diff options
Diffstat (limited to 'library/std/src/sync')
| -rw-r--r-- | library/std/src/sync/lazy_lock.rs | 10 | ||||
| -rw-r--r-- | library/std/src/sync/lazy_lock/tests.rs | 6 | ||||
| -rw-r--r-- | library/std/src/sync/mod.rs | 3 | ||||
| -rw-r--r-- | library/std/src/sync/mutex/tests.rs | 2 | ||||
| -rw-r--r-- | library/std/src/sync/once_lock.rs | 17 | ||||
| -rw-r--r-- | library/std/src/sync/remutex.rs | 178 | ||||
| -rw-r--r-- | library/std/src/sync/remutex/tests.rs | 60 | ||||
| -rw-r--r-- | library/std/src/sync/rwlock/tests.rs | 4 |
8 files changed, 272 insertions, 8 deletions
diff --git a/library/std/src/sync/lazy_lock.rs b/library/std/src/sync/lazy_lock.rs index c8d3289ca..4a1530530 100644 --- a/library/std/src/sync/lazy_lock.rs +++ b/library/std/src/sync/lazy_lock.rs @@ -46,17 +46,15 @@ pub struct LazyLock<T, F = fn() -> T> { cell: OnceLock<T>, init: Cell<Option<F>>, } - -impl<T, F> LazyLock<T, F> { +impl<T, F: FnOnce() -> T> LazyLock<T, F> { /// Creates a new lazy value with the given initializing /// function. + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub const fn new(f: F) -> LazyLock<T, F> { LazyLock { cell: OnceLock::new(), init: Cell::new(Some(f)) } } -} -impl<T, F: FnOnce() -> T> LazyLock<T, F> { /// Forces the evaluation of this lazy value and /// returns a reference to result. This is equivalent /// to the `Deref` impl, but is explicit. @@ -73,6 +71,7 @@ impl<T, F: FnOnce() -> T> LazyLock<T, F> { /// assert_eq!(LazyLock::force(&lazy), &92); /// assert_eq!(&*lazy, &92); /// ``` + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn force(this: &LazyLock<T, F>) -> &T { this.cell.get_or_init(|| match this.init.take() { @@ -85,6 +84,8 @@ impl<T, F: FnOnce() -> T> LazyLock<T, F> { #[unstable(feature = "once_cell", issue = "74465")] impl<T, F: FnOnce() -> T> Deref for LazyLock<T, F> { type Target = T; + + #[inline] fn deref(&self) -> &T { LazyLock::force(self) } @@ -93,6 +94,7 @@ impl<T, F: FnOnce() -> T> Deref for LazyLock<T, F> { #[unstable(feature = "once_cell", issue = "74465")] impl<T: Default> Default for LazyLock<T> { /// Creates a new lazy value using `Default` as the initializing function. + #[inline] fn default() -> LazyLock<T> { LazyLock::new(T::default) } diff --git a/library/std/src/sync/lazy_lock/tests.rs b/library/std/src/sync/lazy_lock/tests.rs index f11b66bfc..a5d4e25c5 100644 --- a/library/std/src/sync/lazy_lock/tests.rs +++ b/library/std/src/sync/lazy_lock/tests.rs @@ -136,6 +136,12 @@ fn sync_lazy_poisoning() { } } +// Check that we can infer `T` from closure's type. +#[test] +fn lazy_type_inference() { + let _ = LazyCell::new(|| ()); +} + #[test] fn is_sync_send() { fn assert_traits<T: Send + Sync>() {} diff --git a/library/std/src/sync/mod.rs b/library/std/src/sync/mod.rs index 4fee8d3e9..ba20bab87 100644 --- a/library/std/src/sync/mod.rs +++ b/library/std/src/sync/mod.rs @@ -177,6 +177,8 @@ pub use self::lazy_lock::LazyLock; #[unstable(feature = "once_cell", issue = "74465")] pub use self::once_lock::OnceLock; +pub(crate) use self::remutex::{ReentrantMutex, ReentrantMutexGuard}; + pub mod mpsc; mod barrier; @@ -187,4 +189,5 @@ mod mutex; mod once; mod once_lock; mod poison; +mod remutex; mod rwlock; diff --git a/library/std/src/sync/mutex/tests.rs b/library/std/src/sync/mutex/tests.rs index 93900566f..1786a3c09 100644 --- a/library/std/src/sync/mutex/tests.rs +++ b/library/std/src/sync/mutex/tests.rs @@ -181,7 +181,7 @@ fn test_mutex_arc_poison() { let arc2 = arc.clone(); let _ = thread::spawn(move || { let lock = arc2.lock().unwrap(); - assert_eq!(*lock, 2); + assert_eq!(*lock, 2); // deliberate assertion failure to poison the mutex }) .join(); assert!(arc.lock().is_err()); diff --git a/library/std/src/sync/once_lock.rs b/library/std/src/sync/once_lock.rs index 16d1fd2a5..ed339ca5d 100644 --- a/library/std/src/sync/once_lock.rs +++ b/library/std/src/sync/once_lock.rs @@ -61,8 +61,9 @@ pub struct OnceLock<T> { impl<T> OnceLock<T> { /// Creates a new empty cell. - #[unstable(feature = "once_cell", issue = "74465")] + #[inline] #[must_use] + #[unstable(feature = "once_cell", issue = "74465")] pub const fn new() -> OnceLock<T> { OnceLock { once: Once::new(), @@ -75,6 +76,7 @@ impl<T> OnceLock<T> { /// /// Returns `None` if the cell is empty, or being initialized. This /// method never blocks. + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn get(&self) -> Option<&T> { if self.is_initialized() { @@ -88,6 +90,7 @@ impl<T> OnceLock<T> { /// Gets the mutable reference to the underlying value. /// /// Returns `None` if the cell is empty. This method never blocks. + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn get_mut(&mut self) -> Option<&mut T> { if self.is_initialized() { @@ -125,6 +128,7 @@ impl<T> OnceLock<T> { /// assert_eq!