erm.......

Cargo.toml

@@ -48,3 +48,4 @@ cfg-if = "1.0.0"
 [dev-dependencies]
 async-std = "1.13.0"
 tracing-test = "0.2.5"
+distaff = {path = "distaff"}

benches/join.rs

@@ -184,3 +184,36 @@ fn join_rayon(b: &mut Bencher) {
         assert_ne!(sum(&tree, tree.root().unwrap()), 0);
     });
 }
+
+#[bench]
+fn join_distaff(b: &mut Bencher) {
+    use distaff::*;
+    let pool = ThreadPool::new();
+    let tree = tree::Tree::new(TREE_SIZE, 1u32);
+
+    fn sum<'scope, 'env>(
+        tree: &tree::Tree<u32>,
+        node: usize,
+        scope: &'scope Scope<'scope, 'env>,
+    ) -> u32 {
+        let node = tree.get(node);
+        let (l, r) = scope.join(
+            |s| node.left.map(|node| sum(tree, node, s)).unwrap_or_default(),
+            |s| {
+                node.right
+                    .map(|node| sum(tree, node, s))
+                    .unwrap_or_default()
+            },
+        );
+
+        node.leaf + l + r
+    }
+
+    b.iter(move || {
+        pool.scope(|s| {
+            let sum = sum(&tree, tree.root().unwrap(), s);
+            // eprintln!("{sum}");
+            assert_ne!(sum, 0);
+        });
+    });
+}

distaff/Cargo.toml

@@ -13,4 +13,8 @@ tracing = "0.1.40"
 parking_lot_core = "0.9.10"
 crossbeam-utils = "0.8.21"
 
-async-task = "4.7.1"
+async-task = "4.7.1"
+
+[dev-dependencies]
+tracing-test = "0.2.5"
+futures = "0.3"

distaff/src/context.rs

@@ -8,11 +8,12 @@ use std::{
 
 use alloc::collections::BTreeMap;
 
+use async_task::Runnable;
 use crossbeam_utils::CachePadded;
 use parking_lot::{Condvar, Mutex};
 
 use crate::{
-    job::{Job, StackJob},
+    job::{HeapJob, Job, StackJob},
     latch::{LatchRef, MutexLatch, WakeLatch},
     workerthread::{HeartbeatThread, WorkerThread},
 };
@@ -50,10 +51,6 @@ impl Heartbeat {
     pub fn is_pending(&self) -> bool {
         self.heartbeat.load(Ordering::Relaxed) == Self::PENDING
     }
-
-    pub fn is_sleeping(&self) -> bool {
-        self.heartbeat.load(Ordering::Relaxed) == Self::SLEEPING
-    }
 }
 
 pub struct Context {
@@ -87,6 +84,7 @@ impl Shared {
         // this is unlikely, so make the function cold?
         // TODO: profile this
         if !self.injected_jobs.is_empty() {
+            // SAFETY: we checked that injected_jobs is not empty
             unsafe { return Some(self.pop_injected_job()) };
         } else {
             self.jobs.pop_first().map(|(_, job)| job)
@@ -105,7 +103,7 @@ impl Shared {
 
 impl Context {
     #[inline]
-    pub fn shared(&self) -> parking_lot::MutexGuard<'_, Shared> {
+    pub(crate) fn shared(&self) -> parking_lot::MutexGuard<'_, Shared> {
         self.shared.lock()
     }
 
@@ -159,6 +157,17 @@ impl Context {
         this
     }
 
+    pub fn set_should_exit(&self) {
+        let mut shared = self.shared.lock();
+        shared.should_exit = true;
+        for (_, heartbeat) in shared.heartbeats.iter() {
+            if let Some(heartbeat) = heartbeat.upgrade() {
+                heartbeat.latch.set();
+            }
+        }
+        self.shared_job.notify_all();
+    }
+
     pub fn new() -> Arc<Self> {
         Self::new_with_threads(crate::util::available_parallelism())
     }
@@ -270,6 +279,66 @@ impl Context {
     }
 }
 
+impl Context {
+    pub fn spawn<F>(self: &Arc<Self>, f: F)
+    where
+        F: FnOnce() + Send + 'static,
+    {
+        let job = Box::new(HeapJob::new(f)).into_boxed_job();
+        tracing::trace!("Context::spawn: spawning job: {:?}", job);
+        unsafe {
+            (&*job).set_pending();
+            self.inject_job(NonNull::new_unchecked(job));
+        }
+    }
+
+    pub fn spawn_future<T, F>(self: &Arc<Self>, future: F) -> async_task::Task<T>
+    where
+        F: Future<Output = T> + Send + 'static,
+        T: Send + 'static,
+    {
+        let schedule = move |runnable: Runnable| {
+            #[align(8)]
+            unsafe fn harness<T>(this: *const (), job: *const Job<T>) {
+                unsafe {
+                    let runnable =
+                        Runnable::<()>::from_raw(NonNull::new_unchecked(this.cast_mut()));
+                    runnable.run();
+
+                    // SAFETY: job was turned into raw
+                    drop(Box::from_raw(job.cast_mut()));
+                }
+            }
+
+            let job = Box::new(Job::<T>::new(harness::<T>, runnable.into_raw()));
+
+            // casting into Job<()> here
+            unsafe {
+                job.set_pending();
+                self.inject_job(NonNull::new_unchecked(Box::into_raw(job) as *mut Job<()>));
+            }
+        };
+
+        let (runnable, task) = unsafe { async_task::spawn_unchecked(future, schedule) };
+
+        runnable.schedule();
+
+        task
+    }
+
+    #[allow(dead_code)]
+    fn spawn_async<T, Fut, Fn>(self: &Arc<Self>, f: Fn) -> async_task::Task<T>
+    where
+        Fn: FnOnce() -> Fut + Send + 'static,
+        Fut: Future<Output = T> + Send + 'static,
+        T: Send + 'static,
+    {
+        let future = async move { f().await };
+
+        self.spawn_future(future)
+    }
+}
+
 pub fn run_in_worker<T, F>(f: F) -> T
 where
     T: Send,
@@ -277,3 +346,56 @@ where
 {
     Context::global_context().run_in_worker(f)
 }
+
+#[cfg(test)]
+mod tests {
+    use tracing_test::traced_test;
+
+    use super::*;
+
+    #[test]
+    fn run_in_worker_test() {
+        let ctx = Context::global_context().clone();
+        let result = ctx.run_in_worker(|_| 42);
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn spawn_future_test() {
+        let ctx = Context::global_context().clone();
+        let task = ctx.spawn_future(async { 42 });
+
+        // Wait for the task to complete
+        let result = futures::executor::block_on(task);
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn spawn_async_test() {
+        let ctx = Context::global_context().clone();
+        let task = ctx.spawn_async(|| async { 42 });
+
+        // Wait for the task to complete
+        let result = futures::executor::block_on(task);
+        assert_eq!(result, 42);
+    }
+
+    #[test]
+    fn spawn_test() {
+        let ctx = Context::global_context().clone();
+        let counter = Arc::new(AtomicU8::new(0));
+        let barrier = Arc::new(std::sync::Barrier::new(2));
+
+        ctx.spawn({
+            let counter = counter.clone();
+            let barrier = barrier.clone();
+            move || {
+                counter.fetch_add(1, Ordering::SeqCst);
+                barrier.wait();
+            }
+        });
+
+        barrier.wait();
+        assert_eq!(counter.load(Ordering::SeqCst), 1);
+    }
+}

