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src/job/v2.rs

@@ -36,19 +36,43 @@ pub enum JobState {
     Inline = 1 << (u8::BITS - 1),
 }
 
-pub struct Job<T = ()> {
+pub struct Job<T = (), S = ()> {
     state: AtomicU8,
     this: SendPtr<()>,
-    harness: unsafe fn(*const (), *const Job<()>),
+    harness: unsafe fn(*const (), *const Job<()>, &mut S),
     maybe_boxed_val: UnsafeCell<MaybeUninit<Value<T>>>,
     waiting_thread: UnsafeCell<Option<Thread>>,
 }
 
-impl<T> Job<T> {
+impl<T, S> Job<T, S> {
+    pub unsafe fn cast_box<U, V>(self: Box<Self>) -> Box<Job<U, V>>
+    where
+        T: Sized,
+        U: Sized,
+    {
+        let ptr = Box::into_raw(self);
+
+        Box::from_raw(ptr.cast())
+    }
+
+    pub unsafe fn cast<U, V>(self: &Self) -> &Job<U, V>
+    where
+        T: Sized,
+        U: Sized,
+    {
+        // SAFETY: both T and U are sized, so Box<T> and Box<U> should be the
+        // same size as well.
+        unsafe { mem::transmute(self) }
+    }
+
+    pub fn id(&self) -> impl Eq {
+        (self.this, self.harness)
+    }
+
     pub fn state(&self) -> u8 {
         self.state.load(Ordering::Relaxed) & !(JobState::Inline as u8)
     }
-    pub fn wait(&self) -> Option<T> {
+    pub fn wait(&self) -> T {
         let mut state = self.state.load(Ordering::Relaxed);
         let mask = JobState::Inline as u8;
 
@@ -70,7 +94,7 @@ impl<T> Job<T> {
                         .store(JobState::Pending as u8 | (state & mask), Ordering::Release);
                     std::thread::park();
                     spin.reset();
-                    break;
+                    continue;
                 }
                 Err(x) => {
                     if x & JobState::Finished as u8 != 0 {
@@ -78,14 +102,13 @@ impl<T> Job<T> {
                             let value = (&*self.maybe_boxed_val.get()).assume_init_read();
                             value.get(state & JobState::Inline as u8 != 0)
                         };
-                        return Some(val);
+                        return val;
                     } else {
                         spin.spin();
                     }
                 }
             }
         }
-        return None;
     }
     /// call this when popping value from local queue
     pub fn set_pending(&self) {
@@ -110,9 +133,9 @@ impl<T> Job<T> {
         }
     }
 
-    pub fn execute(&self) {
+    pub fn execute(&self, s: &mut S) {
         // SAFETY: self is non-null
-        unsafe { (self.harness)(self.this.as_ptr().cast(), (self as *const Self).cast()) };
+        unsafe { (self.harness)(self.this.as_ptr().cast(), (self as *const Self).cast(), s) };
     }
 
     fn complete(&self, result: T) {
@@ -166,14 +189,14 @@ impl<F> HeapJob<F> {
     pub fn new(f: F) -> Box<Self> {
         Box::new(Self { f })
     }
-    pub fn into_boxed_job<T>(self: Box<Self>) -> Box<Job<()>>
+    pub fn into_boxed_job<T, S>(self: Box<Self>) -> Box<Job<(), S>>
     where
-        F: FnOnce() -> T + Send,
+        F: FnOnce(&mut S) -> T + Send,
         T: Send,
     {
-        unsafe fn harness<F, T>(this: *const (), job: *const Job<()>)
+        unsafe fn harness<F, T, S>(this: *const (), job: *const Job<()>, s: &mut S)
         where
-            F: FnOnce() -> T + Send,
+            F: FnOnce(&mut S) -> T + Send,
             T: Sized + Send,
         {
             let job = unsafe { &*job.cast::<Job<T>>() };
@@ -181,7 +204,7 @@ impl<F> HeapJob<F> {
             let this = unsafe { Box::from_raw(this.cast::<HeapJob<F>>().cast_mut()) };
             let f = this.f;
 
