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