Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 769 insertions, 0 deletions

diff --git a/vendor/rayon-core/src/scope/mod.rs b/vendor/rayon-core/src/scope/mod.rs
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+//! Methods for custom fork-join scopes, created by the [`scope()`]
+//! and [`in_place_scope()`] functions. These are a more flexible alternative to [`join()`].
+//!
+//! [`scope()`]: fn.scope.html
+//! [`in_place_scope()`]: fn.in_place_scope.html
+//! [`join()`]: ../join/join.fn.html
+
+use crate::broadcast::BroadcastContext;
+use crate::job::{ArcJob, HeapJob, JobFifo, JobRef};
+use crate::latch::{CountLatch, Latch};
+use crate::registry::{global_registry, in_worker, Registry, WorkerThread};
+use crate::unwind;
+use std::any::Any;
+use std::fmt;
+use std::marker::PhantomData;
+use std::mem::ManuallyDrop;
+use std::ptr;
+use std::sync::atomic::{AtomicPtr, Ordering};
+use std::sync::Arc;
+
+#[cfg(test)]
+mod test;
+
+/// Represents a fork-join scope which can be used to spawn any number of tasks.
+/// See [`scope()`] for more information.
+///
+///[`scope()`]: fn.scope.html
+pub struct Scope<'scope> {
+    base: ScopeBase<'scope>,
+}
+
+/// Represents a fork-join scope which can be used to spawn any number of tasks.
+/// Those spawned from the same thread are prioritized in relative FIFO order.
+/// See [`scope_fifo()`] for more information.
+///
+///[`scope_fifo()`]: fn.scope_fifo.html
+pub struct ScopeFifo<'scope> {
+    base: ScopeBase<'scope>,
+    fifos: Vec<JobFifo>,
+}
+
+struct ScopeBase<'scope> {
+    /// thread registry where `scope()` was executed or where `in_place_scope()`
+    /// should spawn jobs.
+    registry: Arc<Registry>,
+
+    /// if some job panicked, the error is stored here; it will be
+    /// propagated to the one who created the scope
+    panic: AtomicPtr<Box<dyn Any + Send + 'static>>,
+
+    /// latch to track job counts
+    job_completed_latch: CountLatch,
+
+    /// You can think of a scope as containing a list of closures to execute,
+    /// all of which outlive `'scope`.  They're not actually required to be
+    /// `Sync`, but it's still safe to let the `Scope` implement `Sync` because
+    /// the closures are only *moved* across threads to be executed.
+    marker: PhantomData<Box<dyn FnOnce(&Scope<'scope>) + Send + Sync + 'scope>>,
+}
+
+/// Creates a "fork-join" scope `s` and invokes the closure with a
+/// reference to `s`. This closure can then spawn asynchronous tasks
+/// into `s`. Those tasks may run asynchronously with respect to the
+/// closure; they may themselves spawn additional tasks into `s`. When
+/// the closure returns, it will block until all tasks that have been
+/// spawned into `s` complete.
+///
+/// `scope()` is a more flexible building block compared to `join()`,
+/// since a loop can be used to spawn any number of tasks without
+/// recursing. However, that flexibility comes at a performance price:
+/// tasks spawned using `scope()` must be allocated onto the heap,
+/// whereas `join()` can make exclusive use of the stack. **Prefer
+/// `join()` (or, even better, parallel iterators) where possible.**
+///
+/// # Example
+///
+/// The Rayon `join()` function launches two closures and waits for them
+/// to stop. One could implement `join()` using a scope like so, although
+/// it would be less efficient than the real implementation:
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// pub fn join<A,B,RA,RB>(oper_a: A, oper_b: B) -> (RA, RB)
+///     where A: FnOnce() -> RA + Send,
+///           B: FnOnce() -> RB + Send,
+///           RA: Send,
+///           RB: Send,
+/// {
+///     let mut result_a: Option<RA> = None;
+///     let mut result_b: Option<RB> = None;
+///     rayon::scope(|s| {
+///         s.spawn(|_| result_a = Some(oper_a()));
+///         s.spawn(|_| result_b = Some(oper_b()));
+///     });
+///     (result_a.unwrap(), result_b.unwrap())
+/// }
+/// ```
+///
+/// # A note on threading
+///
+/// The closure given to `scope()` executes in the Rayon thread-pool,
+/// as do those given to `spawn()`. This means that you can't access
+/// thread-local variables (well, you can, but they may have
+/// unexpected values).
