2f703e4304
These were found by running tidy on stable versions of rust and finding features stabilised with the wrong version numbers.
681 lines
22 KiB
Rust
681 lines
22 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use cell::UnsafeCell;
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use fmt;
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use mem;
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use ops::{Deref, DerefMut};
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use ptr;
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use sys_common::mutex as sys;
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use sys_common::poison::{self, TryLockError, TryLockResult, LockResult};
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/// A mutual exclusion primitive useful for protecting shared data
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///
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/// This mutex will block threads waiting for the lock to become available. The
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/// mutex can also be statically initialized or created via a `new`
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/// constructor. Each mutex has a type parameter which represents the data that
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/// it is protecting. The data can only be accessed through the RAII guards
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/// returned from `lock` and `try_lock`, which guarantees that the data is only
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/// ever accessed when the mutex is locked.
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///
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/// # Poisoning
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///
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/// The mutexes in this module implement a strategy called "poisoning" where a
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/// mutex is considered poisoned whenever a thread panics while holding the
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/// mutex. Once a mutex is poisoned, all other threads are unable to access the
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/// data by default as it is likely tainted (some invariant is not being
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/// upheld).
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///
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/// For a mutex, this means that the `lock` and `try_lock` methods return a
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/// `Result` which indicates whether a mutex has been poisoned or not. Most
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/// usage of a mutex will simply `unwrap()` these results, propagating panics
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/// among threads to ensure that a possibly invalid invariant is not witnessed.
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///
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/// A poisoned mutex, however, does not prevent all access to the underlying
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/// data. The `PoisonError` type has an `into_inner` method which will return
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/// the guard that would have otherwise been returned on a successful lock. This
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/// allows access to the data, despite the lock being poisoned.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::{Arc, Mutex};
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/// use std::thread;
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/// use std::sync::mpsc::channel;
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///
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/// const N: usize = 10;
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///
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/// // Spawn a few threads to increment a shared variable (non-atomically), and
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/// // let the main thread know once all increments are done.
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/// //
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/// // Here we're using an Arc to share memory among threads, and the data inside
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/// // the Arc is protected with a mutex.
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/// let data = Arc::new(Mutex::new(0));
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///
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/// let (tx, rx) = channel();
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/// for _ in 0..N {
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/// let (data, tx) = (data.clone(), tx.clone());
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/// thread::spawn(move || {
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/// // The shared state can only be accessed once the lock is held.
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/// // Our non-atomic increment is safe because we're the only thread
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/// // which can access the shared state when the lock is held.
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/// //
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/// // We unwrap() the return value to assert that we are not expecting
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/// // threads to ever fail while holding the lock.
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/// let mut data = data.lock().unwrap();
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/// *data += 1;
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/// if *data == N {
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/// tx.send(()).unwrap();
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/// }
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/// // the lock is unlocked here when `data` goes out of scope.
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/// });
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/// }
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///
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/// rx.recv().unwrap();
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/// ```
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///
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/// To recover from a poisoned mutex:
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///
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/// ```
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/// use std::sync::{Arc, Mutex};
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/// use std::thread;
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///
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/// let lock = Arc::new(Mutex::new(0_u32));
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/// let lock2 = lock.clone();
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///
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/// let _ = thread::spawn(move || -> () {
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/// // This thread will acquire the mutex first, unwrapping the result of
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/// // `lock` because the lock has not been poisoned.
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/// let _guard = lock2.lock().unwrap();
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///
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/// // This panic while holding the lock (`_guard` is in scope) will poison
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/// // the mutex.
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/// panic!();
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/// }).join();
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///
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/// // The lock is poisoned by this point, but the returned result can be
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/// // pattern matched on to return the underlying guard on both branches.
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/// let mut guard = match lock.lock() {
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/// Ok(guard) => guard,
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/// Err(poisoned) => poisoned.into_inner(),
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/// };
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///
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/// *guard += 1;
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct Mutex<T: ?Sized> {
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// Note that this mutex is in a *box*, not inlined into the struct itself.