-            job.complete(f());
+            job.complete(f(s));
         }
 
         let size = mem::size_of::<T>();
@@ -197,12 +220,18 @@ impl<F> HeapJob<F> {
             state: AtomicU8::new(new_state),
             this: SendPtr::new(Box::into_raw(self)).unwrap().cast(),
             waiting_thread: UnsafeCell::new(None),
-            harness: harness::<F, T>,
+            harness: harness::<F, T, S>,
             maybe_boxed_val: UnsafeCell::new(MaybeUninit::uninit()),
         })
     }
 }
 
+impl<T, S> crate::latch::Probe for &Job<T, S> {
+    fn probe(&self) -> bool {
+        self.state() == JobState::Finished as u8
+    }
+}
+
 pub struct StackJob<F> {
     f: UnsafeCell<ManuallyDrop<F>>,
 }
@@ -218,14 +247,14 @@ impl<F> StackJob<F> {
         unsafe { ManuallyDrop::take(&mut *self.f.get()) }
     }
 
-    pub fn as_boxed_job<T>(&self) -> Box<Job<()>>
+    pub fn as_job<T, S>(&self) -> Job<T, S>
     where
-        F: FnOnce() -> T + Send,
+        F: FnOnce(&mut S) -> T + Send,
         T: Send,
     {
-        unsafe fn harness<F, T>(this: *const (), job: *const Job<()>)
+        unsafe fn harness<F, T, S>(this: *const (), job: *const Job<()>, s: &mut S)
         where
-            F: FnOnce() -> T + Send,
+            F: FnOnce(&mut S) -> T + Send,
             T: Sized + Send,
         {
             let job = unsafe { &*job.cast::<Job<T>>() };
@@ -233,7 +262,7 @@ impl<F> StackJob<F> {
             let this = unsafe { &*this.cast::<StackJob<F>>() };
             let f = unsafe { this.unwrap() };
 
-            job.complete(f());
+            job.complete(f(s));
         }
 
         let size = mem::size_of::<T>();
@@ -245,12 +274,12 @@ impl<F> StackJob<F> {
             JobState::Inline as u8
         };
 
-        Box::new(Job {
+        Job {
             state: AtomicU8::new(new_state),
             this: SendPtr::new(self).unwrap().cast(),
             waiting_thread: UnsafeCell::new(None),
-            harness: harness::<F, T>,
+            harness: harness::<F, T, S>,
             maybe_boxed_val: UnsafeCell::new(MaybeUninit::uninit()),
-        })
+        }
     }
 }

src/lib.rs

@@ -1,3 +1,5 @@
+#![feature(vec_deque_pop_if)]
+
 use std::{
     cell::{Cell, UnsafeCell},
     future::Future,

src/melange.rs

@@ -17,295 +17,299 @@ use parking_lot::{Condvar, Mutex};
 
 use crate::{latch::*, ThreadControl};
 mod job {
-    use std::{
+    use core::{
-        cell::{Cell, UnsafeCell},
+        cell::UnsafeCell,
-        collections::VecDeque,
+        mem::{self, ManuallyDrop, MaybeUninit},
-        mem::ManuallyDrop,
-        panic::{self, AssertUnwindSafe},
-        ptr::NonNull,
         sync::atomic::{AtomicU8, Ordering},
-        thread::{self, Thread},
     };
+    use std::thread::Thread;
 
-    use super::WorkerThread as Scope;
+    use parking_lot_core::SpinWait;
 
-    enum Poll {
+    use crate::util::SendPtr;
+
+    use super::WorkerThread;
+
+    #[allow(dead_code)]
+    #[cfg_attr(target_pointer_width = "64", repr(align(16)))]
+    #[cfg_attr(target_pointer_width = "32", repr(align(8)))]
+    #[derive(Debug, Default, Clone, Copy)]
+    struct Size2([usize; 2]);
+
+    struct Value<T>(pub MaybeUninit<Box<MaybeUninit<T>>>);
+
+    impl<T> Value<T> {
+        unsafe fn get(self, inline: bool) -> T {
+            if inline {
+                unsafe { mem::transmute_copy(&self.0) }
+            } else {
+                unsafe { (*self.0.assume_init()).assume_init() }
+            }
+        }
+    }
+
+    #[repr(u8)]
+    pub enum JobState {
+        Empty,
+        Locked = 1,
         Pending,
-        Ready,
+        Finished,
-        Locked,
+        Inline = 1 << (u8::BITS - 1),
     }
 