+///
+/// # Task execution
+///
+/// Task execution potentially starts as soon as `spawn()` is called.
+/// The task will end sometime before `scope()` returns. Note that the
+/// *closure* given to scope may return much earlier. In general
+/// the lifetime of a scope created like `scope(body)` goes something like this:
+///
+/// - Scope begins when `scope(body)` is called
+/// - Scope body `body()` is invoked
+///     - Scope tasks may be spawned
+/// - Scope body returns
+/// - Scope tasks execute, possibly spawning more tasks
+/// - Once all tasks are done, scope ends and `scope()` returns
+///
+/// To see how and when tasks are joined, consider this example:
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// // point start
+/// rayon::scope(|s| {
+///     s.spawn(|s| { // task s.1
+///         s.spawn(|s| { // task s.1.1
+///             rayon::scope(|t| {
+///                 t.spawn(|_| ()); // task t.1
+///                 t.spawn(|_| ()); // task t.2
+///             });
+///         });
+///     });
+///     s.spawn(|s| { // task s.2
+///     });
+///     // point mid
+/// });
+/// // point end
+/// ```
+///
+/// The various tasks that are run will execute roughly like so:
+///
+/// ```notrust
+/// | (start)
+/// |
+/// | (scope `s` created)
+/// +-----------------------------------------------+ (task s.2)
+/// +-------+ (task s.1)                            |
+/// |       |                                       |
+/// |       +---+ (task s.1.1)                      |
+/// |       |   |                                   |
+/// |       |   | (scope `t` created)               |
+/// |       |   +----------------+ (task t.2)       |
+/// |       |   +---+ (task t.1) |                  |
+/// | (mid) |   |   |            |                  |
+/// :       |   + <-+------------+ (scope `t` ends) |
+/// :       |   |                                   |
+/// |<------+---+-----------------------------------+ (scope `s` ends)
+/// |
+/// | (end)
+/// ```
+///
+/// The point here is that everything spawned into scope `s` will
+/// terminate (at latest) at the same point -- right before the
+/// original call to `rayon::scope` returns. This includes new
+/// subtasks created by other subtasks (e.g., task `s.1.1`). If a new
+/// scope is created (such as `t`), the things spawned into that scope
+/// will be joined before that scope returns, which in turn occurs
+/// before the creating task (task `s.1.1` in this case) finishes.
+///
+/// There is no guaranteed order of execution for spawns in a scope,
+/// given that other threads may steal tasks at any time. However, they
+/// are generally prioritized in a LIFO order on the thread from which
+/// they were spawned. So in this example, absent any stealing, we can
+/// expect `s.2` to execute before `s.1`, and `t.2` before `t.1`. Other
+/// threads always steal from the other end of the deque, like FIFO
+/// order.  The idea is that "recent" tasks are most likely to be fresh
+/// in the local CPU's cache, while other threads can steal older
+/// "stale" tasks.  For an alternate approach, consider
+/// [`scope_fifo()`] instead.
+///
+/// [`scope_fifo()`]: fn.scope_fifo.html
+///
+/// # Accessing stack data
+///
+/// In general, spawned tasks may access stack data in place that
+/// outlives the scope itself. Other data must be fully owned by the
+/// spawned task.
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// let ok: Vec<i32> = vec![1, 2, 3];
+/// rayon::scope(|s| {
+///     let bad: Vec<i32> = vec![4, 5, 6];
+///     s.spawn(|_| {
+///         // We can access `ok` because outlives the scope `s`.
