diff options
Diffstat (limited to 'library/std/src/sync/mutex.rs')
| -rw-r--r-- | library/std/src/sync/mutex.rs | 767 |
1 files changed, 767 insertions, 0 deletions
diff --git a/library/std/src/sync/mutex.rs b/library/std/src/sync/mutex.rs new file mode 100644 index 00000000000..8478457eabf --- /dev/null +++ b/library/std/src/sync/mutex.rs @@ -0,0 +1,767 @@ +use crate::cell::UnsafeCell; +use crate::fmt; +use crate::mem; +use crate::ops::{Deref, DerefMut}; +use crate::ptr; +use crate::sys_common::mutex as sys; +use crate::sys_common::poison::{self, LockResult, TryLockError, TryLockResult}; + +/// A mutual exclusion primitive useful for protecting shared data +/// +/// This mutex will block threads waiting for the lock to become available. The +/// mutex can also be statically initialized or created via a [`new`] +/// constructor. Each mutex has a type parameter which represents the data that +/// it is protecting. The data can only be accessed through the RAII guards +/// returned from [`lock`] and [`try_lock`], which guarantees that the data is only +/// ever accessed when the mutex is locked. +/// +/// # Poisoning +/// +/// The mutexes in this module implement a strategy called "poisoning" where a +/// mutex is considered poisoned whenever a thread panics while holding the +/// mutex. Once a mutex is poisoned, all other threads are unable to access the +/// data by default as it is likely tainted (some invariant is not being +/// upheld). +/// +/// For a mutex, this means that the [`lock`] and [`try_lock`] methods return a +/// [`Result`] which indicates whether a mutex has been poisoned or not. Most +/// usage of a mutex will simply [`unwrap()`] these results, propagating panics +/// among threads to ensure that a possibly invalid invariant is not witnessed. +/// +/// A poisoned mutex, however, does not prevent all access to the underlying +/// data. The [`PoisonError`] type has an [`into_inner`] method which will return +/// the guard that would have otherwise been returned on a successful lock. This +/// allows access to the data, despite the lock being poisoned. +/// +/// [`new`]: #method.new +/// [`lock`]: #method.lock +/// [`try_lock`]: #method.try_lock +/// [`Result`]: ../../std/result/enum.Result.html +/// [`unwrap()`]: ../../std/result/enum.Result.html#method.unwrap +/// [`PoisonError`]: ../../std/sync/struct.PoisonError.html +/// [`into_inner`]: ../../std/sync/struct.PoisonError.html#method.into_inner +/// +/// # Examples +/// +/// ``` +/// use std::sync::{Arc, Mutex}; +/// use std::thread; +/// use std::sync::mpsc::channel; +/// +/// const N: usize = 10; +/// +/// // Spawn a few threads to increment a shared variable (non-atomically), and +/// // let the main thread know once all increments are done. +/// // +/// // Here we're using an Arc to share memory among threads, and the data inside +/// // the Arc is protected with a mutex. +/// let data = Arc::new(Mutex::new(0)); +/// +/// let (tx, rx) = channel(); +/// for _ in 0..N { +/// let (data, tx) = (Arc::clone(&data), tx.clone()); +/// thread::spawn(move || { +/// // The shared state can only be accessed once the lock is held. +/// // Our non-atomic increment is safe because we're the only thread +/// // which can access the shared state when the lock is held. +/// // +/// // We unwrap() the return value to assert that we are not expecting +/// // threads to ever fail while holding the lock. +/// let mut data = data.lock().unwrap(); +/// *data += 1; +/// if *data == N { +/// tx.send(()).unwrap(); +/// } +/// // the lock is unlocked here when `data` goes out of scope. +/// }); +/// } +/// +/// rx.recv().unwrap(); +/// ``` +/// +/// To recover from a poisoned mutex: +/// +/// ``` +/// use std::sync::{Arc, Mutex}; +/// use std::thread; +/// +/// let lock = Arc::new(Mutex::new(0_u32)); +/// let lock2 = lock.clone(); +/// +/// let _ = thread::spawn(move || -> () { +/// // This thread will acquire the mutex first, unwrapping the result of +/// // `lock` because the lock has not been poisoned. +/// let _guard = lock2.lock().unwrap(); +/// +/// // This panic while holding the lock (`_guard` is in scope) will poison +/// // the mutex. +/// panic!