distaff/src/job.rs

@@ -40,6 +40,59 @@ impl JobState {
 }
 
 pub use joblist::JobList;
+pub use jobvec::JobVec;
+
+// replacement for `JobList` that uses a VecDeque instead of a linked list.
+mod jobvec {
+    use std::ptr::NonNull;
+
+    use super::Job;
+    use alloc::collections::VecDeque;
+
+    #[derive(Debug)]
+    pub struct JobVec {
+        jobs: VecDeque<NonNull<Job>>,
+    }
+
+    impl JobVec {
+        pub fn new() -> Self {
+            Self {
+                jobs: VecDeque::new(),
+            }
+        }
+
+        pub fn remove(&mut self, job: &Job) {
+            // SAFETY: job is guaranteed to be valid and non-null
+            let job_ptr = unsafe { NonNull::new_unchecked(job as *const Job as _) };
+            self.jobs.retain(|j| *j != job_ptr);
+        }
+
+        pub fn push_front<T>(&mut self, job: *const Job<T>) {
+            let job_ptr = unsafe { NonNull::new_unchecked(job as _) };
+            self.jobs.push_front(job_ptr);
+        }
+        pub fn push_back<T>(&mut self, job: *const Job<T>) {
+            let job_ptr = unsafe { NonNull::new_unchecked(job as _) };
+            self.jobs.push_back(job_ptr);
+        }
+
+        pub fn pop_front(&mut self) -> Option<NonNull<Job>> {
+            self.jobs.pop_front()
+        }
+
+        pub fn pop_back(&mut self) -> Option<NonNull<Job>> {
+            self.jobs.pop_back()
+        }
+
+        pub fn is_empty(&self) -> bool {
+            self.jobs.is_empty()
+        }
+
+        pub fn len(&self) -> usize {
+            self.jobs.len()
+        }
+    }
+}
 
 mod joblist {
     use core::{fmt::Debug, ptr::NonNull};
@@ -87,6 +140,12 @@ mod joblist {
             self.tail
         }
 
+        pub fn remove(&mut self, job: &Job) {
+            job.unlink();
+
+            self.job_count -= 1;
+        }
+
         /// `job` must be valid until it is removed from the list.
         pub unsafe fn push_front<T>(&mut self, job: *const Job<T>) {
             self.job_count += 1;
@@ -124,8 +183,6 @@ mod joblist {
         }
 
         pub fn pop_front(&mut self) -> Option<NonNull<Job>> {
-            self.job_count -= 1;
-
             let headlink = unsafe { self.head.as_ref().link_mut() };
 
             // SAFETY: headlink.next is guaranteed to be Some.
@@ -139,12 +196,13 @@ mod joblist {
             headlink.next = Some(next);
             next_link.prev = Some(self.head);
 
+            // decrement job count after having potentially short-circuited
+            self.job_count -= 1;
+
             Some(job)
         }
 
         pub fn pop_back(&mut self) -> Option<NonNull<Job>> {
-            self.job_count -= 1;
-
             let taillink = unsafe { self.tail.as_ref().link_mut() };
 
             // SAFETY: taillink.prev is guaranteed to be Some.
@@ -158,6 +216,9 @@ mod joblist {
             taillink.prev = Some(prev);
             prev_link.next = Some(self.tail);
 
+            // decrement job count after having potentially short-circuited
+            self.job_count -= 1;
+
             Some(job)
         }
 
@@ -266,8 +327,6 @@ impl<T> Clone for Link<T> {
 // `Link` is invariant over `T`
 impl<T> Copy for Link<T> {}
 
-struct Thread;
-
 union ValueOrThis<T> {
     uninit: (),
     value: ManuallyDrop<SmallBox<T>>,
@@ -385,7 +444,8 @@ impl<T> Job<T> {
     }
 
     /// assumes job is in a `JobList`
-    pub unsafe fn unlink(&self) {
+    pub fn unlink(&self) {
+        // SAFETY: if the job isn't linked, these will operate on a dummy value.
         unsafe {
             let mut dummy = None;
             let Link { prev, next } = *self.link_mut();
@@ -590,6 +650,7 @@ mod stackjob {
 
                 let result = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| f()));
 
+                tracing::trace!("job completed: {:?}", job);
                 let job = unsafe { &*job.cast::<Job<T>>() };
                 job.complete(result);
 