+///         println!("ok: {:?}", ok);
+///
+///         // If we just try to use `bad` here, the closure will borrow `bad`
+///         // (because we are just printing it out, and that only requires a
+///         // borrow), which will result in a compilation error. Read on
+///         // for options.
+///         // println!("bad: {:?}", bad);
+///    });
+/// });
+/// ```
+///
+/// As the comments example above suggest, to reference `bad` we must
+/// take ownership of it. One way to do this is to detach the closure
+/// from the surrounding stack frame, using the `move` keyword. This
+/// will cause it to take ownership of *all* the variables it touches,
+/// in this case including both `ok` *and* `bad`:
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// let ok: Vec<i32> = vec![1, 2, 3];
+/// rayon::scope(|s| {
+///     let bad: Vec<i32> = vec![4, 5, 6];
+///     s.spawn(move |_| {
+///         println!("ok: {:?}", ok);
+///         println!("bad: {:?}", bad);
+///     });
+///
+///     // That closure is fine, but now we can't use `ok` anywhere else,
+///     // since it is owned by the previous task:
+///     // s.spawn(|_| println!("ok: {:?}", ok));
+/// });
+/// ```
+///
+/// While this works, it could be a problem if we want to use `ok` elsewhere.
+/// There are two choices. We can keep the closure as a `move` closure, but
+/// instead of referencing the variable `ok`, we create a shadowed variable that
+/// is a borrow of `ok` and capture *that*:
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// let ok: Vec<i32> = vec![1, 2, 3];
+/// rayon::scope(|s| {
+///     let bad: Vec<i32> = vec![4, 5, 6];
+///     let ok: &Vec<i32> = &ok; // shadow the original `ok`
+///     s.spawn(move |_| {
+///         println!("ok: {:?}", ok); // captures the shadowed version
+///         println!("bad: {:?}", bad);
+///     });
+///
+///     // Now we too can use the shadowed `ok`, since `&Vec<i32>` references
+///     // can be shared freely. Note that we need a `move` closure here though,
+///     // because otherwise we'd be trying to borrow the shadowed `ok`,
+///     // and that doesn't outlive `scope`.
+///     s.spawn(move |_| println!("ok: {:?}", ok));
+/// });
+/// ```
+///
+/// Another option is not to use the `move` keyword but instead to take ownership
+/// of individual variables:
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// let ok: Vec<i32> = vec![1, 2, 3];
+/// rayon::scope(|s| {
+///     let bad: Vec<i32> = vec![4, 5, 6];
+///     s.spawn(|_| {
+///         // Transfer ownership of `bad` into a local variable (also named `bad`).
+///         // This will force the closure to take ownership of `bad` from the environment.
+///         let bad = bad;
+///         println!("ok: {:?}", ok); // `ok` is only borrowed.
+///         println!("bad: {:?}", bad); // refers to our local variable, above.
+///     });
+///
+///     s.spawn(|_| println!("ok: {:?}", ok)); // we too can borrow `ok`
+/// });
+/// ```
+///
+/// # Panics
+///
+/// If a panic occurs, either in the closure given to `scope()` or in
+/// any of the spawned jobs, that panic will be propagated and the
+/// call to `scope()` will panic. If multiple panics occurs, it is
+/// non-deterministic which of their panic values will propagate.
+/// Regardless, once a task is spawned using `scope.spawn()`, it will
+/// execute, even if the spawning task should later panic. `scope()`
+/// returns once all spawned jobs have completed, and any panics are
+/// propagated at that point.
