(p as _);
#[cfg(feature = "rtos-trace")]
trace::task_exec_end();
// Enqueue or update into timer_queue
#[cfg(feature = "integrated-timers")]
self.timer_queue.update(p);
});
#[cfg(feature = "integrated-timers")]
{
// If this is already in the past, set_alarm will immediately trigger the alarm.
// This will cause `signal_fn` to be called, which will cause `poll()` to be called again,
// so we immediately do another poll loop iteration.
let next_expiration = self.timer_queue.next_expiration();
driver::set_alarm(self.alarm, next_expiration.as_ticks());
#[cfg(not(feature = "integrated-timers"))]
{
break;
}
}
#[cfg(feature = "rtos-trace")]

19
embassy-nrf/src/time_driver.rs
View File

@ -243,20 +243,19 @@ impl Driver for RtcDriver {
})
}
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
critical_section::with(|cs| {
let t = self.now();
// If alarm timestamp has passed don't set the alarm and return `false` to indicate that.
if timestamp <= t {
return false;
}
let n = alarm.id() as _;
let alarm = self.get_alarm(cs, alarm);
alarm.timestamp.set(timestamp);
let t = self.now();
// If alarm timestamp has passed, trigger it instantly.
if timestamp <= t {
self.trigger_alarm(n, cs);
return;
}
let r = rtc();
// If it hasn't triggered yet, setup it in the compare channel.
@ -287,6 +286,8 @@ impl Driver for RtcDriver {
// It will be setup later by `next_period`.
r.intenclr.write(|w| unsafe { w.bits(compare_n(n)) });
}
true
})
}
}

17
embassy-rp/src/timer.rs
View File

@ -68,9 +68,16 @@ impl Driver for TimerDriver {
})
}
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
let n = alarm.id() as usize;
critical_section::with(|cs| {
let now = self.now();
// If alarm timestamp has passed don't set the alarm and return `false` to indicate that.
if timestamp <= now {
return false;
}
let alarm = &self.alarms.borrow(cs)[n];
alarm.timestamp.set(timestamp);
@ -80,13 +87,7 @@ impl Driver for TimerDriver {
// it is checked if the alarm time has passed.
unsafe { pac::TIMER.alarm(n).write_value(timestamp as u32) };
let now = self.now();
// If alarm timestamp has passed, trigger it instantly.
// This disarms it.
if timestamp <= now {
self.trigger_alarm(n, cs);
}
true
})
}
}

18
embassy-stm32/src/time_driver.rs
View File

@ -292,21 +292,21 @@ impl Driver for RtcDriver {
})
}
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
critical_section::with(|cs| {
let t = self.now();
// If alarm timestamp has passed don't set the alarm and return `false` to indicate that.
if timestamp <= t {
return false;
}
let r = T::regs_gp16();
let n = alarm.id() as _;
let alarm = self.get_alarm(cs, alarm);
alarm.timestamp.set(timestamp);
let t = self.now();
if timestamp <= t {
unsafe { r.dier().modify(|w| w.set_ccie(n + 1, false)) };
self.trigger_alarm(n, cs);
return;
}
let safe_timestamp = timestamp.max(t + 3);
// Write the CCR value regardless of whether we're going to enable it now or not.
@ -317,6 +317,8 @@ impl Driver for RtcDriver {
let diff = timestamp - t;
// NOTE(unsafe) We're in a critical section
unsafe { r.dier().modify(|w| w.set_ccie(n + 1, diff < 0xc000)) };
true
})
}
}