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// Once a native mutex has been used once, its address can never change (it
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// can't be moved). This mutex type can be safely moved at any time, so to
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// ensure that the native mutex is used correctly we box the inner mutex to
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// give it a constant address.
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inner: Box<sys::Mutex>,
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poison: poison::Flag,
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data: UnsafeCell<T>,
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}
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// these are the only places where `T: Send` matters; all other
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// functionality works fine on a single thread.
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: ?Sized + Send> Send for Mutex<T> { }
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: ?Sized + Send> Sync for Mutex<T> { }
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/// An RAII implementation of a "scoped lock" of a mutex. When this structure is
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/// dropped (falls out of scope), the lock will be unlocked.
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///
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/// The data protected by the mutex can be accessed through this guard via its
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/// [`Deref`] and [`DerefMut`] implementations.
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///
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/// This structure is created by the [`lock`] and [`try_lock`] methods on
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/// [`Mutex`].
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///
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/// [`Deref`]: ../../std/ops/trait.Deref.html
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/// [`DerefMut`]: ../../std/ops/trait.DerefMut.html
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/// [`lock`]: struct.Mutex.html#method.lock
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/// [`try_lock`]: struct.Mutex.html#method.try_lock
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/// [`Mutex`]: struct.Mutex.html
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#[must_use]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct MutexGuard<'a, T: ?Sized + 'a> {
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// funny underscores due to how Deref/DerefMut currently work (they
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// disregard field privacy).
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__lock: &'a Mutex<T>,
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__poison: poison::Guard,
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, T: ?Sized> !Send for MutexGuard<'a, T> { }
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#[stable(feature = "mutexguard", since = "1.19.0")]
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unsafe impl<'a, T: ?Sized + Sync> Sync for MutexGuard<'a, T> { }
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impl<T> Mutex<T> {
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/// Creates a new mutex in an unlocked state ready for use.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::Mutex;
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///
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/// let mutex = Mutex::new(0);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn new(t: T) -> Mutex<T> {
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let mut m = Mutex {
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inner: box sys::Mutex::new(),
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poison: poison::Flag::new(),
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data: UnsafeCell::new(t),
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};
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unsafe {
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m.inner.init();
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}
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m
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}
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}
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impl<T: ?Sized> Mutex<T> {
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/// Acquires a mutex, blocking the current thread until it is able to do so.
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///
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/// This function will block the local thread until it is available to acquire
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/// the mutex. Upon returning, the thread is the only thread with the lock
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/// held. An RAII guard is returned to allow scoped unlock of the lock. When
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/// the guard goes out of scope, the mutex will be unlocked.
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///
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/// The exact behavior on locking a mutex in the thread which already holds
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/// the lock is left unspecified. However, this function will not return on
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/// the second call (it might panic or deadlock, for example).
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///
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/// # Errors
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///
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/// If another user of this mutex panicked while holding the mutex, then
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/// this call will return an error once the mutex is acquired.
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///
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/// # Panics
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///
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/// This function might panic when called if the lock is already held by
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/// the current thread.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::{Arc, Mutex};
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/// use std::thread;
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///
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/// let mutex = Arc::new(Mutex::new(0));
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/// let c_mutex = mutex.clone();
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///
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/// thread::spawn(move || {
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/// *c_mutex.lock().unwrap() = 10;
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/// }).join().expect("thread::spawn failed");
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/// assert_eq!(*mutex.lock().unwrap(), 10);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn lock(&self) -> LockResult<MutexGuard<T>> {
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unsafe {
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self.inner.lock();
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MutexGuard::new(self)
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}
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}
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/// Attempts to acquire this lock.
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///
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/// If the lock could not be acquired at this time, then `Err` is returned.