+pub fn scope<'scope, OP, R>(op: OP) -> R
+where
+    OP: FnOnce(&Scope<'scope>) -> R + Send,
+    R: Send,
+{
+    in_worker(|owner_thread, _| {
+        let scope = Scope::<'scope>::new(Some(owner_thread), None);
+        scope.base.complete(Some(owner_thread), || op(&scope))
+    })
+}
+
+/// Creates a "fork-join" scope `s` with FIFO order, and invokes the
+/// closure with a reference to `s`. This closure can then spawn
+/// asynchronous tasks into `s`. Those tasks may run asynchronously with
+/// respect to the closure; they may themselves spawn additional tasks
+/// into `s`. When the closure returns, it will block until all tasks
+/// that have been spawned into `s` complete.
+///
+/// # Task execution
+///
+/// Tasks in a `scope_fifo()` run similarly to [`scope()`], but there's a
+/// difference in the order of execution. Consider a similar example:
+///
+/// [`scope()`]: fn.scope.html
+///
+/// ```rust
+/// # use rayon_core as rayon;
+/// // point start
+/// rayon::scope_fifo(|s| {
+///     s.spawn_fifo(|s| { // task s.1
+///         s.spawn_fifo(|s| { // task s.1.1
+///             rayon::scope_fifo(|t| {
+///                 t.spawn_fifo(|_| ()); // task t.1
+///                 t.spawn_fifo(|_| ()); // task t.2
+///             });
+///         });
+///     });
+///     s.spawn_fifo(|s| { // task s.2
+///     });
+///     // point mid
+/// });
+/// // point end
+/// ```
+///
+/// The various tasks that are run will execute roughly like so:
+///
+/// ```notrust
+/// | (start)
+/// |
+/// | (FIFO scope `s` created)
+/// +--------------------+ (task s.1)
+/// +-------+ (task s.2) |
+/// |       |            +---+ (task s.1.1)
+/// |       |            |   |
+/// |       |            |   | (FIFO scope `t` created)
+/// |       |            |   +----------------+ (task t.1)
+/// |       |            |   +---+ (task t.2) |
+/// | (mid) |            |   |   |            |
+/// :       |            |   + <-+------------+ (scope `t` ends)
+/// :       |            |   |
+/// |<------+------------+---+ (scope `s` ends)
+/// |
+/// | (end)
+/// ```
+///
+/// Under `scope_fifo()`, the spawns are prioritized in a FIFO order on
+/// the thread from which they were spawned, as opposed to `scope()`'s
+/// LIFO.  So in this example, we can expect `s.1` to execute before
+/// `s.2`, and `t.1` before `t.2`. Other threads also steal tasks in
+/// FIFO order, as usual. Overall, this has roughly the same order as
+/// the now-deprecated [`breadth_first`] option, except the effect is
+/// isolated to a particular scope. If spawns are intermingled from any
+/// combination of `scope()` and `scope_fifo()`, or from different
+/// threads, their order is only specified with respect to spawns in the
+/// same scope and thread.
+///
+/// For more details on this design, see Rayon [RFC #1].
+///
+/// [`breadth_first`]: struct.ThreadPoolBuilder.html#method.breadth_first
+/// [RFC #1]: https://github.com/rayon-rs/rfcs/blob/master/accepted/rfc0001-scope-scheduling.md
+///
+/// # Panics
+///
+/// If a panic occurs, either in the closure given to `scope_fifo()` or
+/// in any of the spawned jobs, that panic will be propagated and the
+/// call to `scope_fifo()` will panic. If multiple panics occurs, it is
+/// non-deterministic which of their panic values will propagate.
+/// Regardless, once a task is spawned using `scope.spawn_fifo()`, it
+/// will execute, even if the spawning task should later panic.
+/// `scope_fifo()` returns once all spawned jobs have completed, and any
+/// panics are propagated at that point.
+pub fn scope_fifo<'scope, OP, R>(op: OP) -> R
+where
+    OP: FnOnce(&ScopeFifo<'scope>) -> R + Send,
+    R: Send,
+{
+    in_worker(|owner_thread, _| {
+        let scope = ScopeFifo::<'scope>::new(Some(owner_thread), None);
+        scope.base.complete(Some(owner_thread), || op(&scope))
+    })
+}
+
+/// Creates a "fork-join" scope `s` and invokes the closure with a
+/// reference to `s`. This closure can then spawn asynchronous tasks
+/// into `s`. Those tasks may run asynchronously with respect to the
+/// closure; they may themselves spawn additional tasks into `s`. When
+/// the closure returns, it will block until all tasks that have been
+/// spawned into `s` complete.