(); +/// }).join(); +/// +/// // The lock is poisoned by this point, but the returned result can be +/// // pattern matched on to return the underlying guard on both branches. +/// let mut guard = match lock.lock() { +/// Ok(guard) => guard, +/// Err(poisoned) => poisoned.into_inner(), +/// }; +/// +/// *guard += 1; +/// ``` +/// +/// It is sometimes necessary to manually drop the mutex guard to unlock it +/// sooner than the end of the enclosing scope. +/// +/// ``` +/// use std::sync::{Arc, Mutex}; +/// use std::thread; +/// +/// const N: usize = 3; +/// +/// let data_mutex = Arc::new(Mutex::new(vec![1, 2, 3, 4])); +/// let res_mutex = Arc::new(Mutex::new(0)); +/// +/// let mut threads = Vec::with_capacity(N); +/// (0..N).for_each(|_| { +/// let data_mutex_clone = Arc::clone(&data_mutex); +/// let res_mutex_clone = Arc::clone(&res_mutex); +/// +/// threads.push(thread::spawn(move || { +/// let mut data = data_mutex_clone.lock().unwrap(); +/// // This is the result of some important and long-ish work. +/// let result = data.iter().fold(0, |acc, x| acc + x * 2); +/// data.push(result); +/// drop(data); +/// *res_mutex_clone.lock().unwrap() += result; +/// })); +/// }); +/// +/// let mut data = data_mutex.lock().unwrap(); +/// // This is the result of some important and long-ish work. +/// let result = data.iter().fold(0, |acc, x| acc + x * 2); +/// data.push(result); +/// // We drop the `data` explicitly because it's not necessary anymore and the +/// // thread still has work to do. This allow other threads to start working on +/// // the data immediately, without waiting for the rest of the unrelated work +/// // to be done here. +/// // +/// // It's even more important here than in the threads because we `.join` the +/// // threads after that. If we had not dropped the mutex guard, a thread could +/// // be waiting forever for it, causing a deadlock. +/// drop(data); +/// // Here the mutex guard is not assigned to a variable and so, even if the +/// // scope does not end after this line, the mutex is still released: there is +/// // no deadlock. +/// *res_mutex.lock().unwrap() += result; +/// +/// threads.into_iter().for_each(|thread| { +/// thread +/// .join() +/// .expect("The thread creating or execution failed !") +/// }); +/// +/// assert_eq!(*res_mutex.lock().unwrap(), 800); +/// ``` +#[stable(feature = "rust1", since = "1.0.0")] +#[cfg_attr(not(test), rustc_diagnostic_item = "mutex_type")] +pub struct Mutex<T: ?Sized> { + // Note that this mutex is in a *box*, not inlined into the struct itself. + // Once a native mutex has been used once, its address can never change (it + // can't be moved). This mutex type can be safely moved at any time, so to + // ensure that the native mutex is used correctly we box the inner mutex to + // give it a constant address. + inner: Box<sys::Mutex>, + poison: poison::Flag, + data: UnsafeCell<T>, +} + +// these are the only places where `T: Send` matters; all other +// functionality works fine on a single thread. +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<T: ?Sized + Send> Send for Mutex<T> {} +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<T: ?Sized + Send> Sync for Mutex<T> {} + +/// An RAII implementation of a "scoped lock" of a 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`] and [`DerefMut`] implementations. +/// +/// This structure is created by the [`lock`] and [`try_lock`] methods on +/// [`Mutex`]. +/// +/// [`Deref`]: ../../std/ops/trait.Deref.html +/// [`DerefMut`]: ../../std/ops/trait.DerefMut.html +/// [`lock`]: struct.Mutex.html#method.lock +/// [`try_lock`]: struct.Mutex.html#method.try_lock +/// [`Mutex`]: struct.Mutex.html +#[must_use = "if unused the Mutex will immediately unlock"] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct MutexGuard<'a, T: ?Sized + 'a> { + lock: &'a Mutex<T>, + poison: poison::Guard, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: ?Sized> !Send for MutexGuard<'_, T> {} +#[stable(feature = "mutexguard", since = "1.19.0")] +unsafe impl<T: ?Sized + Sync> Sync for MutexGuard<'_, T> {} + +impl<T> Mutex<T> { + /// Creates a new mutex in an unlocked state ready for use. + /// + /// # Examples + /// + /// ``` + /// use std::sync::Mutex; + /// + /// let mutex = Mutex::new(0); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn new(t: T) -> Mutex<T> { + let mut m = Mutex { + inner: box sys::Mutex::new(), + poison: poison::Flag::new(), + data: UnsafeCell::new(t), + }; + unsafe { + m.inner.init(); + } + m + } +} + +impl<T: ?Sized> Mutex<T> { + /// Acquires a mutex, blocking the current thread until it is able to do so. + /// + /// This function will block the local thread until it is available to acquire + /// the mutex. Upon returning, the thread is the only thread with the lock + /// held. An RAII