@@ -664,3 +725,248 @@ mod heapjob {
 
 pub use heapjob::HeapJob;
 pub use stackjob::StackJob;
+
+#[cfg(test)]
+mod tests {
+    use crate::latch::{AtomicLatch, LatchRef};
+
+    use super::*;
+
+    #[test]
+    fn job_lifecycle() {
+        let latch = AtomicLatch::new();
+        let stack = StackJob::new(|| 3 + 4, LatchRef::new(&latch));
+
+        let job = stack.as_job::<i32>();
+
+        assert_eq!(job.state(), JobState::Empty as u8);
+
+        job.set_pending();
+        assert_eq!(job.state(), JobState::Pending as u8);
+
+        // execute the job
+        Job::<()>::execute(unsafe { NonNull::new_unchecked(&job as *const Job as _) });
+
+        // wait for the job to finish
+        let result = unsafe { job.transmute_ref::<i32>().wait() };
+        assert_eq!(result.into_result(), 7);
+    }
+
+    #[test]
+    fn job_lifecycle_panic() {
+        let latch = AtomicLatch::new();
+        let stack = StackJob::new(|| panic!("test panic"), LatchRef::new(&latch));
+
+        let job = stack.as_job::<i32>();
+
+        assert_eq!(job.state(), JobState::Empty as u8);
+
+        job.set_pending();
+        assert_eq!(job.state(), JobState::Pending as u8);
+
+        // execute the job
+        Job::<()>::execute(unsafe { NonNull::new_unchecked(&job as *const Job as _) });
+
+        // wait for the job to finish
+        let result = unsafe { job.transmute_ref::<i32>().wait() };
+        assert!(result.into_inner().is_err());
+    }
+
+    #[test]
+    fn joblist_popback() {
+        let mut list = JobList::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        unsafe {
+            list.push_back(job1);
+            list.push_back(job2);
+        }
+
+        assert_eq!(list.len(), 2);
+
+        let popped_job = list.pop_back().unwrap();
+        assert_eq!(popped_job.as_ptr(), job2 as _);
+
+        let popped_job = list.pop_back().unwrap();
+        assert_eq!(popped_job.as_ptr(), job1 as _);
+
+        assert!(list.is_empty());
+    }
+
+    #[test]
+    fn joblist_popfront() {
+        let mut list = JobList::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        unsafe {
+            list.push_front(job1);
+            list.push_front(job2);
+        }
+
+        assert_eq!(list.len(), 2);
+
+        let popped_job = list.pop_front().unwrap();
+        assert_eq!(popped_job.as_ptr(), job2 as _);
+
+        let popped_job = list.pop_front().unwrap();
+        assert_eq!(popped_job.as_ptr(), job1 as _);
+
+        assert!(list.is_empty());
+    }
+
+    #[test]
+    fn joblist_unlink_middle() {
+        let mut list = JobList::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job3 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        unsafe {
+            list.push_back(job1);
+            list.push_back(job2);
+            list.push_back(job3);
+        }
+
+        assert_eq!(list.len(), 3);
+
+        // Unlink the middle job (job2)
+        unsafe {
+            (&*job2).unlink();
+        }
+
+        // Check that job1 and job3 are still in the list
+        let popped_job1 = list.pop_front().unwrap();
+        assert_eq!(popped_job1.as_ptr(), job1 as _);
+
+        let popped_job3 = list.pop_front().unwrap();
+        assert_eq!(popped_job3.as_ptr(), job3 as _);
+    }
+
+    #[test]
+    fn joblist_unlink_head() {
+        let mut list = JobList::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        unsafe {
+            list.push_back(job1);
+            list.push_back(job2);
+        }
+
+        assert_eq!(list.len(), 2);
+
+        unsafe {
+            (&*job1).unlink();
+        }
+
+        // Check that job2 is still in the list
+        let popped_job2 = list.pop_front().unwrap();
+        assert_eq!(popped_job2.as_ptr(), job2 as _);
+    }
+
+    #[test]
+    fn joblist_unlink_tail() {
+        let mut list = JobList::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        unsafe {
+            list.push_back(job1);
+            list.push_back(job2);
+        }
+
+        assert_eq!(list.len(), 2);
+
+        unsafe {
+            (&*job2).unlink();
+        }
+
+        // Check that job1 is still in the list
+        let popped_job1 = list.pop_front().unwrap();
+        assert_eq!(popped_job1.as_ptr(), job1 as _);
+    }
+
+    #[test]
+    fn joblist_unlink_single() {
+        let mut list = JobList::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        unsafe {
+            list.push_back(job1);
+        }
+
+        assert_eq!(list.len(), 1);
+
+        unsafe {
+            (&*job1).unlink();
+        }
+
+        // Check that popping from an empty list returns None
+        assert!(list.pop_front().is_none());
+    }
+
+    #[test]
+    fn joblist_pop_empty() {
+        let mut list = JobList::new();
+
+        // Popping from an empty list should return None
+        assert!(list.pop_front().is_none());
+        assert!(list.pop_back().is_none());
+    }
+
+    #[test]
+    fn jobvec_push_front() {
+        let mut vec = JobVec::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        vec.push_front(job1);
+        vec.push_front(job2);
+
+        assert_eq!(vec.len(), 2);
+
+        let popped_job = vec.pop_front().unwrap();
+        assert_eq!(popped_job.as_ptr(), job2 as _);
+        let popped_job = vec.pop_front().unwrap();
+        assert_eq!(popped_job.as_ptr(), job1 as _);
+        assert!(vec.is_empty());
+    }
+
+    #[test]
+    fn jobvec_push_back() {
+        let mut vec = JobVec::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        vec.push_back(job1);
+        vec.push_back(job2);
+
+        assert_eq!(vec.len(), 2);
+
+        let popped_job = vec.pop_back().unwrap();
+        assert_eq!(popped_job.as_ptr(), job2 as _);
+        let popped_job = vec.pop_back().unwrap();
+        assert_eq!(popped_job.as_ptr(), job1 as _);
+        assert!(vec.is_empty());
+    }
+
+    #[test]
+    fn jobvec_push_front_pop_back() {
+        let mut vec = JobVec::new();
+        let job1 = Box::into_raw(Box::new(Job::<i32>::empty()));
+        let job2 = Box::into_raw(Box::new(Job::<i32>::empty()));
+
+        vec.push_front(job1);
+        vec.push_front(job2);
+
+        assert_eq!(vec.len(), 2);
+
+        let popped_job = vec.pop_back().unwrap();
+        assert_eq!(popped_job.as_ptr(), job1 as _);
+        let popped_job = vec.pop_back().unwrap();
+        assert_eq!(popped_job.as_ptr(), job2 as _);
+        assert!(vec.is_empty());
+    }
+}

distaff/src/join.rs

@@ -1,6 +1,7 @@
-use std::hint::cold_path;
+use std::{hint::cold_path, sync::Arc};
 
