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 //! This library exposes a low-level API for creating your own efficient 9 //! synchronization primitives. 10 //! 11 //! # The parking lot 12 //! 13 //! To keep synchronization primitives small, all thread queuing and suspending 14 //! functionality is offloaded to the *parking lot*. The idea behind this is based 15 //! on the Webkit [`WTF::ParkingLot`](https://webkit.org/blog/6161/locking-in-webkit/) 16 //! class, which essentially consists of a hash table mapping of lock addresses 17 //! to queues of parked (sleeping) threads. The Webkit parking lot was itself 18 //! inspired by Linux [futexes](http://man7.org/linux/man-pages/man2/futex.2.html), 19 //! but it is more powerful since it allows invoking callbacks while holding a 20 //! queue lock. 21 //! 22 //! There are two main operations that can be performed on the parking lot: 23 //! 24 //! - *Parking* refers to suspending the thread while simultaneously enqueuing it 25 //! on a queue keyed by some address. 26 //! - *Unparking* refers to dequeuing a thread from a queue keyed by some address 27 //! and resuming it. 28 //! 29 //! See the documentation of the individual functions for more details. 30 //! 31 //! # Building custom synchronization primitives 32 //! 33 //! Building custom synchronization primitives is very simple since the parking 34 //! lot takes care of all the hard parts for you. A simple example for a 35 //! custom primitive would be to integrate a `Mutex` inside another data type. 36 //! Since a mutex only requires 2 bits, it can share space with other data. 37 //! For example, one could create an `ArcMutex` type that combines the atomic 38 //! reference count and the two mutex bits in the same atomic word. 39 40 #![warn(missing_docs)] 41 #![warn(rust_2018_idioms)] 42 #![cfg_attr( 43 all(target_env = "sgx", target_vendor = "fortanix"), 44 feature(sgx_platform) 45 )] 46 #![cfg_attr( 47 all( 48 feature = "nightly", 49 target_arch = "wasm32", 50 target_feature = "atomics" 51 ), 52 feature(stdsimd) 53 )] 54 55 mod parking_lot; 56 mod spinwait; 57 mod thread_parker; 58 mod util; 59 mod word_lock; 60 61 pub use self::parking_lot::deadlock; 62 pub use self::parking_lot::{park, unpark_all, unpark_filter, unpark_one, unpark_requeue}; 63 pub use self::parking_lot::{ 64 FilterOp, ParkResult, ParkToken, RequeueOp, UnparkResult, UnparkToken, 65 }; 66 pub use self::parking_lot::{DEFAULT_PARK_TOKEN, DEFAULT_UNPARK_TOKEN}; 67 pub use self::spinwait::SpinWait; 68