vendor/parking_lot_core-0.6.2/src/thread_parker/generic.rs

   1 // Copyright 2016 Amanieu d'Antras
   2 //
   3 // Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
   4 // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
   5 // http://opensource.org/licenses/MIT>, at your option. This file may not be
   6 // copied, modified, or distributed except according to those terms.
   7
   8 //! A simple spin lock based thread parker. Used on platforms without better
   9 //! parking facilities available.
  10
  11 use core::sync::atomic::{spin_loop_hint, AtomicBool, Ordering};
  12 use std::{thread, time::Instant};
  13
  14 // Helper type for putting a thread to sleep until some other thread wakes it up
  15 pub struct ThreadParker {
  16     parked: AtomicBool,
  17 }
  18
  19 impl super::ThreadParkerT for ThreadParker {
  20     type UnparkHandle = UnparkHandle;
  21
  22     const IS_CHEAP_TO_CONSTRUCT: bool = true;
  23
  24     #[inline]
  25     fn new() -> ThreadParker {
  26         ThreadParker {
  27             parked: AtomicBool::new(false),
  28         }
  29     }
  30
  31     #[inline]
  32     unsafe fn prepare_park(&self) {
  33         self.parked.store(true, Ordering::Relaxed);
  34     }
  35
  36     #[inline]
  37     unsafe fn timed_out(&self) -> bool {
  38         self.parked.load(Ordering::Relaxed) != false
  39     }
  40
  41     #[inline]
  42     unsafe fn park(&self) {
  43         while self.parked.load(Ordering::Acquire) != false {
  44             spin_loop_hint();
  45         }
  46     }
  47
  48     #[inline]
  49     unsafe fn park_until(&self, timeout: Instant) -> bool {
  50         while self.parked.load(Ordering::Acquire) != false {
  51             if Instant::now() >= timeout {
  52                 return false;
  53             }
  54             spin_loop_hint();
  55         }
  56         true
  57     }
  58
  59     #[inline]
  60     unsafe fn unpark_lock(&self) -> UnparkHandle {
  61         // We don't need to lock anything, just clear the state
  62         self.parked.store(false, Ordering::Release);
  63         UnparkHandle(())
  64     }
  65 }
  66
  67 pub struct UnparkHandle(());
  68
  69 impl super::UnparkHandleT for UnparkHandle {
  70     #[inline]
  71     unsafe fn unpark(self) {}
  72 }
  73
  74 #[inline]
  75 pub fn thread_yield() {
  76     thread::yield_now();
  77 }