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/// Otherwise, an RAII guard is returned. The lock will be unlocked when the
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/// guard is dropped.
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///
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/// This function does not block.
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///
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/// # Errors
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///
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/// If another user of this mutex panicked while holding the mutex, then
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/// this call will return failure if the mutex would otherwise be
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/// acquired.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::{Arc, Mutex};
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/// use std::thread;
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///
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/// let mutex = Arc::new(Mutex::new(0));
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/// let c_mutex = mutex.clone();
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///
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/// thread::spawn(move || {
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/// let mut lock = c_mutex.try_lock();
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/// if let Ok(ref mut mutex) = lock {
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/// **mutex = 10;
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/// } else {
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/// println!("try_lock failed");
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/// }
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/// }).join().expect("thread::spawn failed");
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/// assert_eq!(*mutex.lock().unwrap(), 10);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub fn try_lock(&self) -> TryLockResult<MutexGuard<T>> {
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unsafe {
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if self.inner.try_lock() {
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Ok(MutexGuard::new(self)?)
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} else {
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Err(TryLockError::WouldBlock)
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}
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}
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}
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/// Determines whether the mutex is poisoned.
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///
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/// If another thread is active, the mutex can still become poisoned at any
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/// time. You should not trust a `false` value for program correctness
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/// without additional synchronization.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::{Arc, Mutex};
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/// use std::thread;
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///
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/// let mutex = Arc::new(Mutex::new(0));
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/// let c_mutex = mutex.clone();
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///
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/// let _ = thread::spawn(move || {
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/// let _lock = c_mutex.lock().unwrap();
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/// panic!(); // the mutex gets poisoned
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/// }).join();
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/// assert_eq!(mutex.is_poisoned(), true);
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/// ```
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#[inline]
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#[stable(feature = "sync_poison", since = "1.2.0")]
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pub fn is_poisoned(&self) -> bool {
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self.poison.get()
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}
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/// Consumes this mutex, returning the underlying data.
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///
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/// # Errors
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///
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/// If another user of this mutex panicked while holding the mutex, then
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/// this call will return an error instead.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::Mutex;
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///
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/// let mutex = Mutex::new(0);
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/// assert_eq!(mutex.into_inner().unwrap(), 0);
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/// ```
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#[stable(feature = "mutex_into_inner", since = "1.6.0")]
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pub fn into_inner(self) -> LockResult<T> where T: Sized {
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// We know statically that there are no outstanding references to
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// `self` so there's no need to lock the inner mutex.
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//
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// To get the inner value, we'd like to call `data.into_inner()`,
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// but because `Mutex` impl-s `Drop`, we can't move out of it, so
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// we'll have to destructure it manually instead.
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unsafe {
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// Like `let Mutex { inner, poison, data } = self`.
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let (inner, poison, data) = {
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let Mutex { ref inner, ref poison, ref data } = self;
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(ptr::read(inner), ptr::read(poison), ptr::read(data))
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};
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mem::forget(self);
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inner.destroy(); // Keep in sync with the `Drop` impl.
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drop(inner);
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poison::map_result(poison.borrow(), |_| data.into_inner())
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}
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}
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/// Returns a mutable reference to the underlying data.
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///
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/// Since this call borrows the `Mutex` mutably, no actual locking needs to
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/// take place---the mutable borrow statically guarantees no locks exist.
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///
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/// # Errors
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///
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/// If another user of this mutex panicked while holding the mutex, then
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/// this call will return an error instead.
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///
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/// # Examples
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///
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/// ```
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/// use std::sync::Mutex;
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///
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/// let mut mutex = Mutex::new(0);
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/// *mutex.get_mut().unwrap() = 10;
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/// assert_eq!(*mutex.lock().unwrap(), 10);
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/// ```
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#[stable(feature = "mutex_get_mut", since = "1.6.0")]
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pub fn get_mut(&mut self) -> LockResult<&mut T> {
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// We know statically that there are no other references to `self`, so
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// there's no need to lock the inner mutex.