 use crate::{
+    context::Context,
     job::{JobState, StackJob},
     latch::{AsCoreLatch, LatchRef, WakeLatch},
     workerthread::WorkerThread,
@@ -69,7 +70,6 @@ impl WorkerThread {
                 // WorkerThread::current_ref()
                 //     .expect("stackjob is run in workerthread.")
                 //     .tick();
-
                 a()
             },
             LatchRef::new(&latch),
@@ -82,6 +82,7 @@ impl WorkerThread {
             Ok(val) => val,
             Err(payload) => {
                 cold_path();
+                tracing::debug!("join_heartbeat: b panicked, waiting for a to finish");
                 // if b panicked, we need to wait for a to finish
                 self.wait_until_latch(&latch);
                 resume_unwind(payload);
@@ -89,8 +90,11 @@ impl WorkerThread {
         };
 
         let ra = if job.state() == JobState::Empty as u8 {
+            // remove job from the queue, so it doesn't get run again.
+            // job.unlink();
+            //SAFETY: we are in a worker thread, so we can safely access the queue.
             unsafe {
-                job.unlink();
+                self.queue.as_mut_unchecked().remove(&job);
             }
 
             // a is allowed to panic here, because we already finished b.
@@ -108,3 +112,41 @@ impl WorkerThread {
         (ra, rb)
     }
 }
+
+impl Context {
+    #[inline]
+    pub fn join<A, B, RA, RB>(self: &Arc<Self>, a: A, b: B) -> (RA, RB)
+    where
+        RA: Send,
+        RB: Send,
+        A: FnOnce() -> RA + Send,
+        B: FnOnce() -> RB + Send,
+    {
+        // SAFETY: join_heartbeat_every is safe to call from a worker thread.
+        self.run_in_worker(move |worker| worker.join_heartbeat_every::<_, _, _, _, 64>(a, b))
+    }
+}
+
+/// run two closures potentially in parallel, in the global threadpool.
+#[allow(dead_code)]
+pub fn join<A, B, RA, RB>(a: A, b: B) -> (RA, RB)
+where
+    RA: Send,
+    RB: Send,
+    A: FnOnce() -> RA + Send,
+    B: FnOnce() -> RB + Send,
+{
+    join_in(Context::global_context().clone(), a, b)
+}
+
+/// run two closures potentially in parallel, in the global threadpool.
+#[allow(dead_code)]
+fn join_in<A, B, RA, RB>(context: Arc<Context>, a: A, b: B) -> (RA, RB)
+where
+    RA: Send,
+    RB: Send,
+    A: FnOnce() -> RA + Send,
+    B: FnOnce() -> RB + Send,
+{
+    context.join(a, b)
+}

distaff/src/latch.rs

@@ -37,6 +37,13 @@ impl AtomicLatch {
             inner: AtomicU8::new(Self::UNSET),
         }
     }
+
+    pub const fn new_set() -> Self {
+        Self {
+            inner: AtomicU8::new(Self::SET),
+        }
+    }
+
     #[inline]
     pub fn reset(&self) {
         self.inner.store(Self::UNSET, Ordering::Release);
@@ -46,6 +53,10 @@ impl AtomicLatch {
         self.inner.load(Ordering::Acquire)
     }
 
+    pub fn set_sleeping(&self) {
+        self.inner.store(Self::SLEEPING, Ordering::Release);
+    }
+
     /// returns true if the latch was previously sleeping.
     #[inline]
     pub unsafe fn set(this: *const Self) -> bool {
@@ -244,7 +255,7 @@ impl<L: Latch> Latch for CountLatch<L> {
 impl<L: Latch + Probe> Probe for CountLatch<L> {
     #[inline]
     fn probe(&self) -> bool {
-        self.inner.probe()
+        self.count.load(Ordering::Relaxed) == 0
     }
 }
 
@@ -365,3 +376,168 @@ impl AsCoreLatch for WakeLatch {
         &self.inner
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::sync::Barrier;
+
+    use tracing::Instrument;
+    use tracing_test::traced_test;
+
+    use super::*;
+
+    #[test]
+    fn test_atomic_latch() {
+        let latch = AtomicLatch::new();
+        assert_eq!(latch.get(), AtomicLatch::UNSET);
+        unsafe {
+            assert!(!latch.probe());
+            AtomicLatch::set_raw(&latch);
+        }
+        assert_eq!(latch.get(), AtomicLatch::SET);
+        assert!(latch.probe());
+        latch.reset();
+        assert_eq!(latch.get(), AtomicLatch::UNSET);
+    }
+
+    #[test]
+    fn core_latch_sleep() {
+        let latch = AtomicLatch::new();
+        assert_eq!(latch.get(), AtomicLatch::UNSET);
+        latch.set_sleeping();
+        assert_eq!(latch.get(), AtomicLatch::SLEEPING);
+        unsafe {
+            assert!(!latch.probe());
+            assert!(AtomicLatch::set(&latch));
+        }
+        assert_eq!(latch.get(), AtomicLatch::SET);
+        assert!(latch.probe());
+        latch.reset();
+        assert_eq!(latch.get(), AtomicLatch::UNSET);
+    }
+
+    #[test]
+    fn nop_latch() {
+        assert!(
+            core::mem::size_of::<NopLatch>() == 0,
+            "NopLatch should be zero-sized"
+        );
+    }
+
+    #[test]
+    fn thread_wake_latch() {
+        let latch = Arc::new(ThreadWakeLatch::new());
+        let main = Arc::new(ThreadWakeLatch::new());
+
+        let handle = std::thread::spawn({
+            let latch = latch.clone();
+            let main = main.clone();
+            move || unsafe {
+                Latch::set_raw(&*main);
+                latch.wait();
+            }
+        });
+
+        unsafe {
+            main.wait();
+            Latch::set_raw(&*latch);
+        }
+
+        handle.join().expect("Thread should join successfully");
+        assert!(
+            !latch.probe() && !main.probe(),
+            "Latch should be set after waiting thread wakes up"
+        );
+    }
+
+    #[test]
+    fn count_latch() {
+        let latch = CountLatch::new(AtomicLatch::new());
+        assert_eq!(latch.count(), 0);
+        latch.increment();
+        assert_eq!(latch.count(), 1);
+        assert!(!latch.probe());
+        latch.increment();
+        assert_eq!(latch.count(), 2);
+        assert!(!latch.probe());
+
+        unsafe {
+            Latch::set_raw(&latch);
+        }
+        assert!(!latch.probe());
+        assert_eq!(latch.count(), 1);
+
+        unsafe {
+            Latch::set_raw(&latch);
+        }
+        assert!(latch.probe());
+        assert_eq!(latch.count(), 0);
+    }
+
+    #[test]
+    fn mutex_latch() {
+        let latch = Arc::new(MutexLatch::new());
+        assert!(!latch.probe());
+        latch.set();
+        assert!(latch.probe());
+        latch.reset();
+        assert!(!latch.probe());
+
+        // Test wait functionality
+        let latch_clone = latch.clone();
+        let handle = std::thread::spawn(move || {
+            latch_clone.wait();
+        });
+
+        // Give the thread time to block
+        std::thread::sleep(std::time::Duration::from_millis(100));
+        assert!(!latch.probe());
+
+        latch.set();
+        assert!(latch.probe());
+        handle.join().expect("Thread should join successfully");
+    }
+
+    #[test]
+    fn wake_latch() {
+        let context = Context::new_with_threads(1);
+        let count = Arc::new(AtomicUsize::new(0));
+        let barrier = Arc::new(Barrier::new(2));
+
+        tracing::info!("running scope in worker thread");
+        let latch = context.run_in_worker(|worker| {
+            tracing::info!("worker thread started: {:?}", worker.index);
+            let latch = WakeLatch::new(worker.context.clone(), worker.index);
+            worker.context.spawn({
+                let heartbeat = worker.heartbeat.clone();
+                let barrier = barrier.clone();
+                let count = count.clone();
+                // set sleeping outside of the closure so we don't have to deal with lifetimes
+                latch.as_core_latch().set_sleeping();
+                move || {
+                    tracing::info!("sleeping workerthread");
+                    heartbeat.latch.wait_and_reset();
+                    tracing::info!("woken up workerthread");
+                    count.fetch_add(1, Ordering::SeqCst);
+                    tracing::info!("waiting on barrier");
+                    barrier.wait();
+                }
+            });
+
+            latch
+        });
+
+        tracing::info!("setting latch in main thread");
+        unsafe {
+            Latch::set_raw(&latch);
+        }
+
+        tracing::info!("main thread set latch, waiting for worker thread to wake up");
+        barrier.wait();
+        assert_eq!(
+            count.load(Ordering::SeqCst),
+            1,
+            "Latch should have woken the worker thread"
+        );
+    }
+}