guard is returned to allow scoped unlock of the lock. When + /// the guard goes out of scope, the mutex will be unlocked. + /// + /// The exact behavior on locking a mutex in the thread which already holds + /// the lock is left unspecified. However, this function will not return on + /// the second call (it might panic or deadlock, for example). + /// + /// # Errors + /// + /// If another user of this mutex panicked while holding the mutex, then + /// this call will return an error once the mutex is acquired. + /// + /// # Panics + /// + /// This function might panic when called if the lock is already held by + /// the current thread. + /// + /// # Examples + /// + /// ``` + /// use std::sync::{Arc, Mutex}; + /// use std::thread; + /// + /// let mutex = Arc::new(Mutex::new(0)); + /// let c_mutex = mutex.clone(); + /// + /// thread::spawn(move || { + /// *c_mutex.lock().unwrap() = 10; + /// }).join().expect("thread::spawn failed"); + /// assert_eq!(*mutex.lock().unwrap(), 10); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn lock(&self) -> LockResult<MutexGuard<'_, T>> { + unsafe { + self.inner.raw_lock(); + MutexGuard::new(self) + } + } + + /// Attempts to acquire this lock. + /// + /// If the lock could not be acquired at this time, then [`Err`] is returned. + /// Otherwise, an RAII guard is returned. The lock will be unlocked when the + /// guard is dropped. + /// + /// This function does not block. + /// + /// # Errors + /// + /// If another user of this mutex panicked while holding the mutex, then + /// this call will return failure if the mutex would otherwise be + /// acquired. + /// + /// [`Err`]: ../../std/result/enum.Result.html#variant.Err + /// + /// # Examples + /// + /// ``` + /// use std::sync::{Arc, Mutex}; + /// use std::thread; + /// + /// let mutex = Arc::new(Mutex::new(0)); + /// let c_mutex = mutex.clone(); + /// + /// thread::spawn(move || { + /// let mut lock = c_mutex.try_lock(); + /// if let Ok(ref mut mutex) = lock { + /// **mutex = 10; + /// } else { + /// println!("try_lock failed"); + /// } + /// }).join().expect("thread::spawn failed"); + /// assert_eq!(*mutex.lock().unwrap(), 10); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn try_lock(&self) -> TryLockResult<MutexGuard<'_, T>> { + unsafe { + if self.inner.try_lock() { + Ok(MutexGuard::new(self)?) + } else { + Err(TryLockError::WouldBlock) + } + } + } + + /// Determines whether the mutex is poisoned. + /// + /// If another thread is active, the mutex can still become poisoned at any + /// time. You should not trust a `false` value for program correctness + /// without additional synchronization. + /// + /// # Examples + /// + /// ``` + /// use std::sync::{Arc, Mutex}; + /// use std::thread; + /// + /// let mutex = Arc::new(Mutex::new(0)); + /// let c_mutex = mutex.clone(); + /// + /// let _ = thread::spawn(move || { + /// let _lock = c_mutex.lock().unwrap(); + /// panic!(); // the mutex gets poisoned + /// }).join(); + /// assert_eq!(mutex.is_poisoned(), true); + /// ``` + #[inline] + #[stable(feature = "sync_poison", since = "1.2.0")] + pub fn is_poisoned(&self) -> bool { + self.poison.get() + } + + /// Consumes this mutex, returning the underlying data. + /// + /// # Errors + /// + /// If another user of this mutex panicked while holding the mutex, then + /// this call will return an error instead. + /// + /// # Examples + /// + /// ``` + /// use std::sync::Mutex; + /// + /// let mutex = Mutex::new(0); + /// assert_eq!(mutex.into_inner().unwrap(), 0); + /// ``` + #[stable(feature = "mutex_into_inner", since = "1.6.0")] + pub fn into_inner(self) -> LockResult<T> + where + T: Sized, + { + // We know statically that there are no outstanding references to + // `self` so there's no need to lock the inner mutex. + // + // To get the inner value, we'd like to call `data.into_inner()`, + // but because `Mutex` impl-s `Drop`, we can't move out of it, so + // we'll have to destructure it manually instead. + unsafe { + // Like `let Mutex { inner, poison, data } = self`. + let (inner, poison, data) = { + let Mutex { ref inner, ref poison, ref data } = self; + (ptr::read(inner), ptr::read(poison), ptr::read(data)) + }; + mem::forget(self); + inner.destroy(); // Keep in sync with the `Drop` impl. + drop(inner); + + poison::map_result(poison.borrow(), |_| data.into_inner()) + } + } + + /// Returns a mutable reference to the underlying data. + /// + /// Since this call borrows the `Mutex` mutably, no actual locking needs to + /// take place -- the mutable borrow statically guarantees no locks exist. + /// + /// # Errors + /// + /// If another user of this mutex panicked while holding the mutex, then + /// this call will return an error instead. + /// + /// # Examples + /// + /// ``` + /// use std::sync::Mutex; + /// + /// let mut mutex = Mutex::new(0); + /// *mutex.get_mut().unwrap() = 10; + /// assert_eq!