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let data = unsafe { &mut *self.data.get() };
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poison::map_result(self.poison.borrow(), |_| data )
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<#[may_dangle] T: ?Sized> Drop for Mutex<T> {
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fn drop(&mut self) {
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// This is actually safe b/c we know that there is no further usage of
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// this mutex (it's up to the user to arrange for a mutex to get
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// dropped, that's not our job)
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//
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// IMPORTANT: This code must be kept in sync with `Mutex::into_inner`.
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unsafe { self.inner.destroy() }
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}
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}
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#[stable(feature = "mutex_default", since = "1.10.0")]
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impl<T: ?Sized + Default> Default for Mutex<T> {
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/// Creates a `Mutex<T>`, with the `Default` value for T.
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fn default() -> Mutex<T> {
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Mutex::new(Default::default())
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T: ?Sized + fmt::Debug> fmt::Debug for Mutex<T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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match self.try_lock() {
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Ok(guard) => write!(f, "Mutex {{ data: {:?} }}", &*guard),
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Err(TryLockError::Poisoned(err)) => {
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write!(f, "Mutex {{ data: Poisoned({:?}) }}", &**err.get_ref())
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},
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Err(TryLockError::WouldBlock) => write!(f, "Mutex {{ <locked> }}")
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}
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}
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}
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impl<'mutex, T: ?Sized> MutexGuard<'mutex, T> {
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unsafe fn new(lock: &'mutex Mutex<T>) -> LockResult<MutexGuard<'mutex, T>> {
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poison::map_result(lock.poison.borrow(), |guard| {
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MutexGuard {
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__lock: lock,
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__poison: guard,
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}
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})
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'mutex, T: ?Sized> Deref for MutexGuard<'mutex, T> {
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type Target = T;
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fn deref(&self) -> &T {
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unsafe { &*self.__lock.data.get() }
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'mutex, T: ?Sized> DerefMut for MutexGuard<'mutex, T> {
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fn deref_mut(&mut self) -> &mut T {
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unsafe { &mut *self.__lock.data.get() }
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, T: ?Sized> Drop for MutexGuard<'a, T> {
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#[inline]
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fn drop(&mut self) {
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unsafe {
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self.__lock.poison.done(&self.__poison);
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self.__lock.inner.unlock();
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}
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}
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}
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#[stable(feature = "std_debug", since = "1.16.0")]
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impl<'a, T: ?Sized + fmt::Debug> fmt::Debug for MutexGuard<'a, T> {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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f.debug_struct("MutexGuard")
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.field("lock", &self.__lock)
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.finish()
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}
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}
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pub fn guard_lock<'a, T: ?Sized>(guard: &MutexGuard<'a, T>) -> &'a sys::Mutex {
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&guard.__lock.inner
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}
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pub fn guard_poison<'a, T: ?Sized>(guard: &MutexGuard<'a, T>) -> &'a poison::Flag {
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&guard.__lock.poison
