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Diffstat (limited to 'src/libstd/sys_common/remutex.rs')
| -rw-r--r-- | src/libstd/sys_common/remutex.rs | 224 |
1 files changed, 0 insertions, 224 deletions
diff --git a/src/libstd/sys_common/remutex.rs b/src/libstd/sys_common/remutex.rs deleted file mode 100644 index 4f19bbc467f..00000000000 --- a/src/libstd/sys_common/remutex.rs +++ /dev/null @@ -1,224 +0,0 @@ -use crate::fmt; -use crate::marker; -use crate::ops::Deref; -use crate::panic::{RefUnwindSafe, UnwindSafe}; -use crate::sys::mutex as sys; - -/// A re-entrant mutual exclusion -/// -/// This mutex will block *other* threads waiting for the lock to become -/// available. The thread which has already locked the mutex can lock it -/// multiple times without blocking, preventing a common source of deadlocks. -pub struct ReentrantMutex<T> { - inner: sys::ReentrantMutex, - data: T, -} - -unsafe impl<T: Send> Send for ReentrantMutex<T> {} -unsafe impl<T: Send> Sync for ReentrantMutex<T> {} - -impl<T> UnwindSafe for ReentrantMutex<T> {} -impl<T> RefUnwindSafe for ReentrantMutex<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 implementation. -/// -/// # Mutability -/// -/// Unlike `MutexGuard`, `ReentrantMutexGuard` does not implement `DerefMut`, -/// because implementation of the trait would violate Rust’s reference aliasing -/// rules. Use interior mutability (usually `RefCell`) in order to mutate the -/// guarded data. -#[must_use = "if unused the ReentrantMutex will immediately unlock"] -pub struct ReentrantMutexGuard<'a, T: 'a> { - // funny underscores due to how Deref currently works (it disregards field - // privacy). - __lock: &'a ReentrantMutex<T>, -} - -impl<T> !marker::Send for ReentrantMutexGuard<'_, T> {} - -impl<T> ReentrantMutex<T> { - /// Creates a new reentrant mutex in an unlocked state. - /// - /// # Unsafety - /// - /// This function is unsafe because it is required that `init` is called - /// once this mutex is in its final resting place, and only then are the - /// lock/unlock methods safe. - pub const unsafe fn new(t: T) -> ReentrantMutex<T> { - ReentrantMutex { inner: sys::ReentrantMutex::uninitialized(), data: t } - } - - /// Initializes this mutex so it's ready for use. - /// - /// # Unsafety - /// - /// Unsafe to call more than once, and must be called after this will no - /// longer move in memory. - pub unsafe fn init(&self) { - self.inner.init(); - } - - /// Acquires a mutex, blocking the current thread until it is able to do so. - /// - /// This function will block the caller until it is available to acquire the mutex. - /// Upon returning, the thread is the only thread with the mutex held. When the thread - /// calling this method already holds the lock, the call shall succeed without - /// blocking. - /// - /// # 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. - pub fn lock(&self) -> ReentrantMutexGuard<'_, T> { - unsafe { self.inner.lock() } - ReentrantMutexGuard::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. - /// - /// 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. - pub fn try_lock(&self) -> Option<ReentrantMutexGuard<'_, T>> { - if unsafe { self.inner.try_lock() } { Some(ReentrantMutexGuard::new(&self)) } else { None } - } -} - -impl<T> Drop for ReentrantMutex<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) - unsafe { self.inner.destroy() } - } -} - -impl<T: fmt::Debug + 'static> fmt::Debug for ReentrantMutex<T> { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - match self.try_lock() { - Some(guard) => f.debug_struct("ReentrantMutex").field("data", &*guard).finish(), - None => { - struct LockedPlaceholder; - impl fmt::Debug for LockedPlaceholder { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.write_str("<locked>") - } - } - - f.debug_struct("ReentrantMutex").field("data", &LockedPlaceholder).finish() - } - } - } -} - -impl<'mutex, T> ReentrantMutexGuard<'mutex, T> { - fn new(lock: &'mutex ReentrantMutex<T>) -> ReentrantMutexGuard<'mutex, T> { - ReentrantMutexGuard { __lock: lock } - } -} - -impl<T> Deref for ReentrantMutexGuard<'_, T> { - type Target = T; - - fn deref(&self) -> &T { - &self.__lock.data - } -} - -impl<T> Drop for ReentrantMutexGuard<'_, T> { - #[inline] - fn drop(&mut self) { - unsafe { - self.__lock.inner.unlock(); - } - } -} - -#[cfg(all(test, not(target_os = "emscripten")))] -mod tests { - use crate::cell::RefCell; - use crate::sync::Arc; - use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard}; - use crate::thread; - - #[test] - fn smoke() { - let m = unsafe { - let m = ReentrantMutex::new(()); - m.init(); - m - }; - { - let a = m.lock(); - { - let b = m.lock(); - { - let c = m.lock(); - assert_eq!(*c, ()); - } - assert_eq!(*b, ()); - } - assert_eq!(*a, ()); - } - } - - #[test] - fn is_mutex() { - let m = unsafe { - let m = Arc::new(ReentrantMutex::new(RefCell::new(0))); - m.init(); - m - }; - 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 = unsafe { - let m = Arc::new(ReentrantMutex::new(())); - m.init(); - m - }; - 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(); - } - - pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>); - impl Drop for Answer<'_> { - fn drop(&mut self) { - *self.0.borrow_mut() = 42; - } - } -} |
