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use crate::job::*;
use crate::registry::Registry;
use crate::unwind;
use std::mem;
use std::sync::Arc;
/// Fires off a task into the Rayon threadpool in the "static" or
/// "global" scope. Just like a standard thread, this task is not
/// tied to the current stack frame, and hence it cannot hold any
/// references other than those with `'static` lifetime. If you want
/// to spawn a task that references stack data, use [the `scope()`
/// function][scope] to create a scope.
///
/// [scope]: fn.scope.html
///
/// Since tasks spawned with this function cannot hold references into
/// the enclosing stack frame, you almost certainly want to use a
/// `move` closure as their argument (otherwise, the closure will
/// typically hold references to any variables from the enclosing
/// function that you happen to use).
///
/// This API assumes that the closure is executed purely for its
/// side-effects (i.e., it might send messages, modify data protected
/// by a mutex, or some such thing).
///
/// There is no guaranteed order of execution for spawns, 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. 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 [`spawn_fifo()`] instead.
///
/// [`spawn_fifo()`]: fn.spawn_fifo.html
///
/// # Panic handling
///
/// If this closure should panic, the resulting panic will be
/// propagated to the panic handler registered in the `ThreadPoolBuilder`,
/// if any. See [`ThreadPoolBuilder::panic_handler()`][ph] for more
/// details.
///
/// [ph]: struct.ThreadPoolBuilder.html#method.panic_handler
///
/// # Examples
///
/// This code creates a Rayon task that increments a global counter.
///
/// ```rust
/// # use rayon_core as rayon;
/// use std::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
///
/// static GLOBAL_COUNTER: AtomicUsize = ATOMIC_USIZE_INIT;
///
/// rayon::spawn(move || {
/// GLOBAL_COUNTER.fetch_add(1, Ordering::SeqCst);
/// });
/// ```
pub fn spawn<F>(func: F)
where
F: FnOnce() + Send + 'static,
{
// We assert that current registry has not terminated.
unsafe { spawn_in(func, &Registry::current()) }
}
/// Spawns an asynchronous job in `registry.`
///
/// Unsafe because `registry` must not yet have terminated.
pub(super) unsafe fn spawn_in<F>(func: F, registry: &Arc<Registry>)
where
F: FnOnce() + Send + 'static,
{
// We assert that this does not hold any references (we know
// this because of the `'static` bound in the interface);
// moreover, we assert that the code below is not supposed to
// be able to panic, and hence the data won't leak but will be
// enqueued into some deque for later execution.
let abort_guard = unwind::AbortIfPanic; // just in case we are wrong, and code CAN panic
let job_ref = spawn_job(func, registry);
registry.inject_or_push(job_ref);
mem::forget(abort_guard);
}
unsafe fn spawn_job<F>(func: F, registry: &Arc<Registry>) -> JobRef
where
F: FnOnce() + Send + 'static,
{
// Ensure that registry cannot terminate until this job has
// executed. This ref is decremented at the (*) below.
registry.increment_terminate_count();
HeapJob::new({
let registry = Arc::clone(registry);
move || {
registry.catch_unwind(func);
registry.terminate(); // (*) permit registry to terminate now
}
})
.into_static_job_ref()
}
/// Fires off a task into the Rayon threadpool in the "static" or
/// "global" scope. Just like a standard thread, this task is not
/// tied to the current stack frame, and hence it cannot hold any
/// references other than those with `'static` lifetime. If you want
/// to spawn a task that references stack data, use [the `scope_fifo()`
/// function](fn.scope_fifo.html) to create a scope.
///
/// The behavior is essentially the same as [the `spawn`
/// function](fn.spawn.html), except that calls from the same thread
/// will be prioritized in FIFO order. This is similar to the now-
/// deprecated [`breadth_first`] option, except the effect is isolated
/// to relative `spawn_fifo` calls, not all threadpool tasks.
///
/// For more details on this design, see Rayon [RFC #1].
///
/// [`breadth_first`]: struct.ThreadPoolBuilder.html#method.breadth_first
///
/// # Panic handling
///
/// If this closure should panic, the resulting panic will be
/// propagated to the panic handler registered in the `ThreadPoolBuilder`,
/// if any. See [`ThreadPoolBuilder::panic_handler()`][ph] for more
/// details.
///
/// [ph]: struct.ThreadPoolBuilder.html#method.panic_handler
pub fn spawn_fifo<F>(func: F)
where
F: FnOnce() + Send + 'static,
{
// We assert that current registry has not terminated.
unsafe { spawn_fifo_in(func, &Registry::current()) }
}
/// Spawns an asynchronous FIFO job in `registry.`
///
/// Unsafe because `registry` must not yet have terminated.
pub(super) unsafe fn spawn_fifo_in<F>(func: F, registry: &Arc<Registry>)
where
F: FnOnce() + Send + 'static,
{
// We assert that this does not hold any references (we know
// this because of the `'static` bound in the interface);
// moreover, we assert that the code below is not supposed to
// be able to panic, and hence the data won't leak but will be
// enqueued into some deque for later execution.
let abort_guard = unwind::AbortIfPanic; // just in case we are wrong, and code CAN panic
let job_ref = spawn_job(func, registry);
// If we're in the pool, use our thread's private fifo for this thread to execute
// in a locally-FIFO order. Otherwise, just use the pool's global injector.
match registry.current_thread() {
Some(worker) => worker.push_fifo(job_ref),
None => registry.inject(job_ref),
}
mem::forget(abort_guard);
}
#[cfg(test)]
mod test;