-    #[derive(Debug, Default)]
+    pub struct Job<T = ()> {
-    pub struct Future<T = ()> {
         state: AtomicU8,
-        /// Can only be accessed if `state` is `Poll::Locked`.
+        this: SendPtr<()>,
+        harness: unsafe fn(*const (), *const Job<()>, &mut WorkerThread),
+        maybe_boxed_val: UnsafeCell<MaybeUninit<Value<T>>>,
         waiting_thread: UnsafeCell<Option<Thread>>,
-        /// Can only be written if `state` is `Poll::Locked` and read if `state` is
-        /// `Poll::Ready`.
-        val: UnsafeCell<Option<Box<thread::Result<T>>>>,
     }
 
-    impl<T> Future<T> {
+    impl<T> Job<T> {
-        pub fn poll(&self) -> bool {
+        pub unsafe fn cast_box<U>(self: Box<Self>) -> Box<Job<U>>
-            self.state.load(Ordering::Acquire) == Poll::Ready as u8
+        where
+            T: Sized,
+            U: Sized,
+        {
+            let ptr = Box::into_raw(self);
+
+            Box::from_raw(ptr.cast())
         }
 
-        pub fn wait(&self) -> Option<thread::Result<T>> {
+        pub unsafe fn cast<U>(self: &Self) -> &Job<U>
+        where
+            T: Sized,
+            U: Sized,
+        {
+            // SAFETY: both T and U are sized, so Box<T> and Box<U> should be the
+            // same size as well.
+            unsafe { mem::transmute(self) }
+        }
+
+        pub fn state(&self) -> u8 {
+            self.state.load(Ordering::Relaxed) & !(JobState::Inline as u8)
+        }
+        pub fn wait(&self) -> T {
+            let mut state = self.state.load(Ordering::Relaxed);
+            let mask = JobState::Inline as u8;
+
+            let mut spin = SpinWait::new();
             loop {
-                let result = self.state.compare_exchange(
+                match self.state.compare_exchange(
-                    Poll::Pending as u8,
+                    JobState::Pending as u8 | (state & mask),
-                    Poll::Locked as u8,
+                    JobState::Locked as u8 | (state & mask),
-                    Ordering::AcqRel,
                     Ordering::Acquire,
-                );
+                    Ordering::Relaxed,
+                ) {
+                    Ok(x) => {
+                        state = x;
+                        unsafe {
+                            *self.waiting_thread.get() = Some(std::thread::current());
+                        }
 
-                match result {
+                        self.state
-                    Ok(_) => {
+                            .store(JobState::Pending as u8 | (state & mask), Ordering::Release);
-                        // SAFETY:
+                        std::thread::park();
-                        // Lock is acquired, only we are accessing `self.waiting_thread`.
+                        spin.reset();
-                        unsafe { *self.waiting_thread.get() = Some(thread::current()) };
-
-                        self.state.store(Poll::Pending as u8, Ordering::Release);
-
-                        thread::park();
-
-                        // Skip yielding after being woken up.
                         continue;
                     }
-                    Err(state) if state == Poll::Ready as u8 => {
+                    Err(x) => {
-                        // SAFETY:
+                        if x & JobState::Finished as u8 != 0 {
-                        // `state` is `Poll::Ready` only after `Self::complete`
+                            let val = unsafe {
-                        // releases the lock.
+                                let value = (&*self.maybe_boxed_val.get()).assume_init_read();
-                        //
+                                value.get(state & JobState::Inline as u8 != 0)
-                        // Calling `Self::complete` when `state` is `Poll::Ready`
+                            };
-                        // cannot mutate `self.val`.
+                            return val;
-                        break unsafe { (*self.val.get()).take().map(|b| *b) };
+                        } else {
+                            spin.spin();
                         }
-                    _ => (),
                     }
+                }
+            }
+        }
+        /// call this when popping value from local queue
+        pub fn set_pending(&self) {
+            let state = self.state.load(Ordering::Relaxed);
+            let mask = JobState::Inline as u8;
 