+///
+/// This is just like `scope()` except the closure runs on the same thread
+/// that calls `in_place_scope()`. Only work that it spawns runs in the
+/// thread pool.
+///
+/// # Panics
+///
+/// If a panic occurs, either in the closure given to `in_place_scope()` or in
+/// any of the spawned jobs, that panic will be propagated and the
+/// call to `in_place_scope()` will panic. If multiple panics occurs, it is
+/// non-deterministic which of their panic values will propagate.
+/// Regardless, once a task is spawned using `scope.spawn()`, it will
+/// execute, even if the spawning task should later panic. `in_place_scope()`
+/// returns once all spawned jobs have completed, and any panics are
+/// propagated at that point.
+pub fn in_place_scope<'scope, OP, R>(op: OP) -> R
+where
+    OP: FnOnce(&Scope<'scope>) -> R,
+{
+    do_in_place_scope(None, op)
+}
+
+pub(crate) fn do_in_place_scope<'scope, OP, R>(registry: Option<&Arc<Registry>>, op: OP) -> R
+where
+    OP: FnOnce(&Scope<'scope>) -> R,
+{
+    let thread = unsafe { WorkerThread::current().as_ref() };
+    let scope = Scope::<'scope>::new(thread, registry);
+    scope.base.complete(thread, || op(&scope))
+}
+
+/// Creates a "fork-join" scope `s` with FIFO order, and invokes the
+/// closure with a reference to `s`. This closure can then spawn
+/// asynchronous tasks into `s`. Those tasks may run asynchronously with
+/// respect to the closure; they may themselves spawn additional tasks
+/// into `s`. When the closure returns, it will block until all tasks
+/// that have been spawned into `s` complete.
+///
+/// This is just like `scope_fifo()` except the closure runs on the same thread
+/// that calls `in_place_scope_fifo()`. Only work that it spawns runs in the
+/// thread pool.
+///
+/// # Panics
+///
+/// If a panic occurs, either in the closure given to `in_place_scope_fifo()` or in
+/// any of the spawned jobs, that panic will be propagated and the
+/// call to `in_place_scope_fifo()` will panic. If multiple panics occurs, it is
+/// non-deterministic which of their panic values will propagate.
+/// Regardless, once a task is spawned using `scope.spawn_fifo()`, it will
+/// execute, even if the spawning task should later panic. `in_place_scope_fifo()`
+/// returns once all spawned jobs have completed, and any panics are
+/// propagated at that point.
+pub fn in_place_scope_fifo<'scope, OP, R>(op: OP) -> R
+where
+    OP: FnOnce(&ScopeFifo<'scope>) -> R,
+{
+    do_in_place_scope_fifo(None, op)
+}
+
+pub(crate) fn do_in_place_scope_fifo<'scope, OP, R>(registry: Option<&Arc<Registry>>, op: OP) -> R
+where
+    OP: FnOnce(&ScopeFifo<'scope>) -> R,
+{
+    let thread = unsafe { WorkerThread::current().as_ref() };
+    let scope = ScopeFifo::<'scope>::new(thread, registry);
+    scope.base.complete(thread, || op(&scope))
+}
+
+impl<'scope> Scope<'scope> {
+    fn new(owner: Option<&WorkerThread>, registry: Option<&Arc<Registry>>) -> Self {
+        let base = ScopeBase::new(owner, registry);
+        Scope { base }
+    }
+
+    /// Spawns a job into the fork-join scope `self`. This job will
+    /// execute sometime before the fork-join scope completes.  The
+    /// job is specified as a closure, and this closure receives its
+    /// own reference to the scope `self` as argument. This can be
+    /// used to inject new jobs into `self`.