(CELL.get(), Some(&92)); /// } /// ``` + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn set(&self, value: T) -> Result<(), T> { let mut value = Some(value); @@ -164,6 +168,7 @@ impl<T> OnceLock<T> { /// let value = cell.get_or_init(|| unreachable!()); /// assert_eq!(value, &92); /// ``` + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn get_or_init<F>(&self, f: F) -> &T where @@ -203,6 +208,7 @@ impl<T> OnceLock<T> { /// assert_eq!(value, Ok(&92)); /// assert_eq!(cell.get(), Some(&92)) /// ``` + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn get_or_try_init<F, E>(&self, f: F) -> Result<&T, E> where @@ -241,6 +247,7 @@ impl<T> OnceLock<T> { /// cell.set("hello".to_string()).unwrap(); /// assert_eq!(cell.into_inner(), Some("hello".to_string())); /// ``` + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn into_inner(mut self) -> Option<T> { self.take() @@ -267,6 +274,7 @@ impl<T> OnceLock<T> { /// assert_eq!(cell.take(), Some("hello".to_string())); /// assert_eq!(cell.get(), None); /// ``` + #[inline] #[unstable(feature = "once_cell", issue = "74465")] pub fn take(&mut self) -> Option<T> { if self.is_initialized() { @@ -315,6 +323,7 @@ impl<T> OnceLock<T> { /// # Safety /// /// The value must be initialized + #[inline] unsafe fn get_unchecked(&self) -> &T { debug_assert!(self.is_initialized()); (&*self.value.get()).assume_init_ref() @@ -323,6 +332,7 @@ impl<T> OnceLock<T> { /// # Safety /// /// The value must be initialized + #[inline] unsafe fn get_unchecked_mut(&mut self) -> &mut T { debug_assert!(self.is_initialized()); (&mut *self.value.get()).assume_init_mut() @@ -360,6 +370,7 @@ impl<T> const Default for OnceLock<T> { /// assert_eq!(OnceLock::<()>::new(), OnceLock::default()); /// } /// ``` + #[inline] fn default() -> OnceLock<T> { OnceLock::new() } @@ -377,6 +388,7 @@ impl<T: fmt::Debug> fmt::Debug for OnceLock<T> { #[unstable(feature = "once_cell", issue = "74465")] impl<T: Clone> Clone for OnceLock<T> { + #[inline] fn clone(&self) -> OnceLock<T> { let cell = Self::new(); if let Some(value) = self.get() { @@ -408,6 +420,7 @@ impl<T> From<T> for OnceLock<T> { /// Ok(()) /// # } /// ``` + #[inline] fn from(value: T) -> Self { let cell = Self::new(); match cell.set(value) { @@ -419,6 +432,7 @@ impl<T> From<T> for OnceLock<T> { #[unstable(feature = "once_cell", issue = "74465")] impl<T: PartialEq> PartialEq for OnceLock<T> { + #[inline] fn eq(&self, other: &OnceLock<T>) -> bool { self.get() == other.get() } @@ -429,6 +443,7 @@ impl<T: Eq> Eq for OnceLock<T> {} #[unstable(feature = "once_cell", issue = "74465")] unsafe impl<#[may_dangle] T> Drop for OnceLock<T> { + #[inline] fn drop(&mut self) { if self.is_initialized() { // SAFETY: The cell is initialized and being dropped, so it can't diff --git a/library/std/src/sync/remutex.rs b/library/std/src/sync/remutex.rs new file mode 100644 index 000000000..4c054da64 --- /dev/null +++ b/library/std/src/sync/remutex.rs @@ -0,0 +1,178 @@ +#[cfg(all(test, not(target_os = "emscripten")))] +mod tests; + +use crate::cell::UnsafeCell; +use crate::ops::Deref; +use crate::panic::{RefUnwindSafe, UnwindSafe}; +use crate::sync::atomic::{AtomicUsize, Ordering::Relaxed}; +use crate::sys::locks 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. +/// +/// This is used by stdout().lock() and friends. +/// +/// ## Implementation details +/// +/// The 'owner' field tracks which thread has locked the mutex. +/// +/// We use current_thread_unique_ptr() as the thread identifier, +/// which is just the address of a thread local variable. +/// +/// If `owner` is set to the identifier of the current thread, +/// we assume the mutex is already locked and instead of locking it again, +/// we increment `lock_count`. +/// +/// When unlocking, we decrement `lock_count`, and only unlock