zephyr: Remove work-queue executor

The work-queue-based executor was an attempt to implement a Rust
executor that worked with Zephyr work queues.  Although it was possible
to make something that kind of worked, and did have the advantage of
being able to use a few Zephyr primitives, it suffers from several
problems:

- It isn't very efficient, basically combining the overhead of async
  scheduling, triggered work, and the Zephyr thread scheduler.
- It plays poorly with any other use of async.  Since it is useful to be
  able to use external crates for async utilities, this normally just
  results in undefined-behavior.

Now that we have another executor (built from Embassy), this code is
also mostly unneeded.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

zephyr/src/kio.rs

@@ -80,8 +80,6 @@ pub mod align;
 pub mod device;
 pub mod embassy;
 pub mod error;
-#[cfg(CONFIG_RUST_ALLOC)]
-pub mod kio;
 pub mod logging;
 pub mod object;
 #[cfg(CONFIG_RUST_ALLOC)]

zephyr/src/kio/sync.rs

@@ -48,13 +48,15 @@ impl<T> PinWeak<T> {
     /// This would be easier to use if it could be added to Arc.
     pub fn downgrade(this: Pin<Arc<T>>) -> Self {
         // SAFETY: we will never return anything other than a Pin<Arc<T>>.
-        Self(Arc::downgrade(& unsafe { Pin::into_inner_unchecked(this) }))
+        Self(Arc::downgrade(&unsafe { Pin::into_inner_unchecked(this) }))
     }
 
     /// Upgrade back to a `Pin<Arc<T>>`.
     pub fn upgrade(&self) -> Option<Pin<Arc<T>>> {
         // SAFETY: The weak was only constructed from a `Pin<Arc<T>>`.
-        self.0.upgrade().map(|arc| unsafe { Pin::new_unchecked(arc) })
+        self.0
+            .upgrade()
+            .map(|arc| unsafe { Pin::new_unchecked(arc) })
     }
 }