crossbeam_epoch/
default.rs

1//! The default garbage collector.
2//!
3//! For each thread, a participant is lazily initialized on its first use, when the current thread
4//! is registered in the default collector.  If initialized, the thread's participant will get
5//! destructed on thread exit, which in turn unregisters the thread.
6
7use crate::collector::{Collector, LocalHandle};
8use crate::guard::Guard;
9use crate::primitive::thread_local;
10#[cfg(not(crossbeam_loom))]
11use once_cell::sync::Lazy;
12
13/// The global data for the default garbage collector.
14#[cfg(not(crossbeam_loom))]
15static COLLECTOR: Lazy<Collector> = Lazy::new(Collector::new);
16// FIXME: loom does not currently provide the equivalent of Lazy:
17// https://github.com/tokio-rs/loom/issues/263
18#[cfg(crossbeam_loom)]
19loom::lazy_static! {
20    /// The global data for the default garbage collector.
21    static ref COLLECTOR: Collector = Collector::new();
22}
23
24thread_local! {
25    /// The per-thread participant for the default garbage collector.
26    static HANDLE: LocalHandle = COLLECTOR.register();
27}
28
29/// Pins the current thread.
30#[inline]
31pub fn pin() -> Guard {
32    with_handle(|handle| handle.pin())
33}
34
35/// Returns `true` if the current thread is pinned.
36#[inline]
37pub fn is_pinned() -> bool {
38    with_handle(|handle| handle.is_pinned())
39}
40
41/// Returns the default global collector.
42pub fn default_collector() -> &'static Collector {
43    &COLLECTOR
44}
45
46#[inline]
47fn with_handle<F, R>(mut f: F) -> R
48where
49    F: FnMut(&LocalHandle) -> R,
50{
51    HANDLE
52        .try_with(|h| f(h))
53        .unwrap_or_else(|_| f(&COLLECTOR.register()))
54}
55
56#[cfg(all(test, not(crossbeam_loom)))]
57mod tests {
58    use crossbeam_utils::thread;
59
60    #[test]
61    fn pin_while_exiting() {
62        struct Foo;
63
64        impl Drop for Foo {
65            fn drop(&mut self) {
66                // Pin after `HANDLE` has been dropped. This must not panic.
67                super::pin();
68            }
69        }
70
71        thread_local! {
72            static FOO: Foo = Foo;
73        }
74
75        thread::scope(|scope| {
76            scope.spawn(|_| {
77                // Initialize `FOO` and then `HANDLE`.
78                FOO.with(|_| ());
79                super::pin();
80                // At thread exit, `HANDLE` gets dropped first and `FOO` second.
81            });
82        })
83        .unwrap();
84    }
85}
crossbeam_epoch/default.rs

crossbeam_epoch/
default.rs
