1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
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
/// [RFC #1]: https://github.com/rayon-rs/rfcs/blob/master/accepted/rfc0001-scope-scheduling.md
///
/// # 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;