(*mutex.lock().unwrap(), 10); + /// ``` + #[stable(feature = "mutex_get_mut", since = "1.6.0")] + pub fn get_mut(&mut self) -> LockResult<&mut T> { + // We know statically that there are no other references to `self`, so + // there's no need to lock the inner mutex. + let data = unsafe { &mut *self.data.get() }; + poison::map_result(self.poison.borrow(), |_| data) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<#[may_dangle] T: ?Sized> Drop for Mutex<T> { + fn drop(&mut self) { + // This is actually safe b/c we know that there is no further usage of + // this mutex (it's up to the user to arrange for a mutex to get + // dropped, that's not our job) + // + // IMPORTANT: This code must be kept in sync with `Mutex::into_inner`. + unsafe { self.inner.destroy() } + } +} + +#[stable(feature = "mutex_from", since = "1.24.0")] +impl<T> From<T> for Mutex<T> { + /// Creates a new mutex in an unlocked state ready for use. + /// This is equivalent to [`Mutex::new`]. + /// + /// [`Mutex::new`]: ../../std/sync/struct.Mutex.html#method.new + fn from(t: T) -> Self { + Mutex::new(t) + } +} + +#[stable(feature = "mutex_default", since = "1.10.0")] +impl<T: ?Sized + Default> Default for Mutex<T> { + /// Creates a `Mutex<T>`, with the `Default` value for T. + fn default() -> Mutex<T> { + Mutex::new(Default::default()) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: ?Sized + fmt::Debug> fmt::Debug for Mutex<T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self.try_lock() { + Ok(guard) => f.debug_struct("Mutex").field("data", &&*guard).finish(), + Err(TryLockError::Poisoned(err)) => { + f.debug_struct("Mutex").field("data", &&**err.get_ref()).finish() + } + Err(TryLockError::WouldBlock) => { + struct LockedPlaceholder; + impl fmt::Debug for LockedPlaceholder { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.write_str("<locked>") + } + } + + f.debug_struct("Mutex").field("data", &LockedPlaceholder).finish() + } + } + } +} + +impl<'mutex, T: ?Sized> MutexGuard<'mutex, T> { + unsafe fn new(lock: &'mutex Mutex<T>) -> LockResult<MutexGuard<'mutex, T>> { + poison::map_result(lock.poison.borrow(), |guard| MutexGuard { lock, poison: guard }) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: ?Sized> Deref for MutexGuard<'_, T> { + type Target = T; + + fn deref(&self) -> &T { + unsafe { &*self.lock.data.get() } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: ?Sized> DerefMut for MutexGuard<'_, T> { + fn deref_mut(&mut self) -> &mut T { + unsafe { &mut *self.lock.data.get() } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: ?Sized> Drop for MutexGuard<'_, T> { + #[inline] + fn drop(&mut self) { + unsafe { + self.lock.poison.done(&self.poison); + self.lock.inner.raw_unlock(); + } + } +} + +#[stable(feature = "std_debug", since = "1.16.0")] +impl<T: ?Sized + fmt::Debug> fmt::Debug for MutexGuard<'_, T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Debug::fmt(&**self, f) + } +} + +#[stable(feature = "std_guard_impls", since = "1.20.0")] +impl<T: ?Sized + fmt::Display> fmt::Display for MutexGuard<'_, T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + (**self).fmt(f) + } +} + +pub fn guard_lock<'a, T: ?Sized>(guard: &MutexGuard<'a, T>) -> &'a sys::Mutex { + &guard.lock.inner +} + +pub fn guard_poison<'a, T: ?Sized>(guard: &MutexGuard<'a, T>) -> &'a poison::Flag { + &guard.lock.poison +} + +#[cfg(all(test, not(target_os = "emscripten")))] +mod tests { + use crate::sync::atomic::{AtomicUsize, Ordering}; + use crate::sync::mpsc::channel; + use crate::sync::{Arc, Condvar, Mutex}; + use crate::thread; + + struct Packet<T>(Arc<(Mutex<T>, Condvar)>); + + #[derive(Eq, PartialEq, Debug)] + struct NonCopy(i32); + + #[test] + fn smoke() { + let m = Mutex::new(()); + drop(m.lock().unwrap()); + drop(m.lock().unwrap()); + } + + #[test] + fn lots_and_lots() { + const J: u32 = 1000; + const K: u32 = 3; + + let m = Arc::new(Mutex::new(0)); + + fn inc(m: &Mutex<u32>) { + for _ in 0..J { + *m.lock().unwrap() += 1; + } + } + + let (tx, rx) = channel(); + for _ in 0..K { + 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); + } +} |