-                thread::yield_now();
+            let mut spin = SpinWait::new();
-            }
-        }
-
-        pub fn complete(&self, val: thread::Result<T>) {
-            let val = Box::new(val);
-
             loop {
-                let result = self.state.compare_exchange(
+                match self.state.compare_exchange(
-                    Poll::Pending as u8,
+                    JobState::Empty as u8 | (state & mask),
-                    Poll::Locked as u8,
+                    JobState::Pending as u8 | (state & mask),
-                    Ordering::AcqRel,
                     Ordering::Acquire,
-                );
+                    Ordering::Relaxed,
-
+                ) {
-                match result {
+                    Ok(_) => {
-                    Ok(_) => break,
+                        return;
-                    Err(_) => thread::yield_now(),
+                    }
+                    Err(_) => {
+                        spin.spin();
+                    }
+                }
+            }
+        }
+
+        pub fn execute(&self, s: &mut WorkerThread) {
+            // SAFETY: self is non-null
+            unsafe { (self.harness)(self.this.as_ptr().cast(), (self as *const Self).cast(), s) };
+        }
+
+        fn complete(&self, result: T) {
+            let mut state = self.state.load(Ordering::Relaxed);
+            let mask = JobState::Inline as u8;
+
+            let mut spin = SpinWait::new();
+            loop {
+                match self.state.compare_exchange(
+                    JobState::Pending as u8 | (state & mask),
+                    JobState::Locked as u8 | (state & mask),
+                    Ordering::Acquire,
+                    Ordering::Relaxed,
+                ) {
+                    Ok(x) => {
+                        state = x;
+                        break;
+                    }
+                    Err(_) => {
+                        spin.spin();
+                    }
                 }
             }
 
-            // SAFETY:
-            // Lock is acquired, only we are accessing `self.val`.
             unsafe {
-                *self.val.get() = Some(val);
+                let value = (&mut *self.maybe_boxed_val.get()).assume_init_mut();
+                // SAFETY: we know the box is allocated if state was `Pending`.
+                if state & JobState::Inline as u8 == 0 {
+                    value.0 = MaybeUninit::new(Box::new(MaybeUninit::new(result)));
+                } else {
+                    *mem::transmute::<_, &mut T>(&mut value.0) = result;
+                }
             }
 
-            // SAFETY:
+            if let Some(thread) = unsafe { &mut *self.waiting_thread.get() }.take() {
-            // Lock is acquired, only we are accessing `self.waiting_thread`.
-            if let Some(thread) = unsafe { (*self.waiting_thread.get()).take() } {
                 thread.unpark();
             }
 
-            self.state.store(Poll::Ready as u8, Ordering::Release);
+            self.state
+                .store(JobState::Finished as u8 | (state & mask), Ordering::Release);
         }
     }
 
