parking_lot_core/thread_parker/
mod.rs

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1use cfg_if::cfg_if;
2use std::time::Instant;
3
4/// Trait for the platform thread parker implementation.
5///
6/// All unsafe methods are unsafe because the Unix thread parker is based on
7/// pthread mutexes and condvars. Those primitives must not be moved and used
8/// from any other memory address than the one they were located at when they
9/// were initialized. As such, it's UB to call any unsafe method on
10/// `ThreadParkerT` if the implementing instance has moved since the last
11/// call to any of the unsafe methods.
12pub trait ThreadParkerT {
13    type UnparkHandle: UnparkHandleT;
14
15    const IS_CHEAP_TO_CONSTRUCT: bool;
16
17    fn new() -> Self;
18
19    /// Prepares the parker. This should be called before adding it to the queue.
20    unsafe fn prepare_park(&self);
21
22    /// Checks if the park timed out. This should be called while holding the
23    /// queue lock after park_until has returned false.
24    unsafe fn timed_out(&self) -> bool;
25
26    /// Parks the thread until it is unparked. This should be called after it has
27    /// been added to the queue, after unlocking the queue.
28    unsafe fn park(&self);
29
30    /// Parks the thread until it is unparked or the timeout is reached. This
31    /// should be called after it has been added to the queue, after unlocking
32    /// the queue. Returns true if we were unparked and false if we timed out.
33    unsafe fn park_until(&self, timeout: Instant) -> bool;
34
35    /// Locks the parker to prevent the target thread from exiting. This is
36    /// necessary to ensure that thread-local ThreadData objects remain valid.
37    /// This should be called while holding the queue lock.
38    unsafe fn unpark_lock(&self) -> Self::UnparkHandle;
39}
40
41/// Handle for a thread that is about to be unparked. We need to mark the thread
42/// as unparked while holding the queue lock, but we delay the actual unparking
43/// until after the queue lock is released.
44pub trait UnparkHandleT {
45    /// Wakes up the parked thread. This should be called after the queue lock is
46    /// released to avoid blocking the queue for too long.
47    ///
48    /// This method is unsafe for the same reason as the unsafe methods in
49    /// `ThreadParkerT`.
50    unsafe fn unpark(self);
51}
52
53cfg_if! {
54    if #[cfg(any(target_os = "linux", target_os = "android"))] {
55        #[path = "linux.rs"]
56        mod imp;
57    } else if #[cfg(unix)] {
58        #[path = "unix.rs"]
59        mod imp;
60    } else if #[cfg(windows)] {
61        #[path = "windows/mod.rs"]
62        mod imp;
63    } else if #[cfg(target_os = "redox")] {
64        #[path = "redox.rs"]
65        mod imp;
66    } else if #[cfg(all(target_env = "sgx", target_vendor = "fortanix"))] {
67        #[path = "sgx.rs"]
68        mod imp;
69    } else if #[cfg(all(
70        feature = "nightly",
71        target_family = "wasm",
72        target_feature = "atomics"
73    ))] {
74        #[path = "wasm_atomic.rs"]
75        mod imp;
76    } else if #[cfg(target_family = "wasm")] {
77        #[path = "wasm.rs"]
78        mod imp;
79    } else {
80        #[path = "generic.rs"]
81        mod imp;
82    }
83}
84
85pub use self::imp::{thread_yield, ThreadParker, UnparkHandle};
parking_lot_core/thread_parker/mod.rs

parking_lot_core/thread_parker/
mod.rs