+    ///
+    /// # Returns
+    ///
+    /// Nothing. The spawned closures cannot pass back values to the
+    /// caller directly, though they can write to local variables on
+    /// the stack (if those variables outlive the scope) or
+    /// communicate through shared channels.
+    ///
+    /// (The intention is to eventually integrate with Rust futures to
+    /// support spawns of functions that compute a value.)
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use rayon_core as rayon;
+    /// let mut value_a = None;
+    /// let mut value_b = None;
+    /// let mut value_c = None;
+    /// rayon::scope(|s| {
+    ///     s.spawn(|s1| {
+    ///           // ^ this is the same scope as `s`; this handle `s1`
+    ///           //   is intended for use by the spawned task,
+    ///           //   since scope handles cannot cross thread boundaries.
+    ///
+    ///         value_a = Some(22);
+    ///
+    ///         // the scope `s` will not end until all these tasks are done
+    ///         s1.spawn(|_| {
+    ///             value_b = Some(44);
+    ///         });
+    ///     });
+    ///
+    ///     s.spawn(|_| {
+    ///         value_c = Some(66);
+    ///     });
+    /// });
+    /// assert_eq!(value_a, Some(22));
+    /// assert_eq!(value_b, Some(44));
+    /// assert_eq!(value_c, Some(66));
+    /// ```
+    ///
+    /// # See also
+    ///
+    /// The [`scope` function] has more extensive documentation about
+    /// task spawning.
+    ///
+    /// [`scope` function]: fn.scope.html
+    pub fn spawn<BODY>(&self, body: BODY)
+    where
+        BODY: FnOnce(&Scope<'scope>) + Send + 'scope,
+    {
+        let scope_ptr = ScopePtr(self);
+        let job = HeapJob::new(move || unsafe {
+            // SAFETY: this job will execute before the scope ends.
+            let scope = scope_ptr.as_ref();
+            ScopeBase::execute_job(&scope.base, move || body(scope))
+        });
+        let job_ref = self.base.heap_job_ref(job);
+
+        // Since `Scope` implements `Sync`, we can't be sure that we're still in a
+        // thread of this pool, so we can't just push to the local worker thread.
+        // Also, this might be an in-place scope.
+        self.base.registry.inject_or_push(job_ref);
+    }
+
+    /// Spawns a job into every thread of the fork-join scope `self`. This job will
+    /// execute on each thread sometime before the fork-join scope completes.  The
+    /// job is specified as a closure, and this closure receives its own reference
+    /// to the scope `self` as argument, as well as a `BroadcastContext`.
+    pub fn spawn_broadcast<BODY>(&self, body: BODY)
+    where
+        BODY: Fn(&Scope<'scope>, BroadcastContext<'_>) + Send + Sync + 'scope,
+    {
+        let scope_ptr = ScopePtr(self);
+        let job = ArcJob::new(move || unsafe {
+            // SAFETY: this job will execute before the scope ends.
+            let scope = scope_ptr.as_ref();
+            let body = &body;
+            let func = move || BroadcastContext::with(move |ctx| body(scope, ctx));
+            ScopeBase::execute_job(&scope.base, func)
+        });
+        self.base.inject_broadcast(job)
+    }
+}
+
+impl<'scope> ScopeFifo<'scope> {
+    fn new(owner: Option<&WorkerThread>, registry: Option<&Arc<Registry>>) -> Self {
+        let base = ScopeBase::new(owner, registry);
+        let num_threads = base.registry.num_threads();
+        let fifos = (0..num_threads).map(|_| JobFifo::new()).collect();
+        ScopeFifo { base, fifos }
+    }
+
+    /// Spawns a job into the fork-join scope `self`. This job will
+    /// execute sometime before the fork-join scope completes.  The
+    /// job is specified as a closure, and this closure receives its
+    /// own reference to the scope `self` as argument. This can be
+    /// used to inject new jobs into `self`.