the mutex when +/// it reaches zero. +/// +/// `lock_count` is protected by the mutex and only accessed by the thread that has +/// locked the mutex, so needs no synchronization. +/// +/// `owner` can be checked by other threads that want to see if they already +/// hold the lock, so needs to be atomic. If it compares equal, we're on the +/// same thread that holds the mutex and memory access can use relaxed ordering +/// since we're not dealing with multiple threads. If it compares unequal, +/// synchronization is left to the mutex, making relaxed memory ordering for +/// the `owner` field fine in all cases. +pub struct ReentrantMutex<T> { + mutex: sys::Mutex, + owner: AtomicUsize, + lock_count: UnsafeCell<u32>, + 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> { + lock: &'a ReentrantMutex<T>, +} + +impl<T> !Send for ReentrantMutexGuard<'_, T> {} + +impl<T> ReentrantMutex<T> { + /// Creates a new reentrant mutex in an unlocked state. + pub const fn new(t: T) -> ReentrantMutex<T> { + ReentrantMutex { + mutex: sys::Mutex::new(), + owner: AtomicUsize::new(0), + lock_count: UnsafeCell::new(0), + data: t, + } + } + + /// 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> { + let this_thread = current_thread_unique_ptr(); + // Safety: We only touch lock_count when we own the lock. + unsafe { + if self.owner.load(Relaxed) == this_thread { + self.increment_lock_count(); + } else { + self.mutex.lock(); + self.owner.store(this_thread, Relaxed); + debug_assert_eq!(*self.lock_count.get(), 0); + *self.lock_count.get() = 1; + } + } + ReentrantMutexGuard { lock: 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>> { + let this_thread = current_thread_unique_ptr(); + // Safety: We only touch lock_count when we own the lock. + unsafe { + if self.owner.load(Relaxed) == this_thread { + self.increment_lock_count(); + Some(ReentrantMutexGuard { lock: self }) + } else if self.mutex.try_lock() { + self.owner.store(this_thread, Relaxed); + debug_assert_eq!(*self.lock_count.get(), 0); + *self.lock_count.get() = 1; + Some(ReentrantMutexGuard { lock: self }) + } else { + None + } + } + } + + unsafe fn increment_lock_count(&self) { + *self.lock_count.get() = (*self.lock_count.get()) + .checked_add(1) + .expect("lock count overflow in reentrant mutex"); + } +} + +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) { + // Safety: We own the lock. + unsafe { + *self.lock.lock_count.get() -= 1; + if *self.lock.lock_count.get() == 0 { + self.lock.owner.store(0, Relaxed); + self.lock.mutex.unlock(); + } + } + } +} + +/// Get an address that is unique per running thread. +/// +/// This can be used as a non-null usize-sized ID. +pub fn current_thread_unique_ptr() -> usize { + // Use a non-drop type to make sure it's still available during thread destruction. + thread_local! { static X: u8 = const { 0 } } + X.with(|x| <*const _>::addr(x)) +} diff --git a/library/std/src/sync/remutex/tests.rs b/library/std/src/sync/remutex/tests.rs new file mode 100644 index 000000000..fc553081d --- /dev/null +++ b/library/std/src/sync/remutex/tests.rs @@ -0,0 +1,60 @@ +use super::{ReentrantMutex, ReentrantMutexGuard}; +use crate::cell::RefCell; +use crate::sync::Arc; +use crate::thread; + +#[test] +fn smoke() { + let m = ReentrantMutex::new(()); + { + 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 = 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(); +} + +pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>); +impl Drop for Answer<'_> { + fn drop(&mut self) { + *self.0.borrow_mut() = 42; + } +} diff --git a/library/std/src/sync/rwlock/tests.rs b/library/std/src/sync/rwlock/tests.rs index b5b3ad989..1a9d3d3f1 100644 --- a/library/std/src/sync/rwlock/tests.rs +++ b/library/std/src/sync/rwlock/tests.rs @@ -2,7 +2,7 @@ use crate::sync::atomic::{AtomicUsize, Ordering}; use crate::sync::mpsc::channel; use crate::sync::{Arc, RwLock, RwLockReadGuard, TryLockError}; use crate::thread; -use rand::{self, Rng}; +use rand::Rng; #[derive(Eq, PartialEq, Debug)] struct NonCopy(i32); @@ -28,7 +28,7 @@ fn frob() { let tx = tx.clone(); let r = r.clone(); thread::spawn(move || { - let mut rng = rand::thread_rng(); + let mut rng = crate::test_helpers::test_rng(); for _ in 0..M { if rng.gen_bool(1.0 / (N as f64)) { drop(r.write().unwrap()); |