Merge time-driver and time-queue-driver traits, make HALs own and handle the queue.

1 files changed, 44 insertions, 111 deletions

diff --git a/embassy-time/src/driver_std.rs b/embassy-time/src/driver_std.rs
index 45467f09b..35888fddd 100644
--- a/embassy-time/src/driver_std.rs
+++ b/embassy-time/src/driver_std.rs
@@ -1,96 +1,66 @@
-use std::cell::{RefCell, UnsafeCell};
-use std::mem::MaybeUninit;
-use std::sync::{Condvar, Mutex, Once};
+use std::sync::{Condvar, Mutex};
+use std::thread;
 use std::time::{Duration as StdDuration, Instant as StdInstant};
-use std::{ptr, thread};
 
-use critical_section::Mutex as CsMutex;
 use embassy_time_driver::Driver;
-use embassy_time_queue_driver::GlobalTimerQueue;
+use embassy_time_queue_driver::Queue;
 
-struct AlarmState {
-    timestamp: u64,
-}
-
-unsafe impl Send for AlarmState {}
-
-impl AlarmState {
-    const fn new() -> Self {
-        Self { timestamp: u64::MAX }
-    }
+struct TimeDriver {
+    signaler: Signaler,
+    inner: Mutex<Inner>,
 }
 
-struct TimeDriver {
-    once: Once,
-    // The STD Driver implementation requires the alarm's mutex to be reentrant, which the STD Mutex isn't
-    // Fortunately, mutexes based on the `critical-section` crate are reentrant, because the critical sections
-    // themselves are reentrant
-    alarm: UninitCell<CsMutex<RefCell<AlarmState>>>,
-    zero_instant: UninitCell<StdInstant>,
-    signaler: UninitCell<Signaler>,
+struct Inner {
+    zero_instant: Option<StdInstant>,
+    queue: Queue,
 }
 
 embassy_time_driver::time_driver_impl!(static DRIVER: TimeDriver = TimeDriver {
-    once: Once::new(),
-    alarm: UninitCell::uninit(),
-    zero_instant: UninitCell::uninit(),
-    signaler: UninitCell::uninit(),
+    inner: Mutex::new(Inner{
+        zero_instant: None,
+        queue: Queue::new(),
+    }),
+    signaler: Signaler::new(),
 });
 
-impl TimeDriver {
-    fn init(&self) {
-        self.once.call_once(|| unsafe {
-            self.alarm
-                .write(CsMutex::new(RefCell::new(const { AlarmState::new() })));
-            self.zero_instant.write(StdInstant::now());
-            self.signaler.write(Signaler::new());
-
-            thread::spawn(Self::alarm_thread);
-        });
+impl Inner {
+    fn init(&mut self) -> StdInstant {
+        *self.zero_instant.get_or_insert_with(|| {
+            thread::spawn(alarm_thread);
+            StdInstant::now()
+        })
     }
+}
 
-    fn alarm_thread() {
-        let zero = unsafe { DRIVER.zero_instant.read() };
-        loop {
-            let now = DRIVER.now();
-
-            let next_alarm = critical_section::with(|cs| {
-                let mut alarm = unsafe { DRIVER.alarm.as_ref() }.borrow_ref_mut(cs);
-                if alarm.timestamp <= now {
-                    alarm.timestamp = u64::MAX;
-
-                    TIMER_QUEUE_DRIVER.dispatch();
-                }
-                alarm.timestamp
-            });
-
-            // Ensure we don't overflow
-            let until = zero
-                .checked_add(StdDuration::from_micros(next_alarm))
-                .unwrap_or_else(|| StdInstant::now() + StdDuration::from_secs(1));
+impl Driver for TimeDriver {
+    fn now(&self) -> u64 {
+        let mut inner = self.inner.lock().unwrap();
+        let zero = inner.init();
+        StdInstant::now().duration_since(zero).as_micros() as u64
+    }
 
-            unsafe { DRIVER.signaler.as_ref() }.wait_until(until);
+    fn schedule_wake(&self, at: u64, waker: &core::task::Waker) {
+        let mut inner = self.inner.lock().unwrap();
+        inner.init();
+        if inner.queue.schedule_wake(at, waker) {
+            self.signaler.signal();
         }
     }
+}
 
-    fn set_alarm(&self, timestamp: u64) -> bool {
-        self.init();
-        critical_section::with(|cs| {
-            let mut alarm = unsafe { self.alarm.as_ref() }.borrow_ref_mut(cs);
-            alarm.timestamp = timestamp;
-            unsafe { self.signaler.as_ref() }.signal();
-        });
+fn alarm_thread() {
+    let zero = DRIVER.inner.lock().unwrap().zero_instant.unwrap();
+    loop {
+        let now = DRIVER.now();
 
-        true
-    }
-}
+        let next_alarm = DRIVER.inner.lock().unwrap().queue.next_expiration(now);
 
-impl Driver for TimeDriver {
-    fn now(&self) -> u64 {
-        self.init();
+        // Ensure we don't overflow
+        let until = zero
+            .checked_add(StdDuration::from_micros(next_alarm))
+            .unwrap_or_else(|| StdInstant::now() + StdDuration::from_secs(1));
 
-        let zero = unsafe { self.zero_instant.read() };
-        StdInstant::now().duration_since(zero).as_micros() as u64
+        DRIVER.signaler.wait_until(until);
     }
 }
 
@@ -100,7 +70,7 @@ struct Signaler {
 }
 
 impl Signaler {
-    fn new() -> Self {
+    const fn new() -> Self {
         Self {
             mutex: Mutex::new(false),
             condvar: Condvar::new(),
@@ -132,40 +102,3 @@ impl Signaler {
         self.condvar.notify_one();
     }
 }
-
-pub(crate) struct UninitCell<T>(MaybeUninit<UnsafeCell<T>>);
-unsafe impl<T> Send for UninitCell<T> {}
-unsafe impl<T> Sync for UninitCell<T> {}
-
-impl<T> UninitCell<T> {
-    pub const fn uninit() -> Self {
-        Self(MaybeUninit::uninit())
-    }
-
-    pub unsafe fn as_ptr(&self) -> *const T {
-        (*self.0.as_ptr()).get()
-    }
-
-    pub unsafe fn as_mut_ptr(&self) -> *mut T {
-        (*self.0.as_ptr()).get()
-    }
-
-    pub unsafe fn as_ref(&self) -> &T {
-        &*self.as_ptr()
-    }
-
-    pub unsafe fn write(&self, val: T) {
-        ptr::write(self.as_mut_ptr(), val)
-    }
-}
-
-impl<T: Copy> UninitCell<T> {
-    pub unsafe fn read(&self) -> T {
-        ptr::read(self.as_mut_ptr())
-    }
-}
-
-embassy_time_queue_driver::timer_queue_impl!(
-    static TIMER_QUEUE_DRIVER: GlobalTimerQueue
-        = GlobalTimerQueue::new(|next_expiration| DRIVER.set_alarm(next_expiration))
-);