distaff/src/lib.rs

@@ -20,3 +20,9 @@ mod scope;
 mod threadpool;
 pub mod util;
 mod workerthread;
+
+pub use context::run_in_worker;
+pub use join::join;
+pub use scope::{Scope, scope};
+pub use threadpool::ThreadPool;
+pub use workerthread::WorkerThread;

distaff/src/scope.rs

@@ -11,14 +11,14 @@ use std::{
 use async_task::Runnable;
 
 use crate::{
-    context::{Context, run_in_worker},
+    context::Context,
     job::{HeapJob, Job},
     latch::{AsCoreLatch, CountLatch, WakeLatch},
     util::{DropGuard, SendPtr},
     workerthread::WorkerThread,
 };
 
-pub struct Scope<'scope> {
+pub struct Scope<'scope, 'env: 'scope> {
     // latch to wait on before the scope finishes
     job_counter: CountLatch<WakeLatch>,
     // local threadpool
@@ -26,55 +26,44 @@ pub struct Scope<'scope> {
     // panic error
     panic: AtomicPtr<Box<dyn Any + Send + 'static>>,
     // variant lifetime
-    _pd: PhantomData<fn(&'scope ())>,
+    _scope: PhantomData<&'scope mut &'scope ()>,
+    _env: PhantomData<&'env mut &'env ()>,
 }
 
-pub fn scope<'scope, F, R>(f: F) -> R
+pub fn scope<'env, F, R>(f: F) -> R
 where
-    F: FnOnce(&Scope<'scope>) -> R + Send,
+    F: for<'scope> FnOnce(&'scope Scope<'scope, 'env>) -> R + Send,
     R: Send,
 {
-    Scope::<'scope>::scope(f)
+    scope_with_context(Context::global_context(), f)
 }
 
-impl<'scope> Scope<'scope> {
+pub fn scope_with_context<'env, F, R>(context: &Arc<Context>, f: F) -> R
+where
+    F: for<'scope> FnOnce(&'scope Scope<'scope, 'env>) -> R + Send,
+    R: Send,
+{
+    context.run_in_worker(|worker| {
+        // SAFETY: we call complete() after creating this scope, which
+        // ensures that any jobs spawned from the scope exit before the
+        // scope closes.
+        let this = unsafe { Scope::from_context(context.clone()) };
+        this.complete(worker, || f(&this))
+    })
+}
+
+impl<'scope, 'env> Scope<'scope, 'env> {
     fn wait_for_jobs(&self, worker: &WorkerThread) {
-        tracing::trace!("waiting for {} jobs to finish.", self.job_counter.count());
-        tracing::trace!("thread id: {:?}, jobs: {:?}", worker.index, unsafe {
-            worker.queue.as_ref_unchecked()
-        });
+        if self.job_counter.count() > 0 {
+            tracing::trace!("waiting for {} jobs to finish.", self.job_counter.count());
+            tracing::trace!("thread id: {:?}, jobs: {:?}", worker.index, unsafe {
+                worker.queue.as_ref_unchecked()
+            });
 
-        // set worker index in the job counter
-        self.job_counter.inner().set_worker_index(worker.index);
-        worker.wait_until_latch(self.job_counter.as_core_latch());
-    }
-
-    pub fn scope<F, R>(f: F) -> R
-    where
-        F: FnOnce(&Self) -> R + Send,
-        R: Send,
-    {
-        run_in_worker(|worker| {
-            // SAFETY: we call complete() after creating this scope, which
-            // ensures that any jobs spawned from the scope exit before the
-            // scope closes.
-            let this = unsafe { Self::from_context(worker.context.clone()) };
-            this.complete(worker, || f(&this))
-        })
-    }
-
-    fn scope_with_context<F, R>(context: Arc<Context>, f: F) -> R
-    where
-        F: FnOnce(&Self) -> R + Send,
-        R: Send,
-    {
-        context.run_in_worker(|worker| {
-            // SAFETY: we call complete() after creating this scope, which
-            // ensures that any jobs spawned from the scope exit before the
-            // scope closes.
-            let this = unsafe { Self::from_context(context.clone()) };
-            this.complete(worker, || f(&this))
-        })
+            // set worker index in the job counter
+            self.job_counter.inner().set_worker_index(worker.index);
+            worker.wait_until_latch(self.job_counter.as_core_latch());
+        }
     }
 