-    pub struct JobStack<F = ()> {
+    impl Job {}
-        /// All code paths should call either `Job::execute` or `Self::unwrap` to
+
-        /// avoid a potential memory leak.
+    pub struct HeapJob<F> {
+        f: F,
+    }
+
+    impl<F> HeapJob<F> {
+        pub fn new(f: F) -> Box<Self> {
+            Box::new(Self { f })
+        }
+        pub fn into_boxed_job<T>(self: Box<Self>) -> Box<Job<T>>
+        where
+            F: FnOnce(&mut WorkerThread) -> T + Send,
+            T: Send,
+        {
+            unsafe fn harness<F, T>(this: *const (), job: *const Job<()>, s: &mut WorkerThread)
+            where
+                F: FnOnce(&mut WorkerThread) -> T + Send,
+                T: Sized + Send,
+            {
+                let job = unsafe { &*job.cast::<Job<T>>() };
+
+                let this = unsafe { Box::from_raw(this.cast::<HeapJob<F>>().cast_mut()) };
+                let f = this.f;
+
+                job.complete(f(s));
+            }
+
+            let size = mem::size_of::<T>();
+            let align = mem::align_of::<T>();
+
+            let new_state = if size > mem::size_of::<Box<T>>() || align > mem::align_of::<Box<T>>()
+            {
+                JobState::Empty as u8
+            } else {
+                JobState::Inline as u8
+            };
+
+            Box::new(Job {
+                state: AtomicU8::new(new_state),
+                this: SendPtr::new(Box::into_raw(self)).unwrap().cast(),
+                waiting_thread: UnsafeCell::new(None),
+                harness: harness::<F, T>,
+                maybe_boxed_val: UnsafeCell::new(MaybeUninit::uninit()),
+            })
+        }
+    }
+
+    impl<T> crate::latch::Probe for &Job<T> {
+        fn probe(&self) -> bool {
+            self.state() == JobState::Finished as u8
+        }
+    }
+
+    pub struct StackJob<F> {
         f: UnsafeCell<ManuallyDrop<F>>,
     }
 
-    impl<F> JobStack<F> {
+    impl<F> StackJob<F> {
         pub fn new(f: F) -> Self {
             Self {
                 f: UnsafeCell::new(ManuallyDrop::new(f)),
             }
         }
 
-        /// SAFETY:
+        pub unsafe fn unwrap(&self) -> F {
-        /// It should only be called once.
-        pub unsafe fn take_once(&self) -> F {
-            // SAFETY:
-            // No `Job` has has been executed, therefore `self.f` has not yet been
-            // `take`n.
             unsafe { ManuallyDrop::take(&mut *self.f.get()) }
         }
-    }
 
-    /// `Job` is only sent, not shared between threads.
+        pub fn as_job<T>(&self) -> Job<T>
-    ///
-    /// When popped from the `JobQueue`, it gets copied before sending across
-    /// thread boundaries.
-    #[derive(Clone, Debug)]
-    pub struct Job<T = ()> {
-        stack: NonNull<JobStack>,
-        harness: unsafe fn(&mut Scope, NonNull<JobStack>, NonNull<Future>),
-        fut: Cell<Option<NonNull<Future<T>>>>,
-    }
-
-    impl<T> Job<T> {
-        pub fn new<F>(stack: &JobStack<F>) -> Self
         where
-            F: FnOnce(&mut Scope) -> T + Send,
+            F: FnOnce(&mut WorkerThread) -> T + Send,
             T: Send,
         {
-            /// SAFETY:
+            unsafe fn harness<F, T>(this: *const (), job: *const Job<()>, s: &mut WorkerThread)
-            /// It should only be called while the `stack` is still alive.
+            where
-            unsafe fn harness<F, T>(
+                F: FnOnce(&mut WorkerThread) -> T + Send,
-                scope: &mut Scope,
-                stack: NonNull<JobStack>,
-                fut: NonNull<Future>,
-            ) where
-                F: FnOnce(&mut Scope) -> T + Send,
                 T: Send,
             {
-                // SAFETY:
+                let job = unsafe { &*job.cast::<Job<T>>() };
-                // The `stack` is still alive.
-                let stack: &JobStack<F> = unsafe { stack.cast().as_ref() };
-                // SAFETY:
-                // This is the first call to `take_once` since `Job::execute`
-                // (the only place where this harness is called) is called only
-                // after the job has been popped.
-                let f = unsafe { stack.take_once() };
-                // SAFETY:
-                // Before being popped, the `JobQueue` allocates and stores a
-                // `Future` in `self.fur_or_next` that should get passed here.
-                let fut: &Future<T> = unsafe { fut.cast().as_ref() };
 
-                fut.complete(panic::catch_unwind(AssertUnwindSafe(|| f(scope))));
+                let this = unsafe { &*this.cast::<StackJob<F>>() };
+                let f = unsafe { this.unwrap() };
+
+                job.complete(f(s));
             }
 