13
embassy-time/src/driver.rs
View File

@ -105,20 +105,21 @@ pub trait Driver: Send + Sync + 'static {
/// Sets an alarm at the given timestamp. When the current timestamp reaches the alarm
/// timestamp, the provided callback function will be called.
///
/// If `timestamp` is already in the past, the alarm callback must be immediately fired.
/// In this case, it is allowed (but not mandatory) to call the alarm callback synchronously from `set_alarm`.
/// The `Driver` implementation should guarantee that the alarm callback is never called synchronously from `set_alarm`.
/// Rather - if `timestamp` is already in the past - `false` should be returned and alarm should not be set,
/// or alternatively, the driver should return `true` and arrange to call the alarm callback as soon as possible, but not synchronously.
///
/// When callback is called, it is guaranteed that now() will return a value greater or equal than timestamp.
///
/// Only one alarm can be active at a time for each AlarmHandle. This overwrites any previously-set alarm if any.
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64);
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool;
}
extern "Rust" {
fn _embassy_time_now() -> u64;
fn _embassy_time_allocate_alarm() -> Option<AlarmHandle>;
fn _embassy_time_set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ());
fn _embassy_time_set_alarm(alarm: AlarmHandle, timestamp: u64);
fn _embassy_time_set_alarm(alarm: AlarmHandle, timestamp: u64) -> bool;
}
/// See [`Driver::now`]
@ -139,7 +140,7 @@ pub fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut (
}
/// See [`Driver::set_alarm`]
pub fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
pub fn set_alarm(alarm: AlarmHandle, timestamp: u64) -> bool {
unsafe { _embassy_time_set_alarm(alarm, timestamp) }
}
@ -167,7 +168,7 @@ macro_rules! time_driver_impl {
}
#[no_mangle]
fn _embassy_time_set_alarm(alarm: $crate::driver::AlarmHandle, timestamp: u64) {
fn _embassy_time_set_alarm(alarm: $crate::driver::AlarmHandle, timestamp: u64) -> bool {
<$t as $crate::driver::Driver>::set_alarm(&$name, alarm, timestamp)
}
};

4
embassy-time/src/driver_std.rs
View File

@ -127,12 +127,14 @@ impl Driver for TimeDriver {
alarm.ctx = ctx;
}
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
self.init();
let mut alarms = unsafe { self.alarms.as_ref() }.lock().unwrap();
let alarm = &mut alarms[alarm.id() as usize];
alarm.timestamp = timestamp;
unsafe { self.signaler.as_ref() }.signal();
true
}
}

4
embassy-time/src/driver_wasm.rs
View File

@ -81,13 +81,15 @@ impl Driver for TimeDriver {
}
}
fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) -> bool {
self.init();
let mut alarms = unsafe { self.alarms.as_ref() }.lock().unwrap();
let alarm = &mut alarms[alarm.id() as usize];
alarm.closure.replace(Closure::new(move || {
callback(ctx);
}));
true
}
fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {

77
embassy-time/src/queue_generic.rs
View File

@ -2,7 +2,6 @@ use core::cell::RefCell;
use core::cmp::Ordering;
use core::task::Waker;
use atomic_polyfill::{AtomicU64, Ordering as AtomicOrdering};
use embassy_sync::blocking_mutex::raw::CriticalSectionRawMutex;
use embassy_sync::blocking_mutex::Mutex;
use heapless::sorted_linked_list::{LinkedIndexU8, Min, SortedLinkedList};
@ -71,7 +70,7 @@ impl InnerQueue {
}
}
fn schedule_wake(&mut self, at: Instant, waker: &Waker, alarm_schedule: &AtomicU64) {
fn schedule_wake(&mut self, at: Instant, waker: &Waker) {
self.queue
.find_mut(|timer| timer.waker.will_wake(waker))
.map(|mut timer| {
@ -98,50 +97,54 @@ impl InnerQueue {
// dispatch all timers that are already due
//
// Then update the alarm if necessary
self.dispatch(alarm_schedule);
self.dispatch();
}
fn dispatch(&mut self, alarm_schedule: &AtomicU64) {
let now = Instant::now();
fn dispatch(&mut self) {
loop {
let now = Instant::now();
while self.queue.peek().filter(|timer| timer.at <= now).is_some() {
self.queue.pop().unwrap().waker.wake();
while self.queue.peek().filter(|timer| timer.at <= now).is_some() {
self.queue.pop().unwrap().waker.wake();
}
if self.update_alarm() {
break;
}
}
self.update_alarm(alarm_schedule);
}
fn update_alarm(&mut self, alarm_schedule: &AtomicU64) {
fn update_alarm(&mut self) -> bool {
if let Some(timer) = self.queue.peek() {
let new_at = timer.at;
if self.alarm_at != new_at {
self.alarm_at = new_at;
alarm_schedule.store(new_at.as_ticks(), AtomicOrdering::SeqCst);
return set_alarm(self.alarm.unwrap(), self.alarm_at.as_ticks());
}
} else {
self.alarm_at = Instant::MAX;
alarm_schedule.store(Instant::MAX.as_ticks(), AtomicOrdering::SeqCst);
}
true
}
fn handle_alarm(&mut self, alarm_schedule: &AtomicU64) {
fn handle_alarm(&mut self) {
self.alarm_at = Instant::MAX;
self.dispatch(alarm_schedule);
self.dispatch();
}
}
struct Queue {
inner: Mutex<CriticalSectionRawMutex, RefCell<InnerQueue>>,
alarm_schedule: AtomicU64,
}
impl Queue {
const fn new() -> Self {
Self {
inner: Mutex::new(RefCell::new(InnerQueue::new())),
alarm_schedule: AtomicU64::new(u64::MAX),
}
}
@ -156,28 +159,12 @@ impl Queue {
set_alarm_callback(handle, Self::handle_alarm_callback, self as *const _ as _);
}
inner.schedule_wake(at, waker, &self.alarm_schedule)
inner.schedule_wake(at, waker)
});
self.update_alarm();
}
fn update_alarm(&self) {
// Need to set the alarm when we are *not* holding the mutex on the inner queue
// because mutexes are not re-entrant, which is a problem because `set_alarm` might immediately
// call us back if the timestamp is in the past.
let alarm_at = self.alarm_schedule.swap(u64::MAX, AtomicOrdering::SeqCst);
if alarm_at < u64::MAX {
set_alarm(self.inner.lock(|inner| inner.borrow().alarm.unwrap()), alarm_at);
}
}
fn handle_alarm(&self) {
self.inner
.lock(|inner| inner.borrow_mut().handle_alarm(&self.alarm_schedule));
self.update_alarm();
self.inner.lock(|inner| inner.borrow_mut().handle_alarm());
}
fn handle_alarm_callback(ctx: *mut ()) {
@ -196,7 +183,6 @@ crate::timer_queue_impl!(static QUEUE: Queue = Queue::new());
#[cfg(test)]
mod tests {
use core::cell::Cell;
use core::sync::atomic::Ordering;
use core::task::{RawWaker, RawWakerVTable, Waker};
use std::rc::Rc;
use std::sync::Mutex;
@ -282,20 +268,14 @@ mod tests {
inner.ctx = ctx;
}
fn set_alarm(&self, _alarm: AlarmHandle, timestamp: u64) {
let notify = {
let mut inner = self.0.lock().unwrap();
fn set_alarm(&self, _alarm: AlarmHandle, timestamp: u64) -> bool {
let mut inner = self.0.lock().unwrap();
if timestamp <= inner.now {
Some((inner.callback, inner.ctx))
} else {
inner.alarm = timestamp;
None
}
};
if let Some((callback, ctx)) = notify {
(callback)(ctx);
if timestamp <= inner.now {
false
} else {
inner.alarm = timestamp;
true
}
}
}
@ -344,7 +324,6 @@ mod tests {
fn setup() {
DRIVER.reset();
QUEUE.alarm_schedule.store(u64::MAX, Ordering::SeqCst);
QUEUE.inner.lock(|inner| {
*inner.borrow_mut() = InnerQueue::new();
});