     /// should be called from within a worker thread.
@@ -153,9 +142,9 @@ impl<'scope> Scope<'scope> {
         });
     }
 
-    pub fn spawn<F>(&self, f: F)
+    pub fn spawn<F>(&'scope self, f: F)
     where
-        F: FnOnce(&Scope<'scope>) + Send,
+        F: FnOnce(&'scope Self) + Send,
     {
         self.context.run_in_worker(|worker| {
             self.job_counter.increment();
@@ -176,70 +165,81 @@ impl<'scope> Scope<'scope> {
         });
     }
 
-    pub fn spawn_future<T, F>(&self, future: F) -> async_task::Task<T>
+    pub fn spawn_future<T, F>(&'scope self, future: F) -> async_task::Task<T>
     where
         F: Future<Output = T> + Send + 'scope,
         T: Send + 'scope,
     {
-        self.context.run_in_worker(|worker| {
-            self.job_counter.increment();
-
-            let this = SendPtr::new_const(&self.job_counter).unwrap();
-
-            let future = async move {
-                let _guard = DropGuard::new(move || unsafe {
-                    this.as_ref().decrement();
-                });
-                future.await
-            };
-
-            let schedule = move |runnable: Runnable| {
-                #[align(8)]
-                unsafe fn harness<T>(this: *const (), job: *const Job<T>) {
-                    unsafe {
-                        let runnable =
-                            Runnable::<()>::from_raw(NonNull::new_unchecked(this.cast_mut()));
-                        runnable.run();
-
-                        // SAFETY: job was turned into raw
-                        drop(Box::from_raw(job.cast_mut()));
-                    }
-                }
-
-                let job = Box::new(Job::<T>::new(harness::<T>, runnable.into_raw()));
-
-                // casting into Job<()> here
-                worker.push_front(Box::into_raw(job) as _);
-            };
-
-            let (runnable, task) = unsafe { async_task::spawn_unchecked(future, schedule) };
-
-            runnable.schedule();
-
-            task
-        })
+        self.spawn_async_internal(move |_| future)
     }
 
     #[allow(dead_code)]
-    fn spawn_async<'a, T, Fut, Fn>(&'a self, f: Fn) -> async_task::Task<T>
+    pub fn spawn_async<T, Fut, Fn>(&'scope self, f: Fn) -> async_task::Task<T>
     where
-        Fn: FnOnce(&Scope) -> Fut + Send + 'static,
-        Fut: Future<Output = T> + Send + 'static,
-        T: Send + 'static,
+        Fn: FnOnce(&'scope Self) -> Fut + Send + 'scope,
+        Fut: Future<Output = T> + Send + 'scope,
+        T: Send + 'scope,
     {
-        let this = SendPtr::new_const(self).unwrap();
-        let future = async move { f(unsafe { this.as_ref() }).await };
-
-        self.spawn_future(future)
+        self.spawn_async_internal(f)
     }
 
     #[inline]
-    pub fn join<A, B, RA, RB>(&self, a: A, b: B) -> (RA, RB)
+    fn spawn_async_internal<T, Fut, Fn>(&'scope self, f: Fn) -> async_task::Task<T>
+    where
+        Fn: FnOnce(&'scope Self) -> Fut + Send + 'scope,
+        Fut: Future<Output = T> + Send + 'scope,
+        T: Send + 'scope,
+    {
+        self.job_counter.increment();
+
+        let this = SendPtr::new_const(self).unwrap();
+        // let this = SendPtr::new_const(&self.job_counter).unwrap();
+
+        let future = async move {
+            // SAFETY: this is valid until we decrement the job counter.
+            unsafe {
+                let _guard = DropGuard::new(move || {
+                    this.as_unchecked_ref().job_counter.decrement();
+                });
+                f(this.as_ref()).await
+            }
+        };
+
+        let schedule = move |runnable: Runnable| {
+            #[align(8)]
+            unsafe fn harness(this: *const (), job: *const Job) {
+                unsafe {
+                    let runnable =
+                        Runnable::<()>::from_raw(NonNull::new_unchecked(this.cast_mut()));
+                    runnable.run();
+
+                    // SAFETY: job was turned into raw
+                    drop(Box::from_raw(job.cast_mut()));
+                }
+            }
+
+            let job = Box::new(Job::new(harness, runnable.into_raw()));
+
+            // casting into Job<()> here
+            WorkerThread::current_ref()
+                .expect("spawn_async_internal is run in workerthread.")
+                .push_front(Box::into_raw(job) as _);
+        };
+
+        let (runnable, task) = unsafe { async_task::spawn_unchecked(future, schedule) };
+
+        runnable.schedule();
+
+        task
+    }
+
+    #[inline]
+    pub fn join<A, B, RA, RB>(&'scope self, a: A, b: B) -> (RA, RB)
     where
         RA: Send,
         RB: Send,
-        A: FnOnce(&Self) -> RA + Send,
-        B: FnOnce(&Self) -> RB + Send,
+        A: FnOnce(&'scope Self) -> RA + Send,
+        B: FnOnce(&'scope Self) -> RB + Send,
     {
         let worker = WorkerThread::current_ref().expect("join is run in workerthread.");
         let this = SendPtr::new_const(self).unwrap();
@@ -261,7 +261,60 @@ impl<'scope> Scope<'scope> {
             context: ctx.clone(),
             job_counter: CountLatch::new(WakeLatch::new(ctx, 0)),
             panic: AtomicPtr::new(ptr::null_mut()),
-            _pd: PhantomData,
+            _scope: PhantomData,
+            _env: PhantomData,
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use std::sync::atomic::AtomicU8;
+
+    use tracing_test::traced_test;
+
+    use super::*;
+    use crate::ThreadPool;
+
+    #[test]
+    fn spawn() {
+        let pool = ThreadPool::new_with_threads(1);
+        let count = Arc::new(AtomicU8::new(0));
+
+        scope_with_context(&pool.context, |scope| {
+            scope.spawn(|_| {
+                count.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+            });
+        });
+
+        assert_eq!(count.load(std::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[test]
+    #[traced_test]
+    fn join() {
+        let pool = ThreadPool::new_with_threads(1);
+
+        let a = pool.scope(|scope| {
+            let (a, b) = scope.join(|_| 3 + 4, |_| 5 + 6);
+            a + b
+        });
+
+        assert_eq!(a, 18);
+    }
+
+    #[test]
+    fn spawn_future() {
+        let pool = ThreadPool::new_with_threads(1);
+        let mut x = 0;
+        pool.scope(|scope| {
+            let task = scope.spawn_async(|_| async {
+                x += 1;
+            });
+
+            task.detach();
+        });
+
+        assert_eq!(x, 1);
+    }
+}