-            Self {
+            let size = mem::size_of::<T>();
-                stack: NonNull::from(stack).cast(),
+            let align = mem::align_of::<T>();
+
+            let new_state = if size > mem::size_of::<Box<T>>() || align > mem::align_of::<Box<T>>()
+            {
+                JobState::Empty as u8
+            } else {
+                JobState::Inline as u8
+            };
+
+            Job {
+                state: AtomicU8::new(new_state),
+                this: SendPtr::new(self).unwrap().cast(),
+                waiting_thread: UnsafeCell::new(None),
                 harness: harness::<F, T>,
-                fut: Cell::new(None),
+                maybe_boxed_val: UnsafeCell::new(MaybeUninit::uninit()),
             }
         }
-
-        pub fn is_waiting(&self) -> bool {
-            self.fut.get().is_none()
-        }
-
-        pub fn eq(&self, other: &Job) -> bool {
-            self.stack == other.stack
-        }
-
-        /// SAFETY:
-        /// It should only be called after being popped from a `JobQueue`.
-        pub unsafe fn poll(&self) -> bool {
-            self.fut
-                .get()
-                .map(|fut| {
-                    // SAFETY:
-                    // Before being popped, the `JobQueue` allocates and stores a
-                    // `Future` in `self.fur_or_next` that should get passed here.
-                    let fut = unsafe { fut.as_ref() };
-                    fut.poll()
-                })
-                .unwrap_or_default()
-        }
-
-        /// SAFETY:
-        /// It should only be called after being popped from a `JobQueue`.
-        pub unsafe fn wait(&self) -> Option<thread::Result<T>> {
-            self.fut.get().and_then(|fut| {
-                // SAFETY:
-                // Before being popped, the `JobQueue` allocates and stores a
-                // `Future` in `self.fur_or_next` that should get passed here.
-                let result = unsafe { fut.as_ref().wait() };
-                // SAFETY:
-                // We only can drop the `Box` *after* waiting on the `Future`
-                // in order to ensure unique access.
-                unsafe {
-                    drop(Box::from_raw(fut.as_ptr()));
-                }
-
-                result
-            })
-        }
-
-        /// SAFETY:
-        /// It should only be called in the case where the job has been popped
-        /// from the front and will not be `Job::Wait`ed.
-        pub unsafe fn drop(&self) {
-            if let Some(fut) = self.fut.get() {
-                // SAFETY:
-                // Before being popped, the `JobQueue` allocates and store a
-                // `Future` in `self.fur_or_next` that should get passed here.
-                unsafe {
-                    drop(Box::from_raw(fut.as_ptr()));
-                }
-            }
-        }
-    }
-
-    impl Job {
-        /// SAFETY:
-        /// It should only be called while the `JobStack` it was created with is
-        /// still alive and after being popped from a `JobQueue`.
-        pub unsafe fn execute(&self, scope: &mut Scope) {
-            // SAFETY:
-            // Before being popped, the `JobQueue` allocates and store a
-            // `Future` in `self.fur_or_next` that should get passed here.
-            unsafe {
-                (self.harness)(scope, self.stack, self.fut.get().unwrap());
-            }
-        }
-    }
-
-    // SAFETY:
-    // The job's `stack` will only be accessed after acquiring a lock (in
-    // `Future`), while `prev` and `fut_or_next` are never accessed after being
-    // sent across threads.
-    unsafe impl Send for Job {}
-
-    #[derive(Debug, Default)]
-    pub struct JobQueue(VecDeque<NonNull<Job>>);
-
-    impl JobQueue {
-        pub fn len(&self) -> usize {
-            self.0.len()
-        }
-
-        /// SAFETY:
-        /// Any `Job` pushed onto the queue should alive at least until it gets
-        /// popped.
-        pub unsafe fn push_back<T>(&mut self, job: &Job<T>) {
-            self.0.push_back(NonNull::from(job).cast());
-        }
-
-        pub fn pop_back(&mut self) {
-            self.0.pop_back();
-        }
-
-        pub fn pop_front(&mut self) -> Option<Job> {
-            // SAFETY:
-            // `Job` is still alive as per contract in `push_back`.
-            let job = unsafe { self.0.pop_front()?.as_ref() };
-            job.fut
-                .set(Some(Box::leak(Box::new(Future::default())).into()));
-
-            Some(job.clone())
-        }
     }
 }
 
