| // Copyright 2016 Amanieu d'Antras |
| // |
| // Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or |
| // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or |
| // http://opensource.org/licenses/MIT>, at your option. This file may not be |
| // copied, modified, or distributed except according to those terms. |
| |
| use crate::raw_mutex::RawMutex; |
| use core::num::NonZeroUsize; |
| use lock_api::{self, GetThreadId}; |
| |
| /// Implementation of the `GetThreadId` trait for `lock_api::ReentrantMutex`. |
| pub struct RawThreadId; |
| |
| unsafe impl GetThreadId for RawThreadId { |
| const INIT: RawThreadId = RawThreadId; |
| |
| fn nonzero_thread_id(&self) -> NonZeroUsize { |
| // The address of a thread-local variable is guaranteed to be unique to the |
| // current thread, and is also guaranteed to be non-zero. The variable has to have a |
| // non-zero size to guarantee it has a unique address for each thread. |
| thread_local!(static KEY: u8 = 0); |
| KEY.with(|x| { |
| NonZeroUsize::new(x as *const _ as usize) |
| .expect("thread-local variable address is null") |
| }) |
| } |
| } |
| |
| /// A mutex which can be recursively locked by a single thread. |
| /// |
| /// This type is identical to `Mutex` except for the following points: |
| /// |
| /// - Locking multiple times from the same thread will work correctly instead of |
| /// deadlocking. |
| /// - `ReentrantMutexGuard` does not give mutable references to the locked data. |
| /// Use a `RefCell` if you need this. |
| /// |
| /// See [`Mutex`](type.Mutex.html) for more details about the underlying mutex |
| /// primitive. |
| pub type ReentrantMutex<T> = lock_api::ReentrantMutex<RawMutex, RawThreadId, T>; |
| |
| /// Creates a new reentrant mutex in an unlocked state ready for use. |
| /// |
| /// This allows creating a reentrant mutex in a constant context on stable Rust. |
| pub const fn const_reentrant_mutex<T>(val: T) -> ReentrantMutex<T> { |
| ReentrantMutex::const_new( |
| <RawMutex as lock_api::RawMutex>::INIT, |
| <RawThreadId as lock_api::GetThreadId>::INIT, |
| val, |
| ) |
| } |
| |
| /// An RAII implementation of a "scoped lock" of a reentrant mutex. When this structure |
| /// is dropped (falls out of scope), the lock will be unlocked. |
| /// |
| /// The data protected by the mutex can be accessed through this guard via its |
| /// `Deref` implementation. |
| pub type ReentrantMutexGuard<'a, T> = lock_api::ReentrantMutexGuard<'a, RawMutex, RawThreadId, T>; |
| |
| /// An RAII mutex guard returned by `ReentrantMutexGuard::map`, which can point to a |
| /// subfield of the protected data. |
| /// |
| /// The main difference between `MappedReentrantMutexGuard` and `ReentrantMutexGuard` is that the |
| /// former doesn't support temporarily unlocking and re-locking, since that |
| /// could introduce soundness issues if the locked object is modified by another |
| /// thread. |
| pub type MappedReentrantMutexGuard<'a, T> = |
| lock_api::MappedReentrantMutexGuard<'a, RawMutex, RawThreadId, T>; |
| |
| #[cfg(test)] |
| mod tests { |
| use crate::ReentrantMutex; |
| use std::cell::RefCell; |
| use std::sync::Arc; |
| use std::thread; |
| |
| #[cfg(feature = "serde")] |
| use bincode::{deserialize, serialize}; |
| |
| #[test] |
| fn smoke() { |
| let m = ReentrantMutex::new(2); |
| { |
| let a = m.lock(); |
| { |
| let b = m.lock(); |
| { |
| let c = m.lock(); |
| assert_eq!(*c, 2); |
| } |
| assert_eq!(*b, 2); |
| } |
| assert_eq!(*a, 2); |
| } |
| } |
| |
| #[test] |
| fn is_mutex() { |
| let m = Arc::new(ReentrantMutex::new(RefCell::new(0))); |
| let m2 = m.clone(); |
| let lock = m.lock(); |
| let child = thread::spawn(move || { |
| let lock = m2.lock(); |
| assert_eq!(*lock.borrow(), 4950); |
| }); |
| for i in 0..100 { |
| let lock = m.lock(); |
| *lock.borrow_mut() += i; |
| } |
| drop(lock); |
| child.join().unwrap(); |
| } |
| |
| #[test] |
| fn trylock_works() { |
| let m = Arc::new(ReentrantMutex::new(())); |
| let m2 = m.clone(); |
| let _lock = m.try_lock(); |
| let _lock2 = m.try_lock(); |
| thread::spawn(move || { |
| let lock = m2.try_lock(); |
| assert!(lock.is_none()); |
| }) |
| .join() |
| .unwrap(); |
| let _lock3 = m.try_lock(); |
| } |
| |
| #[test] |
| fn test_reentrant_mutex_debug() { |
| let mutex = ReentrantMutex::new(vec![0u8, 10]); |
| |
| assert_eq!(format!("{:?}", mutex), "ReentrantMutex { data: [0, 10] }"); |
| } |
| |
| #[cfg(feature = "serde")] |
| #[test] |
| fn test_serde() { |
| let contents: Vec<u8> = vec![0, 1, 2]; |
| let mutex = ReentrantMutex::new(contents.clone()); |
| |
| let serialized = serialize(&mutex).unwrap(); |
| let deserialized: ReentrantMutex<Vec<u8>> = deserialize(&serialized).unwrap(); |
| |
| assert_eq!(*(mutex.lock()), *(deserialized.lock())); |
| assert_eq!(contents, *(deserialized.lock())); |
| } |
| } |