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}
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#[cfg(all(test, not(target_os = "emscripten")))]
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mod tests {
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use sync::mpsc::channel;
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use sync::{Arc, Mutex, Condvar};
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use sync::atomic::{AtomicUsize, Ordering};
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use thread;
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struct Packet<T>(Arc<(Mutex<T>, Condvar)>);
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#[derive(Eq, PartialEq, Debug)]
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struct NonCopy(i32);
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#[test]
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fn smoke() {
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let m = Mutex::new(());
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drop(m.lock().unwrap());
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drop(m.lock().unwrap());
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}
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#[test]
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fn lots_and_lots() {
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const J: u32 = 1000;
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const K: u32 = 3;
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let m = Arc::new(Mutex::new(0));
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fn inc(m: &Mutex<u32>) {
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for _ in 0..J {
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*m.lock().unwrap() += 1;
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}
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}
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let (tx, rx) = channel();
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for _ in 0..K {
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|
let tx2 = tx.clone();
|
|
let m2 = m.clone();
|
|
thread::spawn(move|| { inc(&m2); tx2.send(()).unwrap(); });
|
|
let tx2 = tx.clone();
|
|
let m2 = m.clone();
|
|
thread::spawn(move|| { inc(&m2); tx2.send(()).unwrap(); });
|
|
}
|
|
|
|
drop(tx);
|
|
for _ in 0..2 * K {
|
|
rx.recv().unwrap();
|
|
}
|
|
assert_eq!(*m.lock().unwrap(), J * K * 2);
|
|
}
|
|
|
|
#[test]
|
|
fn try_lock() {
|
|
let m = Mutex::new(());
|
|
*m.try_lock().unwrap() = ();
|
|
}
|
|
|
|
#[test]
|
|
fn test_into_inner() {
|
|
let m = Mutex::new(NonCopy(10));
|
|
assert_eq!(m.into_inner().unwrap(), NonCopy(10));
|
|
}
|
|
|
|
#[test]
|
|
fn test_into_inner_drop() {
|
|
struct Foo(Arc<AtomicUsize>);
|
|
impl Drop for Foo {
|
|
fn drop(&mut self) {
|
|
self.0.fetch_add(1, Ordering::SeqCst);
|
|
}
|
|
}
|
|
let num_drops = Arc::new(AtomicUsize::new(0));
|
|
let m = Mutex::new(Foo(num_drops.clone()));
|
|
assert_eq!(num_drops.load(Ordering::SeqCst), 0);
|
|
{
|
|
let _inner = m.into_inner().unwrap();
|
|
assert_eq!(num_drops.load(Ordering::SeqCst), 0);
|
|
}
|
|
assert_eq!(num_drops.load(Ordering::SeqCst), 1);
|
|
}
|
|
|
|
#[test]
|
|
fn test_into_inner_poison() {
|
|
let m = Arc::new(Mutex::new(NonCopy(10)));
|
|
let m2 = m.clone();
|
|
let _ = thread::spawn(move || {
|
|
let _lock = m2.lock().unwrap();
|
|
panic!("test panic in inner thread to poison mutex");
|
|
}).join();
|
|
|
|
assert!(m.is_poisoned());
|
|
match Arc::try_unwrap(m).unwrap().into_inner() {
|
|
Err(e) => assert_eq!(e.into_inner(), NonCopy(10)),
|
|
Ok(x) => panic!("into_inner of poisoned Mutex is Ok: {:?}", x),
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_get_mut() {
|
|
let mut m = Mutex::new(NonCopy(10));
|
|
*m.get_mut().unwrap() = NonCopy(20);
|
|
assert_eq!(m.into_inner().unwrap(), NonCopy(20));
|
|
}
|
|
|
|
#[test]
|
|
fn test_get_mut_poison() {
|
|
let m = Arc::new(Mutex::new(NonCopy(10)));
|
|
let m2 = m.clone();
|
|
let _ = thread::spawn(move || {
|
|
let _lock = m2.lock().unwrap();
|
|
panic!("test panic in inner thread to poison mutex");
|
|
}).join();
|
|
|
|
assert!(m.is_poisoned());
|
|
match Arc::try_unwrap(m).unwrap().get_mut() {
|
|
Err(e) => assert_eq!(*e.into_inner(), NonCopy(10)),
|
|
Ok(x) => panic!("get_mut of poisoned Mutex is Ok: {:?}", x),
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_mutex_arc_condvar() {
|
|
let packet = Packet(Arc::new((Mutex::new(false), Condvar::new())));
|
|
let packet2 = Packet(packet.0.clone());
|
|
let (tx, rx) = channel();
|
|
let _t = thread::spawn(move|| {
|
|
// wait until parent gets in
|
|
rx.recv().unwrap();
|
|
let &(ref lock, ref cvar) = &*packet2.0;
|
|
let mut lock = lock.lock().unwrap();
|
|
*lock = true;
|
|
cvar.notify_one();
|
|
});
|
|
|
|
let &(ref lock, ref cvar) = &*packet.0;
|
|
let mut lock = lock.lock().unwrap();
|
|
tx.send(()).unwrap();
|
|
assert!(!*lock);
|
|
while !*lock {
|
|
lock = cvar.wait(lock).unwrap();
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_arc_condvar_poison() {
|
|
let packet = Packet(Arc::new((Mutex::new(1), Condvar::new())));
|
|
let packet2 = Packet(packet.0.clone());
|
|
let (tx, rx) = channel();
|
|
|
|
let _t = thread::spawn(move || -> () {
|
|
rx.recv().unwrap();
|
|
let &(ref lock, ref cvar) = &*packet2.0;
|
|
let _g = lock.lock().unwrap();
|
|
cvar.notify_one();
|
|
// Parent should fail when it wakes up.