 //use job::{Future, Job, JobQueue, JobStack};
-use crate::job::v2::{Job, JobState, StackJob};
+use crate::job::v2::{Job as JobArchetype, JobState, StackJob};
 // use crate::job::{Job, JobRef, StackJob};
 
+type Job<T = ()> = JobArchetype<T, WorkerThread>;
+
 struct ThreadState {
     control: ThreadControl,
 }
@@ -320,6 +324,9 @@ pub struct SharedContext {
     rng: crate::rng::XorShift64Star,
 }
 
+// SAFETY: Job is Send
+unsafe impl Send for SharedContext {}
+
 pub struct Context {
     shared: Mutex<SharedContext>,
     threads: Box<[CachePadded<ThreadState>]>,
@@ -360,17 +367,13 @@ impl SharedContext {
             .next()
     }
 
-    fn pop_random_task(&mut self) -> Option<JobRef> {
+    fn pop_random_task(&mut self) -> Option<NonNull<Job>> {
         let i = self.rng.next_usize(self.shared_tasks.len());
         let (a, b) = self.shared_tasks.split_at_mut(i);
         a.into_iter().chain(b).filter_map(|task| task.take()).next()
     }
 }
 
-std::thread_local! {
-    static WORKER_THREAD_STATE: Cell<*const WorkerThread> = const { Cell::new(ptr::null())};
-}
-
 pub struct WorkerThread {
     context: Arc<Context>,
     index: usize,
@@ -381,6 +384,9 @@ pub struct WorkerThread {
     _marker: PhantomPinned,
 }
 
+// SAFETY: Job is Send
+unsafe impl Send for WorkerThread {}
+
 impl WorkerThread {
     fn new(context: Arc<Context>, heartbeat: Arc<AtomicBool>, index: usize) -> WorkerThread {
         WorkerThread {
@@ -393,23 +399,6 @@ impl WorkerThread {
             _marker: PhantomPinned,
         }
     }
-    unsafe fn set_current(this: *const Self) {
-        WORKER_THREAD_STATE.with(|ptr| {
-            assert!(ptr.get().is_null());
-            ptr.set(this);
-        });
-    }
-    unsafe fn unset_current() {
-        WORKER_THREAD_STATE.with(|ptr| {
-            assert!(!ptr.get().is_null());
-            ptr.set(ptr::null());
-        });
-    }
-    unsafe fn current() -> *const WorkerThread {
-        let ptr = WORKER_THREAD_STATE.with(|ptr| ptr.get());
-
-        ptr
-    }
     fn state(&self) -> &CachePadded<ThreadState> {
         &self.context.threads[self.index]
     }
@@ -422,89 +411,33 @@ impl WorkerThread {
     fn ctx(&self) -> &Arc<Context> {
         &self.context
     }
-
-    fn with<T, F: FnOnce(Option<&WorkerThread>) -> T>(f: F) -> T {
-        WORKER_THREAD_STATE.with(|worker| {
-            f(unsafe { NonNull::new(worker.get().cast_mut()).map(|ptr| ptr.as_ref()) })
-        })
 }
 
-    fn with_mut<T, F: FnOnce(Option<&mut WorkerThread>) -> T>(f: F) -> T {
-        WORKER_THREAD_STATE.with(|worker| {
-            f(unsafe { NonNull::new(worker.get().cast_mut()).map(|mut ptr| ptr.as_mut()) })
-        })
-    }
-}
-
-struct CurrentWorker;
-
-impl Deref for CurrentWorker {
-    type Target = WorkerThread;
-
-    fn deref(&self) -> &Self::Target {
-        unsafe {
-            NonNull::new(WorkerThread::current().cast_mut())
-                .unwrap()
-                .as_ref()
-        }
-    }
-}
-
-impl DerefMut for CurrentWorker {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        unsafe {
-            NonNull::new(WorkerThread::current().cast_mut())
-                .unwrap()
-                .as_mut()
-        }
-    }
-}
-
-// impl Drop for WorkerThread {
-//     fn drop(&mut self) {
-//         WORKER_THREAD_STATE.with(|ptr| {
-//             assert!(!ptr.get().is_null());
-//             ptr.set(ptr::null());
-//         });
-//     }
-// }
-
 impl WorkerThread {
-    fn worker(self) {
+    fn worker(mut self) {
-        {
+        self.control().notify_running();
-            let worker = Box::leak(Box::new(self));
-            unsafe {
-                WorkerThread::set_current(worker);
-            }
-        }
-
-        CurrentWorker.control().notify_running();
 
