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};
86