4 files changed, 104 insertions, 70 deletions

diff --git a/.gitignore b/.gitignore
index 25d18d5aa..784c6bac0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,3 @@
-/target
+target
 Cargo.lock
 third_party
diff --git a/embassy-std/src/lib.rs b/embassy-std/src/lib.rs
index 2fb814b4d..009ba028d 100644
--- a/embassy-std/src/lib.rs
+++ b/embassy-std/src/lib.rs
@@ -1,9 +1,10 @@
-use embassy::executor::Executor;
+use embassy::executor::{raw, Spawner};
 use embassy::time::TICKS_PER_SECOND;
 use embassy::time::{Alarm, Clock};
-use embassy::util::Forever;
 use rand_core::{OsRng, RngCore};
+use std::marker::PhantomData;
 use std::mem::MaybeUninit;
+use std::ptr;
 use std::sync::{Condvar, Mutex};
 use std::time::{Duration as StdDuration, Instant as StdInstant};
 
@@ -29,7 +30,8 @@ static mut ALARM_AT: u64 = u64::MAX;
 
 pub struct StdAlarm;
 impl Alarm for StdAlarm {
-    fn set_callback(&self, _callback: fn()) {}
+    fn set_callback(&self, _callback: fn(*mut ()), _ctx: *mut ()) {}
+
     fn set(&self, timestamp: u64) {
         unsafe { ALARM_AT = timestamp }
     }
@@ -39,57 +41,91 @@ impl Alarm for StdAlarm {
     }
 }
 
-static EXECUTOR: Forever<Executor> = Forever::new();
-
-lazy_static::lazy_static! {
-    static ref MUTEX: Mutex<bool> = Mutex::new(false);
-    static ref CONDVAR: Condvar = Condvar::new();
+struct Signaler {
+    mutex: Mutex<bool>,
+    condvar: Condvar,
 }
 
-pub fn init() -> &'static Executor {
-    unsafe {
-        CLOCK_ZERO.as_mut_ptr().write(StdInstant::now());
-        embassy::time::set_clock(&StdClock);
-        embassy::rand::set_rand(&StdRand);
-
-        EXECUTOR.put(Executor::new_with_alarm(&StdAlarm, || {
-            let mut signaled = MUTEX.lock().unwrap();
-            *signaled = true;
-            CONDVAR.notify_one();
-        }))
+impl Signaler {
+    fn new() -> Self {
+        Self {
+            mutex: Mutex::new(false),
+            condvar: Condvar::new(),
+        }
     }
-}
 
-pub fn run(executor: &'static Executor) -> ! {
-    unsafe {
-        loop {
-            executor.run();
-
-            let mut signaled = MUTEX.lock().unwrap();
-            while !*signaled {
-                let alarm_at = ALARM_AT;
-                if alarm_at == u64::MAX {
-                    signaled = CONDVAR.wait(signaled).unwrap();
-                } else {
-                    let now = StdClock.now();
-                    if now >= alarm_at {
-                        break;
-                    }
-
-                    let left = alarm_at - now;
-                    let dur = StdDuration::new(
-                        left / (TICKS_PER_SECOND as u64),
-                        (left % (TICKS_PER_SECOND as u64) * 1_000_000_000
-                            / (TICKS_PER_SECOND as u64)) as u32,
-                    );
-                    let (signaled2, timeout) = CONDVAR.wait_timeout(signaled, dur).unwrap();
-                    signaled = signaled2;
-                    if timeout.timed_out() {
-                        break;
-                    }
+    fn wait(&self) {
+        let mut signaled = self.mutex.lock().unwrap();
+        while !*signaled {
+            let alarm_at = unsafe { ALARM_AT };
+            if alarm_at == u64::MAX {
+                signaled = self.condvar.wait(signaled).unwrap();
+            } else {
+                let now = StdClock.now();
+                if now >= alarm_at {
+                    break;
+                }
+
+                let left = alarm_at - now;
+                let dur = StdDuration::new(
+                    left / (TICKS_PER_SECOND as u64),
+                    (left % (TICKS_PER_SECOND as u64) * 1_000_000_000 / (TICKS_PER_SECOND as u64))
+                        as u32,
+                );
+                let (signaled2, timeout) = self.condvar.wait_timeout(signaled, dur).unwrap();
+                signaled = signaled2;
+                if timeout.timed_out() {
+                    break;
                 }
             }
-            *signaled = false;
+        }
+        *signaled = false;
+    }
+
+    fn signal(ctx: *mut ()) {
+        let this = unsafe { &*(ctx as *mut Self) };
+        let mut signaled = this.mutex.lock().unwrap();
+        *signaled = true;
+        this.condvar.notify_one();
+    }
+}
+
+pub struct Executor {
+    inner: raw::Executor,
+    not_send: PhantomData<*mut ()>,
+    signaler: Signaler,
+}
+
+impl Executor {
+    pub fn new() -> Self {
+        unsafe {
+            CLOCK_ZERO.as_mut_ptr().write(StdInstant::now());
+            embassy::time::set_clock(&StdClock);
+            embassy::rand::set_rand(&StdRand);
+        }
+
+        Self {
+            inner: raw::Executor::new(Signaler::signal, ptr::null_mut()),
+            not_send: PhantomData,
+            signaler: Signaler::new(),
+        }
+    }
+
+    pub fn set_alarm(&mut self, alarm: &'static dyn Alarm) {
+        self.inner.set_alarm(alarm);
+    }
+
+    /// Runs the executor.
+    ///
+    /// This function never returns.
+    pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+        self.inner.set_signal_ctx(&self.signaler as *const _ as _);
+
+        init(unsafe { self.inner.spawner() });
+
+        loop {
+            unsafe { self.inner.run_queued() };
+            self.signaler.wait();
         }
     }
 }
diff --git a/embassy/src/executor/mod.rs b/embassy/src/executor/mod.rs
index 7c74fa583..6e4bded09 100644
--- a/embassy/src/executor/mod.rs
+++ b/embassy/src/executor/mod.rs
@@ -113,13 +113,6 @@ pub struct Spawner {
 }
 