distaff/src/threadpool.rs

@@ -1 +1,93 @@
+use std::sync::Arc;
 
+use crate::{Scope, context::Context, scope::scope_with_context};
+
+pub struct ThreadPool {
+    pub(crate) context: Arc<Context>,
+}
+
+impl Drop for ThreadPool {
+    fn drop(&mut self) {
+        // Ensure that the context is properly cleaned up when the thread pool is dropped.
+        self.context.set_should_exit();
+    }
+}
+
+impl ThreadPool {
+    pub fn new_with_threads(num_threads: usize) -> Self {
+        let context = Context::new_with_threads(num_threads);
+        Self { context }
+    }
+
+    /// Creates a new thread pool with a thread per hardware thread.
+    pub fn new() -> Self {
+        let context = Context::new();
+        Self { context }
+    }
+
+    pub fn scope<'env, F, R>(&self, f: F) -> R
+    where
+        F: for<'scope> FnOnce(&'scope Scope<'scope, 'env>) -> R + Send,
+        R: Send,
+    {
+        scope_with_context(&self.context, f)
+    }
+
+    pub fn spawn<F, R>(&self, f: F)
+    where
+        F: FnOnce() + Send + 'static,
+    {
+        self.context.spawn(f)
+    }
+
+    pub fn join<A, B, RA, RB>(&self, a: A, b: B) -> (RA, RB)
+    where
+        RA: Send,
+        RB: Send,
+        A: FnOnce() -> RA + Send,
+        B: FnOnce() -> RB + Send,
+    {
+        self.context.join(a, b)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn spawn_borrow() {
+        let pool = ThreadPool::new_with_threads(1);
+        let mut x = 0;
+        pool.scope(|scope| {
+            scope.spawn(|_| {
+                x += 1;
+            });
+        });
+        assert_eq!(x, 1);
+    }
+
+    #[test]
+    fn spawn_future() {
+        let pool = ThreadPool::new_with_threads(1);
+        let mut x = 0;
+        let task = pool.scope(|scope| {
+            let task = scope.spawn_async(|_| async {
+                x += 1;
+            });
+
+            task
+        });
+
+        futures::executor::block_on(task);
+        assert_eq!(x, 1);
+    }
+
+    #[test]
+    fn join() {
+        let pool = ThreadPool::new_with_threads(1);
+        let (a, b) = pool.join(|| 3 + 4, || 5 * 6);
+        assert_eq!(a, 7);
+        assert_eq!(b, 30);
+    }
+}

distaff/src/util.rs

@@ -93,6 +93,11 @@ impl<T> SendPtr<T> {
     pub const unsafe fn new_const_unchecked(ptr: *const T) -> Self {
         unsafe { Self::new_unchecked(ptr.cast_mut()) }
     }
+
+    pub unsafe fn as_unchecked_ref(&self) -> &T {
+        // SAFETY: `self.0` is a valid non-null pointer.
+        unsafe { self.0.as_ref() }
+    }
 }
 
 /// A tagged atomic pointer that can store a pointer and a tag `BITS` wide in the same space
@@ -402,3 +407,63 @@ pub fn available_parallelism() -> usize {
         .map(|n| n.get())
         .unwrap_or(1)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn tagged_ptr_exchange() {
+        let ptr = Box::into_raw(Box::new(42u32));
+        let tagged_ptr = TaggedAtomicPtr::<u32, 2>::new(ptr, 0b11);
+        assert_eq!(tagged_ptr.tag(Ordering::Relaxed), 0b11);
+        assert_eq!(tagged_ptr.ptr(Ordering::Relaxed).as_ptr(), ptr);
+
+        assert_eq!(
+            tagged_ptr
+                .compare_exchange_tag(0b11, 0b10, Ordering::Relaxed, Ordering::Relaxed)
+                .unwrap(),
+            0b11
+        );
+
+        assert_eq!(tagged_ptr.tag(Ordering::Relaxed), 0b10);
+        assert_eq!(tagged_ptr.ptr(Ordering::Relaxed).as_ptr(), ptr);
+
+        unsafe {
+            _ = Box::from_raw(ptr);
+        }
+    }
+
+    #[test]
+    fn value_inline() {
+        assert!(SmallBox::<u32>::is_inline(), "u32 should be inline");
+        assert!(SmallBox::<u8>::is_inline(), "u8 should be inline");
+        assert!(
+            SmallBox::<Box<u32>>::is_inline(),
+            "Box<u32> should be inline"
+        );
+        assert!(
+            SmallBox::<[u32; 2]>::is_inline(),
+            "[u32; 2] should be inline"
+        );
+        assert!(
+            !SmallBox::<[u32; 3]>::is_inline(),
+            "[u32; 3] should not be inline"
+        );
+        assert!(SmallBox::<usize>::is_inline(), "usize should be inline");
+
+        #[repr(C, align(16))]
+        struct LargeType(u8);
+        assert!(
+            !SmallBox::<LargeType>::is_inline(),
+            "LargeType should not be inline"
+        );
+
+        #[repr(C, align(4))]
+        struct SmallType(u8);
+        assert!(
+            SmallBox::<SmallType>::is_inline(),
+            "SmallType should be inline"
+        );
+    }
+}

distaff/src/workerthread.rs

@@ -6,11 +6,10 @@ use std::{
 };
 
 use crossbeam_utils::CachePadded;
-use parking_lot_core::SpinWait;
 
 use crate::{
     context::{Context, Heartbeat},
-    job::{Job, JobList, JobResult},
+    job::{Job, JobResult, JobVec as JobList},
     latch::{AsCoreLatch, CoreLatch, Probe},
     util::DropGuard,
 };
@@ -19,7 +18,7 @@ pub struct WorkerThread {
     pub(crate) context: Arc<Context>,
     pub(crate) index: usize,
     pub(crate) queue: UnsafeCell<JobList>,
-    heartbeat: Arc<CachePadded<Heartbeat>>,
+    pub(crate) heartbeat: Arc<CachePadded<Heartbeat>>,
     pub(crate) join_count: Cell<u8>,
 }
 