+    ///
+    /// # See also
+    ///
+    /// This method is akin to [`Scope::spawn()`], but with a FIFO
+    /// priority.  The [`scope_fifo` function] has more details about
+    /// this distinction.
+    ///
+    /// [`Scope::spawn()`]: struct.Scope.html#method.spawn
+    /// [`scope_fifo` function]: fn.scope_fifo.html
+    pub fn spawn_fifo<BODY>(&self, body: BODY)
+    where
+        BODY: FnOnce(&ScopeFifo<'scope>) + Send + 'scope,
+    {
+        let scope_ptr = ScopePtr(self);
+        let job = HeapJob::new(move || unsafe {
+            // SAFETY: this job will execute before the scope ends.
+            let scope = scope_ptr.as_ref();
+            ScopeBase::execute_job(&scope.base, move || body(scope))
+        });
+        let job_ref = self.base.heap_job_ref(job);
+
+        // If we're in the pool, use our scope's private fifo for this thread to execute
+        // in a locally-FIFO order. Otherwise, just use the pool's global injector.
+        match self.base.registry.current_thread() {
+            Some(worker) => {
+                let fifo = &self.fifos[worker.index()];
+                // SAFETY: this job will execute before the scope ends.
+                unsafe { worker.push(fifo.push(job_ref)) };
+            }
+            None => self.base.registry.inject(job_ref),
+        }
+    }
+
+    /// Spawns a job into every thread of the fork-join scope `self`. This job will
+    /// execute on each thread sometime before the fork-join scope completes.  The
+    /// job is specified as a closure, and this closure receives its own reference
+    /// to the scope `self` as argument, as well as a `BroadcastContext`.
+    pub fn spawn_broadcast<BODY>(&self, body: BODY)
+    where
+        BODY: Fn(&ScopeFifo<'scope>, BroadcastContext<'_>) + Send + Sync + 'scope,
+    {
+        let scope_ptr = ScopePtr(self);
+        let job = ArcJob::new(move || unsafe {
+            // SAFETY: this job will execute before the scope ends.
+            let scope = scope_ptr.as_ref();
+            let body = &body;
+            let func = move || BroadcastContext::with(move |ctx| body(scope, ctx));
+            ScopeBase::execute_job(&scope.base, func)
+        });
+        self.base.inject_broadcast(job)
+    }
+}
+
+impl<'scope> ScopeBase<'scope> {
+    /// Creates the base of a new scope for the given registry
+    fn new(owner: Option<&WorkerThread>, registry: Option<&Arc<Registry>>) -> Self {
+        let registry = registry.unwrap_or_else(|| match owner {
+            Some(owner) => owner.registry(),
+            None => global_registry(),
+        });
+
+        ScopeBase {
+            registry: Arc::clone(registry),
+            panic: AtomicPtr::new(ptr::null_mut()),
+            job_completed_latch: CountLatch::new(owner),
+            marker: PhantomData,
+        }
+    }
+
+    fn heap_job_ref<FUNC>(&self, job: Box<HeapJob<FUNC>>) -> JobRef
+    where
+        FUNC: FnOnce() + Send + 'scope,
+    {
+        unsafe {
+            self.job_completed_latch.increment();
+            job.into_job_ref()
+        }
+    }
+
+    fn inject_broadcast<FUNC>(&self, job: Arc<ArcJob<FUNC>>)
+    where
+        FUNC: Fn() + Send + Sync + 'scope,
+    {
+        let n_threads = self.registry.num_threads();
+        let job_refs = (0..n_threads).map(|_| unsafe {
+            self.job_completed_latch.increment();
+            ArcJob::as_job_ref(&job)
+        });
+
+        self.registry.inject_broadcast(job_refs);
+    }
+
+    /// Executes `func` as a job, either aborting or executing as
+    /// appropriate.
