Split waker to separate file.

embassy/src/executor/mod.rs

@@ -8,16 +8,17 @@ use core::pin::Pin;
 use core::ptr;
 use core::ptr::NonNull;
 use core::sync::atomic::{AtomicU32, Ordering};
-use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+use core::task::{Context, Poll, RawWaker, Waker};
 
 mod run_queue;
 mod util;
+mod waker;
 
 use self::run_queue::{RunQueue, RunQueueItem};
 use self::util::UninitCell;
 
-/// Task is spawned and future hasn't finished running yet.
-const STATE_RUNNING: u32 = 1 << 0;
+/// Task is spawned (has a future)
+const STATE_SPAWNED: u32 = 1 << 0;
 /// Task is in the executor run queue
 const STATE_RUN_QUEUED: u32 = 1 << 1;
 /// Task is in the executor timer queue
@@ -27,7 +28,36 @@ pub(crate) struct TaskHeader {
     state: AtomicU32,
     run_queue_item: RunQueueItem,
     executor: Cell<*const Executor>, // Valid if state != 0
-    poll_fn: UninitCell<unsafe fn(*mut TaskHeader)>, // Valid if STATE_RUNNING
+    poll_fn: UninitCell<unsafe fn(*mut TaskHeader)>, // Valid if STATE_SPAWNED
+}
+
+impl TaskHeader {
+    pub(crate) unsafe fn enqueue(&self) {
+        let mut current = self.state.load(Ordering::Acquire);
+        loop {
+            // If already scheduled, or if not started,
+            if (current & STATE_RUN_QUEUED != 0) || (current & STATE_SPAWNED == 0) {
+                return;
+            }
+
+            // Mark it as scheduled
+            let new = current | STATE_RUN_QUEUED;
+
+            match self.state.compare_exchange_weak(
+                current,
+                new,
+                Ordering::AcqRel,
+                Ordering::Acquire,
+            ) {
+                Ok(_) => break,
+                Err(next_current) => current = next_current,
+            }
+        }
+
+        // We have just marked the task as scheduled, so enqueue it.
+        let executor = &*self.executor.get();
+        executor.enqueue(self as *const TaskHeader as *mut TaskHeader);
+    }
 }
 
 // repr(C) is needed to guarantee that header is located at offset 0
@@ -35,59 +65,9 @@ pub(crate) struct TaskHeader {
 #[repr(C)]
 pub struct Task<F: Future + 'static> {
     header: TaskHeader,
-    future: UninitCell<F>, // Valid if STATE_RUNNING
+    future: UninitCell<F>, // Valid if STATE_SPAWNED
 }
 
-#[derive(Copy, Clone, Debug)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
-pub enum SpawnError {
-    Busy,
-}
-
-//=============
-// Waker
-
-static WAKER_VTABLE: RawWakerVTable =
-    RawWakerVTable::new(waker_clone, waker_wake, waker_wake, waker_drop);
-
-unsafe fn waker_clone(p: *const ()) -> RawWaker {
-    RawWaker::new(p, &WAKER_VTABLE)
-}
-
-unsafe fn waker_wake(p: *const ()) {
-    let header = &*(p as *const TaskHeader);
-
-    let mut current = header.state.load(Ordering::Acquire);
-    loop {
-        // If already scheduled, or if not started,
-        if (current & STATE_RUN_QUEUED != 0) || (current & STATE_RUNNING == 0) {
-            return;
-        }
-
-        // Mark it as scheduled
-        let new = current | STATE_RUN_QUEUED;
-
-        match header
-            .state
-            .compare_exchange_weak(current, new, Ordering::AcqRel, Ordering::Acquire)
-        {
-            Ok(_) => break,
-            Err(next_current) => current = next_current,
-        }
-    }
-
-    // We have just marked the task as scheduled, so enqueue it.
-    let executor = &*header.executor.get();
-    executor.enqueue(p as *mut TaskHeader);
-}
-
-unsafe fn waker_drop(_: *const ()) {
-    // nop
-}
-
-//=============
-// Task
-
 impl<F: Future + 'static> Task<F> {
     pub const fn new() -> Self {
         Self {
@@ -103,7 +83,7 @@ impl<F: Future + 'static> Task<F> {
 
     pub unsafe fn spawn(pool: &'static [Self], future: impl FnOnce() -> F) -> SpawnToken {
         for task in pool {
-            let state = STATE_RUNNING | STATE_RUN_QUEUED;
+            let state = STATE_SPAWNED | STATE_RUN_QUEUED;
             if task
                 .header
                 .state
@@ -129,14 +109,14 @@ impl<F: Future + 'static> Task<F> {
         let this = &*(p as *const Task<F>);
 
         let future = Pin::new_unchecked(this.future.as_mut());
-        let waker = Waker::from_raw(RawWaker::new(p as _, &WAKER_VTABLE));
+        let waker = waker::from_task(p);
         let mut cx = Context::from_waker(&waker);
         match future.poll(&mut cx) {
             Poll::Ready(_) => {
                 this.future.drop_in_place();
                 this.header
                     .state
-                    .fetch_and(!STATE_RUNNING, Ordering::AcqRel);
+                    .fetch_and(!STATE_SPAWNED, Ordering::AcqRel);
             }
             Poll::Pending => {}
         }
@@ -145,9 +125,6 @@ impl<F: Future + 'static> Task<F> {
 
 unsafe impl<F: Future + 'static> Sync for Task<F> {}
 
-//=============
-// Spawn token
-
 #[must_use = "Calling a task function does nothing on its own. You must pass the returned SpawnToken to Executor::spawn()"]
 pub struct SpawnToken {
     header: Option<NonNull<TaskHeader>>,
@@ -160,8 +137,11 @@ impl Drop for SpawnToken {
     }
 }
 
-//=============
-// Executor
+#[derive(Copy, Clone, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum SpawnError {
+    Busy,
+}
 
 pub struct Executor {
     run_queue: RunQueue,
@@ -207,7 +187,7 @@ impl Executor {
                 let header = &*p;
 
                 let state = header.state.fetch_and(!STATE_RUN_QUEUED, Ordering::AcqRel);
-                if state & STATE_RUNNING == 0 {
+                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.

embassy/src/executor/waker.rs

@@ -0,0 +1,22 @@
+use core::task::{RawWaker, RawWakerVTable, Waker};
+
+use super::TaskHeader;
+
+static VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake, drop);
+
+unsafe fn clone(p: *const ()) -> RawWaker {
+    RawWaker::new(p, &VTABLE)
+}
+
+unsafe fn wake(p: *const ()) {
+    let header = &*(p as *const TaskHeader);
+    header.enqueue();
+}
+
+unsafe fn drop(_: *const ()) {
+    // nop
+}
+
+pub(crate) unsafe fn from_task(p: *mut TaskHeader) -> Waker {
+    Waker::from_raw(RawWaker::new(p as _, &VTABLE))
+}