|
|
panic!();
|
|
});
|
|
|
|
let &(ref lock, ref cvar) = &*packet.0;
|
|
let mut lock = lock.lock().unwrap();
|
|
tx.send(()).unwrap();
|
|
while *lock == 1 {
|
|
match cvar.wait(lock) {
|
|
Ok(l) => {
|
|
lock = l;
|
|
assert_eq!(*lock, 1);
|
|
}
|
|
Err(..) => break,
|
|
}
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_mutex_arc_poison() {
|
|
let arc = Arc::new(Mutex::new(1));
|
|
assert!(!arc.is_poisoned());
|
|
let arc2 = arc.clone();
|
|
let _ = thread::spawn(move|| {
|
|
let lock = arc2.lock().unwrap();
|
|
assert_eq!(*lock, 2);
|
|
}).join();
|
|
assert!(arc.lock().is_err());
|
|
assert!(arc.is_poisoned());
|
|
}
|
|
|
|
#[test]
|
|
fn test_mutex_arc_nested() {
|
|
// Tests nested mutexes and access
|
|
// to underlying data.
|
|
let arc = Arc::new(Mutex::new(1));
|
|
let arc2 = Arc::new(Mutex::new(arc));
|
|
let (tx, rx) = channel();
|
|
let _t = thread::spawn(move|| {
|
|
let lock = arc2.lock().unwrap();
|
|
let lock2 = lock.lock().unwrap();
|
|
assert_eq!(*lock2, 1);
|
|
tx.send(()).unwrap();
|
|
});
|
|
rx.recv().unwrap();
|
|
}
|
|
|
|
#[test]
|
|
fn test_mutex_arc_access_in_unwind() {
|
|
let arc = Arc::new(Mutex::new(1));
|
|
let arc2 = arc.clone();
|
|
let _ = thread::spawn(move|| -> () {
|
|
struct Unwinder {
|
|
i: Arc<Mutex<i32>>,
|
|
}
|
|
impl Drop for Unwinder {
|
|
fn drop(&mut self) {
|
|
*self.i.lock().unwrap() += 1;
|
|
}
|
|
}
|
|
let _u = Unwinder { i: arc2 };
|
|
panic!();
|
|
}).join();
|
|
let lock = arc.lock().unwrap();
|
|
assert_eq!(*lock, 2);
|
|
}
|
|
|
|
#[test]
|
|
fn test_mutex_unsized() {
|
|
let mutex: &Mutex<[i32]> = &Mutex::new([1, 2, 3]);
|
|
{
|
|
let b = &mut *mutex.lock().unwrap();
|
|
b[0] = 4;
|
|
b[2] = 5;
|
|
}
|
|
let comp: &[i32] = &[4, 2, 5];
|
|
assert_eq!(&*mutex.lock().unwrap(), comp);
|
|
}
|
|
}
|