         loop {
-            let task = { CurrentWorker.shared().lock().pop_first_task() };
+            let task = { self.shared().lock().pop_first_task() };
 
             if let Some(task) = task {
-                CurrentWorker.execute_job(task);
+                self.execute_job(task);
             }
 
-            if CurrentWorker.control().should_terminate.probe() {
+            if self.control().should_terminate.probe() {
                 break;
             }
 
-            let mut guard = CurrentWorker.shared().lock();
+            let mut guard = self.shared().lock();
-            CurrentWorker.ctx().task_shared.wait(&mut guard);
+            self.ctx().task_shared.wait(&mut guard);
         }
 
-        CurrentWorker.control().notify_termination();
+        self.control().notify_termination();
-        unsafe {
-            let worker = Box::from_raw(WorkerThread::current().cast_mut());
-            WorkerThread::unset_current();
-        }
     }
 
     fn execute_job(&mut self, job: NonNull<Job>) {
         unsafe {
-            job.as_ref().execute();
+            job.as_ref().execute(self);
         }
     }
 
@@ -568,44 +501,30 @@ impl WorkerThread {
         RA: Send,
         RB: Send,
     {
-        let mut ra = None;
+        let b = StackJob::new(b);
-        let latch = AtomicLatch::new();
-        let a = |scope: &mut WorkerThread| {
-            if scope.heartbeat.load(Ordering::Relaxed) {
-                scope.heartbeat_cold();
-            }
 
-            ra = Some(a(scope));
+        let job = Box::new(b.as_job());
-            unsafe {
+        self.queue
-                Latch::set_raw(&latch);
+            .push_back(unsafe { NonNull::new_unchecked(&job as *const _ as *mut _) });
-            }
+        let job = unsafe { job.cast_box::<RB, Self>() };
+
+        let ra = a(self);
+
+        let rb = if job.state() == JobState::Empty as u8 {
+            self.pop_job_id(unsafe { job.as_ref().cast() });
+            unsafe { b.unwrap()(self) }
+        } else {
+            self.run_until(&job.as_ref());
+            job.wait()
         };
 
-        let stack = StackJob::new(a);
+        (ra, rb)
-        let task: JobRef =
-            unsafe { core::mem::transmute::<JobRef<_>, JobRef>(stack.as_task_ref()) };
-
-        let id = task.id();
-        self.queue.push_back(task);
-
-        let rb = b(self);
-
-        if !latch.probe() {
-            if let Some(job) = self.queue.pop_back() {
-                if job.id() == id {
-                    unsafe {
-                        (stack.take_once())(self);
-                    }
-                    return (ra.unwrap(), rb);
-                } else {
-                    self.queue.push_back(job);
-                }
-            }
     }
 
-        self.run_until(&latch);
+    fn pop_job_id(&mut self, id: &Job) -> Option<&Job<()>> {
-
+        self.queue
-        (ra.unwrap(), rb)
+            .pop_back_if(|job| unsafe { (&*job).as_ref().id() == id.id() })
+            .map(|job| unsafe { job.as_ref() })
     }
 
     fn run_until<L: Probe>(&mut self, latch: &L) {

src/util.rs

@@ -4,7 +4,7 @@ use core::{
     ptr::NonNull,
 };
 
-#[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+#[derive(Debug, PartialEq, Eq, Hash, PartialOrd, Ord, Clone, Copy)]
 #[repr(transparent)]
 pub struct SendPtr<T>(NonNull<T>);