@@ -39,11 +38,6 @@ impl WorkerThread {
             join_count: Cell::new(0),
         }
     }
-
-    fn new() -> Self {
-        let context = Context::global_context().clone();
-        Self::new_in(context)
-    }
 }
 
 impl WorkerThread {
@@ -72,7 +66,7 @@ impl WorkerThread {
         let mut job = self.context.shared().pop_job();
         'outer: loop {
             let mut guard = loop {
-                if let Some(job) = job {
+                if let Some(job) = job.take() {
                     self.execute(job);
                 }
 
@@ -83,9 +77,11 @@ impl WorkerThread {
                     break 'outer;
                 }
 
+                // TODO: also check the local queue?
                 match guard.pop_job() {
-                    Some(job) => {
-                        tracing::trace!("worker: popping job: {:?}", job);
+                    Some(popped) => {
+                        tracing::trace!("worker: popping job: {:?}", popped);
+                        job = Some(popped);
                         // found job, continue inner loop
                         continue;
                     }
@@ -107,6 +103,7 @@ impl WorkerThread {
     #[inline(always)]
     fn tick(&self) {
         if self.heartbeat.is_pending() {
+            tracing::trace!("received heartbeat, thread id: {:?}", self.index);
             self.heartbeat_cold();
         }
     }
@@ -190,8 +187,11 @@ impl WorkerThread {
 
     unsafe fn drop_in_place(this: *mut Self) {
         unsafe {
-            this.drop_in_place();
-            drop(Box::from_raw(this));
+            // SAFETY: this is only called when the thread is exiting, so we can
+            // safely drop the thread. We use `drop_in_place` to prevent `Box`
+            // from creating a no-alias reference to the worker thread.
+            core::ptr::drop_in_place(this);
+            _ = Box::<core::mem::ManuallyDrop<Self>>::from_raw(this as _);
         }
     }
 }
@@ -258,11 +258,6 @@ impl WorkerThread {
         assert!(!latch.probe());
 
         'outer: while !latch.probe() {
-            // take a shared job, if it exists
-            if let Some(shared_job) = self.context.shared().jobs.remove(&self.index) {
-                self.execute(shared_job);
-            }
-
             // process local jobs before locking shared context
             while let Some(job) = self.pop_front() {
                 unsafe {
@@ -271,8 +266,16 @@ impl WorkerThread {
                 self.execute(job);
             }
 
+            // take a shared job, if it exists
+            if let Some(shared_job) = self.context.shared().jobs.remove(&self.index) {
+                self.execute(shared_job);
+            }
+
             while !latch.probe() {
-                let job = self.context.shared().pop_job();
+                let job = {
+                    let mut guard = self.context.shared();
+                    guard.jobs.remove(&self.index).or_else(|| guard.pop_job())
+                };
 
                 match job {
                     Some(job) => {
@@ -281,8 +284,6 @@ impl WorkerThread {
                         continue 'outer;
                     }
                     None => {
-                        tracing::trace!("waiting for shared job, thread id: {:?}", self.index);
-
                         // TODO: wait on latch? if we have something that can
                         // signal being done, e.g. can be waited on instead of
                         // shared jobs, we should wait on it instead, but we
@@ -297,6 +298,9 @@ impl WorkerThread {
                         // Yield? same as spinning, really, so just exit and let the upstream use wait
                         // std::thread::yield_now();
 
+                        tracing::trace!("thread {:?} is sleeping", self.index);
+
+                        latch.set_sleeping();
                         self.heartbeat.latch.wait_and_reset();
                         // since we were sleeping, the shared job can't be populated,
                         // so resuming the inner loop is fine.
@@ -339,58 +343,4 @@ impl WorkerThread {
             self.wait_until_latch_cold(latch)
         }
     }
-
-    #[inline]
-    fn wait_until_predicate<F>(&self, pred: F)
-    where
-        F: Fn() -> bool,
-    {
-        'outer: while !pred() {
-            // take a shared job, if it exists
-            if let Some(shared_job) = self.context.shared().jobs.remove(&self.index) {
-                self.execute(shared_job);
-            }
-
-            // process local jobs before locking shared context
-            while let Some(job) = self.pop_front() {
-                unsafe {
-                    job.as_ref().set_pending();
-                }
-                self.execute(job);
-            }
-
-            while !pred() {
-                let mut guard = self.context.shared();
-                let mut _spin = SpinWait::new();
-
-                match guard.pop_job() {
-                    Some(job) => {
-                        drop(guard);
-                        self.execute(job);
-
-                        continue 'outer;
-                    }
-                    None => {
-                        tracing::trace!("waiting for shared job, thread id: {:?}", self.index);
-
-                        // TODO: wait on latch? if we have something that can
-                        // signal being done, e.g. can be waited on instead of
-                        // shared jobs, we should wait on it instead, but we
-                        // would also want to receive shared jobs still?
-                        // Spin? probably just wastes CPU time.
-                        // self.context.shared_job.wait(&mut guard);
-                        // if spin.spin() {
-                        //     // wait for more shared jobs.
-                        //     // self.context.shared_job.wait(&mut guard);
-                        //     return;
-                        // }
-                        // Yield? same as spinning, really, so just exit and let the upstream use wait
-                        // std::thread::yield_now();
-                        return;
-                    }
-                }
-            }
-        }
-        return;
-    }
 }

src/praetor/mod.rs

@@ -813,7 +813,7 @@ mod job {
             }
         }
 
-        /// call this when popping value from local queue
+        /// must be called before `execute()`
         pub fn set_pending(&self) {
             let mut spin = SpinWait::new();
             loop {