+    fn complete<FUNC, R>(&self, owner: Option<&WorkerThread>, func: FUNC) -> R
+    where
+        FUNC: FnOnce() -> R,
+    {
+        let result = unsafe { Self::execute_job_closure(self, func) };
+        self.job_completed_latch.wait(owner);
+        self.maybe_propagate_panic();
+        result.unwrap() // only None if `op` panicked, and that would have been propagated
+    }
+
+    /// Executes `func` as a job, either aborting or executing as
+    /// appropriate.
+    unsafe fn execute_job<FUNC>(this: *const Self, func: FUNC)
+    where
+        FUNC: FnOnce(),
+    {
+        let _: Option<()> = Self::execute_job_closure(this, func);
+    }
+
+    /// Executes `func` as a job in scope. Adjusts the "job completed"
+    /// counters and also catches any panic and stores it into
+    /// `scope`.
+    unsafe fn execute_job_closure<FUNC, R>(this: *const Self, func: FUNC) -> Option<R>
+    where
+        FUNC: FnOnce() -> R,
+    {
+        let result = match unwind::halt_unwinding(func) {
+            Ok(r) => Some(r),
+            Err(err) => {
+                (*this).job_panicked(err);
+                None
+            }
+        };
+        Latch::set(&(*this).job_completed_latch);
+        result
+    }
+
+    fn job_panicked(&self, err: Box<dyn Any + Send + 'static>) {
+        // capture the first error we see, free the rest
+        if self.panic.load(Ordering::Relaxed).is_null() {
+            let nil = ptr::null_mut();
+            let mut err = ManuallyDrop::new(Box::new(err)); // box up the fat ptr
+            let err_ptr: *mut Box<dyn Any + Send + 'static> = &mut **err;
+            if self
+                .panic
+                .compare_exchange(nil, err_ptr, Ordering::Release, Ordering::Relaxed)
+                .is_ok()
+            {
+                // ownership now transferred into self.panic
+            } else {
+                // another panic raced in ahead of us, so drop ours
+                let _: Box<Box<_>> = ManuallyDrop::into_inner(err);
+            }
+        }
+    }
+
+    fn maybe_propagate_panic(&self) {
+        // propagate panic, if any occurred; at this point, all
+        // outstanding jobs have completed, so we can use a relaxed
+        // ordering:
+        let panic = self.panic.swap(ptr::null_mut(), Ordering::Relaxed);
+        if !panic.is_null() {
+            let value = unsafe { Box::from_raw(panic) };
+            unwind::resume_unwinding(*value);
+        }
+    }
+}
+
+impl<'scope> fmt::Debug for Scope<'scope> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("Scope")
+            .field("pool_id", &self.base.registry.id())
+            .field("panic", &self.base.panic)
+            .field("job_completed_latch", &self.base.job_completed_latch)
+            .finish()
+    }
+}
+
+impl<'scope> fmt::Debug for ScopeFifo<'scope> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt.debug_struct("ScopeFifo")
+            .field("num_fifos", &self.fifos.len())
+            .field("pool_id", &self.base.registry.id())
+            .field("panic", &self.base.panic)
+            .field("job_completed_latch", &self.base.job_completed_latch)
+            .finish()
+    }
+}
+
+/// Used to capture a scope `&Self` pointer in jobs, without faking a lifetime.
+///
+/// Unsafe code is still required to dereference the pointer, but that's fine in
+/// scope jobs that are guaranteed to execute before the scope ends.
+struct ScopePtr<T>(*const T);
+
+// SAFETY: !Send for raw pointers is not for safety, just as a lint
+unsafe impl<T: Sync> Send for ScopePtr<T> {}
+
+// SAFETY: !Sync for raw pointers is not for safety, just as a lint
+unsafe impl<T: Sync> Sync for ScopePtr<T> {}
+
+impl<T> ScopePtr<T> {
+    // Helper to avoid disjoint captures of `scope_ptr.0`
+    unsafe fn as_ref(&self) -> &T {
+        &*self.0
+    }
+}