 impl Spawner {
-    fn new(executor: &'static raw::Executor) -> Self {
-        Self {
-            executor,
-            not_send: PhantomData,
-        }
-    }
-
     pub fn spawn<F>(&self, token: SpawnToken<F>) -> Result<(), SpawnError> {
         let task = token.raw_task;
         mem::forget(token);
@@ -165,13 +158,6 @@ unsafe impl Sync for SendSpawner {}
 ///
 /// If you want to spawn tasks from another thread, use [SendSpawner].
 impl SendSpawner {
-    fn new(executor: &'static raw::Executor) -> Self {
-        Self {
-            executor,
-            not_send: PhantomData,
-        }
-    }
-
     pub fn spawn<F: Send>(&self, token: SpawnToken<F>) -> Result<(), SpawnError> {
         let header = token.raw_task;
         mem::forget(token);
@@ -207,7 +193,7 @@ impl Executor {
     ///
     /// This function never returns.
     pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
-        init(Spawner::new(&self.inner));
+        init(unsafe { self.inner.spawner() });
 
         loop {
             unsafe { self.inner.run_queued() };
@@ -253,7 +239,7 @@ impl<I: OwnedInterrupt> IrqExecutor<I> {
     pub fn start(&'static mut self, init: impl FnOnce(Spawner) + Send) {
         self.irq.disable();
 
-        init(Spawner::new(&self.inner));
+        init(unsafe { self.inner.spawner() });
 
         self.irq.set_handler(
             |ctx| unsafe {
diff --git a/embassy/src/executor/raw.rs b/embassy/src/executor/raw.rs
index 927b6a421..1f7e48f53 100644
--- a/embassy/src/executor/raw.rs
+++ b/embassy/src/executor/raw.rs
@@ -1,5 +1,6 @@
 use core::cell::Cell;
 use core::cmp::min;
+use core::marker::PhantomData;
 use core::ptr;
 use core::ptr::NonNull;
 use core::sync::atomic::{AtomicU32, Ordering};
@@ -67,7 +68,7 @@ impl Task {
     }
 }
 
-pub(crate) struct Executor {
+pub struct Executor {
     run_queue: RunQueue,
     timer_queue: TimerQueue,
     signal_fn: fn(*mut ()),
@@ -76,7 +77,7 @@ pub(crate) struct Executor {
 }
 
 impl Executor {
-    pub(crate) const fn new(signal_fn: fn(*mut ()), signal_ctx: *mut ()) -> Self {
+    pub const fn new(signal_fn: fn(*mut ()), signal_ctx: *mut ()) -> Self {
         Self {
             run_queue: RunQueue::new(),
             timer_queue: TimerQueue::new(),
@@ -86,23 +87,27 @@ impl Executor {
         }
     }
 
-    pub(crate) fn set_alarm(&mut self, alarm: &'static dyn Alarm) {
+    pub fn set_alarm(&mut self, alarm: &'static dyn Alarm) {
         self.alarm = Some(alarm);
     }
 
+    pub fn set_signal_ctx(&mut self, signal_ctx: *mut ()) {
+        self.signal_ctx = signal_ctx;
+    }
+
     unsafe fn enqueue(&self, item: *mut Task) {
         if self.run_queue.enqueue(item) {
             (self.signal_fn)(self.signal_ctx)
         }
     }
 
-    pub(crate) unsafe fn spawn(&'static self, task: NonNull<Task>) {
+    pub unsafe fn spawn(&'static self, task: NonNull<Task>) {
         let task = task.as_ref();
         task.executor.set(self);
         self.enqueue(task as *const _ as _);
     }
 
-    pub(crate) unsafe fn run_queued(&self) {
+    pub unsafe fn run_queued(&'static self) {
         if self.alarm.is_some() {
             self.timer_queue.dequeue_expired(Instant::now(), |p| {
                 p.as_ref().enqueue();
@@ -138,6 +143,13 @@ impl Executor {
             alarm.set(next_expiration.as_ticks());
         }
     }
+
+    pub unsafe fn spawner(&'static self) -> super::Spawner {
+        super::Spawner {
+            executor: self,
+            not_send: PhantomData,
+        }
+    }
 }
 
 pub use super::waker::task_from_waker;