forked from M-Labs/zynq-rs
libasync: pin tasks to memory
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965a00801e
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@ -34,8 +34,13 @@ static VTABLE: RawWakerVTable = {
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///
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///
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/// This is a singleton
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/// This is a singleton
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pub struct Executor {
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pub struct Executor {
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// Entered block_on() already?
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in_block_on: RefCell<bool>,
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in_block_on: RefCell<bool>,
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tasks: RefCell<Deque<Task>>,
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/// Tasks reside on the heap, so that we just queue pointers. They
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/// must also be pinned in memory because our RawWaker is a pointer
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/// to their `ready` field.
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tasks: RefCell<Deque<Pin<Box<Task>>>>,
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}
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}
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impl Executor {
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impl Executor {
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@ -97,17 +102,14 @@ impl Executor {
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let mut cx = Context::from_waker(&waker);
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let mut cx = Context::from_waker(&waker);
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// this points into a `static` memory so it's already pinned
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// this points into a `static` memory so it's already pinned
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// println!("run task");
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// println!("run task");
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let ready = unsafe {
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let ready = task.f.as_mut().poll(&mut cx).is_ready();
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Pin::new_unchecked(&mut *task.f)
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if ready {
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.poll(&mut cx)
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// Task is finished, do not requeue
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.is_ready()
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continue;
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};
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// println!("ran task, ready={:?}", r);
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if !ready {
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// Task is not finished, requeue
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self.tasks.borrow_mut().push_back(task);
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}
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}
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}
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}
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// Requeue
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self.tasks.borrow_mut().push_back(task);
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}
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}
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// // try to sleep; this will be a no-op if any of the previous tasks generated a SEV or an
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// // try to sleep; this will be a no-op if any of the previous tasks generated a SEV or an
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@ -118,26 +120,22 @@ impl Executor {
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val
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val
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}
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}
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// NOTE CAREFUL! this method can overlap with `block_on`
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// FIXME we want to use `Future<Output = !>` here but the never type (`!`) is unstable; so as a
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// workaround we'll "abort" if the task / future terminates (see `Task::new`)
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pub fn spawn(&self, f: impl Future + 'static) {
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pub fn spawn(&self, f: impl Future + 'static) {
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// NOTE(unsafe) only safe as long as `spawn` is never re-entered and this does not overlap
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let task = Box::pin(Task::new(f));
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// with operation `(A)` (see `Task::block_on`)
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self.tasks.borrow_mut().push_back(task);
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self.tasks.borrow_mut().push_back(Task::new(f));
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}
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}
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}
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}
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pub struct Task {
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pub struct Task {
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ready: AtomicBool,
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ready: AtomicBool,
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f: Box<dyn Future<Output = ()>>,
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f: Pin<Box<dyn Future<Output = ()>>>,
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}
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}
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impl Task {
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impl Task {
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fn new(f: impl Future + 'static) -> Self {
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fn new(f: impl Future + 'static) -> Self {
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Task {
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Task {
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ready: AtomicBool::new(true),
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ready: AtomicBool::new(true),
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f: Box::new(async { f.await; }),
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f: Box::pin(async { f.await; }),
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}
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}
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}
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}
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}
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}
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@ -17,10 +17,7 @@ pub fn block_on<T>(f: impl Future<Output = T>) -> T {
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/// Spawns a task onto the executor
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/// Spawns a task onto the executor
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///
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///
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/// The spawned task will not make any progress until `block_on` is called.
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/// The spawned task will not make any progress until `block_on` is called.
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///
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pub fn spawn(f: impl Future + 'static) {
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/// The future `f` must never terminate. The program will *abort* if `f` (the async code) returns.
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/// The right signature here would be `f: impl Future<Output = !>` but that requires nightly
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pub fn spawn<T>(f: impl Future<Output = T> + 'static) {
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executor::current().spawn(f)
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executor::current().spawn(f)
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}
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}
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