| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License.. |
| |
| //! Generic support for building blocking abstractions. |
| |
| use crate::mem; |
| use crate::sync::atomic::{AtomicBool, Ordering}; |
| use crate::sync::Arc; |
| use crate::thread::{self, SgxThread as Thread}; |
| use crate::time::Instant; |
| #[cfg(not(feature = "untrusted_time"))] |
| use crate::untrusted::time::InstantEx; |
| |
| struct Inner { |
| thread: Thread, |
| woken: AtomicBool, |
| } |
| |
| unsafe impl Send for Inner {} |
| unsafe impl Sync for Inner {} |
| |
| #[derive(Clone)] |
| pub struct SignalToken { |
| inner: Arc<Inner>, |
| } |
| |
| pub struct WaitToken { |
| inner: Arc<Inner>, |
| } |
| |
| impl !Send for WaitToken {} |
| |
| impl !Sync for WaitToken {} |
| |
| pub fn tokens() -> (WaitToken, SignalToken) { |
| let inner = Arc::new(Inner { thread: thread::current(), woken: AtomicBool::new(false) }); |
| let wait_token = WaitToken { inner: inner.clone() }; |
| let signal_token = SignalToken { inner }; |
| (wait_token, signal_token) |
| } |
| |
| impl SignalToken { |
| pub fn signal(&self) -> bool { |
| let wake = self |
| .inner |
| .woken |
| .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst) |
| .is_ok(); |
| if wake { |
| self.inner.thread.unpark(); |
| } |
| wake |
| } |
| |
| /// Converts to an unsafe usize value. Useful for storing in a pipe's state |
| /// flag. |
| #[inline] |
| pub unsafe fn cast_to_usize(self) -> usize { |
| mem::transmute(self.inner) |
| } |
| |
| /// Converts from an unsafe usize value. Useful for retrieving a pipe's state |
| /// flag. |
| #[inline] |
| pub unsafe fn cast_from_usize(signal_ptr: usize) -> SignalToken { |
| SignalToken { inner: mem::transmute(signal_ptr) } |
| } |
| } |
| |
| impl WaitToken { |
| pub fn wait(self) { |
| while !self.inner.woken.load(Ordering::SeqCst) { |
| thread::park() |
| } |
| } |
| |
| /// Returns `true` if we wake up normally. |
| pub fn wait_max_until(self, end: Instant) -> bool { |
| while !self.inner.woken.load(Ordering::SeqCst) { |
| let now = Instant::now(); |
| if now >= end { |
| return false; |
| } |
| thread::park_timeout(end - now) |
| } |
| true |
| } |
| } |