1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10 #![unstable(feature = "reentrant_mutex", reason = "new API")]
17 use sys_common::poison::{self, TryLockError, TryLockResult, LockResult};
18 use sys::mutex as sys;
20 /// A re-entrant mutual exclusion
22 /// This mutex will block *other* threads waiting for the lock to become available. The thread
23 /// which has already locked the mutex can lock it multiple times without blocking, preventing a
24 /// common source of deadlocks.
25 pub struct ReentrantMutex<T> {
26 inner: Box<sys::ReentrantMutex>,
31 unsafe impl<T: Send> Send for ReentrantMutex<T> {}
32 unsafe impl<T: Send> Sync for ReentrantMutex<T> {}
35 /// An RAII implementation of a "scoped lock" of a mutex. When this structure is
36 /// dropped (falls out of scope), the lock will be unlocked.
38 /// The data protected by the mutex can be accessed through this guard via its
39 /// Deref and DerefMut implementations
41 pub struct ReentrantMutexGuard<'a, T: 'a> {
42 // funny underscores due to how Deref/DerefMut currently work (they
43 // disregard field privacy).
44 __lock: &'a ReentrantMutex<T>,
45 __poison: poison::Guard,
48 impl<'a, T> !marker::Send for ReentrantMutexGuard<'a, T> {}
51 impl<T> ReentrantMutex<T> {
52 /// Creates a new reentrant mutex in an unlocked state.
53 pub fn new(t: T) -> ReentrantMutex<T> {
55 inner: box unsafe { sys::ReentrantMutex::new() },
56 poison: poison::FLAG_INIT,
61 /// Acquires a mutex, blocking the current thread until it is able to do so.
63 /// This function will block the caller until it is available to acquire the mutex.
64 /// Upon returning, the thread is the only thread with the mutex held. When the thread
65 /// calling this method already holds the lock, the call shall succeed without
70 /// If another user of this mutex panicked while holding the mutex, then
71 /// this call will return failure if the mutex would otherwise be
73 pub fn lock(&self) -> LockResult<ReentrantMutexGuard<T>> {
74 unsafe { self.inner.lock() }
75 ReentrantMutexGuard::new(&self)
78 /// Attempts to acquire this lock.
80 /// If the lock could not be acquired at this time, then `Err` is returned.
81 /// Otherwise, an RAII guard is returned.
83 /// This function does not block.
87 /// If another user of this mutex panicked while holding the mutex, then
88 /// this call will return failure if the mutex would otherwise be
90 pub fn try_lock(&self) -> TryLockResult<ReentrantMutexGuard<T>> {
91 if unsafe { self.inner.try_lock() } {
92 Ok(try!(ReentrantMutexGuard::new(&self)))
94 Err(TryLockError::WouldBlock)
100 impl<T> Drop for ReentrantMutex<T> {
102 // This is actually safe b/c we know that there is no further usage of
103 // this mutex (it's up to the user to arrange for a mutex to get
104 // dropped, that's not our job)
105 unsafe { self.inner.destroy() }
109 impl<T: fmt::Debug + 'static> fmt::Debug for ReentrantMutex<T> {
110 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
111 match self.try_lock() {
112 Ok(guard) => write!(f, "ReentrantMutex {{ data: {:?} }}", &*guard),
113 Err(TryLockError::Poisoned(err)) => {
114 write!(f, "ReentrantMutex {{ data: Poisoned({:?}) }}", &**err.get_ref())
116 Err(TryLockError::WouldBlock) => write!(f, "ReentrantMutex {{ <locked> }}")
121 impl<'mutex, T> ReentrantMutexGuard<'mutex, T> {
122 fn new(lock: &'mutex ReentrantMutex<T>)
123 -> LockResult<ReentrantMutexGuard<'mutex, T>> {
124 poison::map_result(lock.poison.borrow(), |guard| {
125 ReentrantMutexGuard {
133 impl<'mutex, T> Deref for ReentrantMutexGuard<'mutex, T> {
136 fn deref<'a>(&'a self) -> &'a T {
142 impl<'a, T> Drop for ReentrantMutexGuard<'a, T> {
146 self.__lock.poison.done(&self.__poison);
147 self.__lock.inner.unlock();
156 use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
164 let m = ReentrantMutex::new(());
166 let a = m.lock().unwrap();
168 let b = m.lock().unwrap();
170 let c = m.lock().unwrap();
181 let m = ReentrantMutex::new(RefCell::new(0));
182 let lock = m.lock().unwrap();
183 let handle = thread::scoped(|| {
184 let lock = m.lock().unwrap();
185 assert_eq!(*lock.borrow(), 4950);
188 let mut lock = m.lock().unwrap();
189 *lock.borrow_mut() += i;
197 let m = ReentrantMutex::new(());
198 let lock = m.try_lock().unwrap();
199 let lock2 = m.try_lock().unwrap();
202 let lock = m.try_lock();
203 assert!(lock.is_err());
206 let lock3 = m.try_lock().unwrap();
209 pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>);
210 impl<'a> Drop for Answer<'a> {
212 *self.0.borrow_mut() = 42;
218 let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
220 let result = thread::spawn(move ||{
221 let lock = mc.lock().unwrap();
222 *lock.borrow_mut() = 1;
223 let lock2 = mc.lock().unwrap();
224 *lock.borrow_mut() = 2;
225 let answer = Answer(lock2);
226 panic!("What the answer to my lifetimes dilemma is?");
229 assert!(result.is_err());
230 let r = m.lock().err().unwrap().into_inner();
231 assert_eq!(*r.borrow(), 42);