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-// Copyright 2018 Amanieu d'Antras
-//
-// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
-// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
-// http://opensource.org/licenses/MIT>, at your option. This file may not be
-// copied, modified, or distributed except according to those terms.
-
-use core::cell::UnsafeCell;
-use core::fmt;
-use core::marker::PhantomData;
-use core::mem;
-use core::ops::{Deref, DerefMut};
-
-#[cfg(feature = "arc_lock")]
-use alloc::sync::Arc;
-#[cfg(feature = "arc_lock")]
-use core::mem::ManuallyDrop;
-#[cfg(feature = "arc_lock")]
-use core::ptr;
-
-#[cfg(feature = "owning_ref")]
-use owning_ref::StableAddress;
-
-#[cfg(feature = "serde")]
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
-
-/// Basic operations for a mutex.
-///
-/// Types implementing this trait can be used by `Mutex` to form a safe and
-/// fully-functioning mutex type.
-///
-/// # Safety
-///
-/// Implementations of this trait must ensure that the mutex is actually
-/// exclusive: a lock can't be acquired while the mutex is already locked.
-pub unsafe trait RawMutex {
- /// Initial value for an unlocked mutex.
- // A “non-constant” const item is a legacy way to supply an initialized value to downstream
- // static items. Can hopefully be replaced with `const fn new() -> Self` at some point.
- #[allow(clippy::declare_interior_mutable_const)]
- const INIT: Self;
-
- /// Marker type which determines whether a lock guard should be `Send`. Use
- /// one of the `GuardSend` or `GuardNoSend` helper types here.
- type GuardMarker;
-
- /// Acquires this mutex, blocking the current thread until it is able to do so.
- fn lock(&self);
-
- /// Attempts to acquire this mutex without blocking. Returns `true`
- /// if the lock was successfully acquired and `false` otherwise.
- fn try_lock(&self) -> bool;
-
- /// Unlocks this mutex.
- ///
- /// # Safety
- ///
- /// This method may only be called if the mutex is held in the current context, i.e. it must
- /// be paired with a successful call to [`lock`], [`try_lock`], [`try_lock_for`] or [`try_lock_until`].
- ///
- /// [`lock`]: #tymethod.lock
- /// [`try_lock`]: #tymethod.try_lock
- /// [`try_lock_for`]: trait.RawMutexTimed.html#tymethod.try_lock_for
- /// [`try_lock_until`]: trait.RawMutexTimed.html#tymethod.try_lock_until
- unsafe fn unlock(&self);
-
- /// Checks whether the mutex is currently locked.
- #[inline]
- fn is_locked(&self) -> bool {
- let acquired_lock = self.try_lock();
- if acquired_lock {
- // Safety: The lock has been successfully acquired above.
- unsafe {
- self.unlock();
- }
- }
- !acquired_lock
- }
-}
-
-/// Additional methods for mutexes which support fair unlocking.
-///
-/// Fair unlocking means that a lock is handed directly over to the next waiting
-/// thread if there is one, without giving other threads the opportunity to
-/// "steal" the lock in the meantime. This is typically slower than unfair
-/// unlocking, but may be necessary in certain circumstances.
-pub unsafe trait RawMutexFair: RawMutex {
- /// Unlocks this mutex using a fair unlock protocol.
- ///
- /// # Safety
- ///
- /// This method may only be called if the mutex is held in the current context, see
- /// the documentation of [`unlock`].
- ///
- /// [`unlock`]: trait.RawMutex.html#tymethod.unlock
- unsafe fn unlock_fair(&self);
-
- /// Temporarily yields the mutex to a waiting thread if there is one.
- ///
- /// This method is functionally equivalent to calling `unlock_fair` followed
- /// by `lock`, however it can be much more efficient in the case where there
- /// are no waiting threads.
- ///
- /// # Safety
- ///
- /// This method may only be called if the mutex is held in the current context, see
- /// the documentation of [`unlock`].
- ///
- /// [`unlock`]: trait.RawMutex.html#tymethod.unlock
- unsafe fn bump(&self) {
- self.unlock_fair();
- self.lock();
- }
-}
-
-/// Additional methods for mutexes which support locking with timeouts.
-///
-/// The `Duration` and `Instant` types are specified as associated types so that
-/// this trait is usable even in `no_std` environments.
-pub unsafe trait RawMutexTimed: RawMutex {
- /// Duration type used for `try_lock_for`.
- type Duration;
-
- /// Instant type used for `try_lock_until`.
- type Instant;
-
- /// Attempts to acquire this lock until a timeout is reached.
- fn try_lock_for(&self, timeout: Self::Duration) -> bool;
-
- /// Attempts to acquire this lock until a timeout is reached.
- fn try_lock_until(&self, timeout: Self::Instant) -> bool;
-}
-
-/// 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.
-pub struct Mutex<R, T: ?Sized> {
- raw: R,
- data: UnsafeCell<T>,
-}
-
-unsafe impl<R: RawMutex + Send, T: ?Sized + Send> Send for Mutex<R, T> {}
-unsafe impl<R: RawMutex + Sync, T: ?Sized + Send> Sync for Mutex<R, T> {}
-
-impl<R: RawMutex, T> Mutex<R, T> {
- /// Creates a new mutex in an unlocked state ready for use.
- #[cfg(has_const_fn_trait_bound)]
- #[inline]
- pub const fn new(val: T) -> Mutex<R, T> {
- Mutex {
- raw: R::INIT,
- data: UnsafeCell::new(val),
- }
- }
-
- /// Creates a new mutex in an unlocked state ready for use.
- #[cfg(not(has_const_fn_trait_bound))]
- #[inline]
- pub fn new(val: T) -> Mutex<R, T> {
- Mutex {
- raw: R::INIT,
- data: UnsafeCell::new(val),
- }
- }
-
- /// Consumes this mutex, returning the underlying data.
- #[inline]
- pub fn into_inner(self) -> T {
- self.data.into_inner()
- }
-}
-
-impl<R, T> Mutex<R, T> {
- /// Creates a new mutex based on a pre-existing raw mutex.
- ///
- /// This allows creating a mutex in a constant context on stable Rust.
- #[inline]
- pub const fn const_new(raw_mutex: R, val: T) -> Mutex<R, T> {
- Mutex {
- raw: raw_mutex,
- data: UnsafeCell::new(val),
- }
- }
-}
-
-impl<R: RawMutex, T: ?Sized> Mutex<R, T> {
- /// Creates a new `MutexGuard` without checking if the mutex is locked.
- ///
- /// # Safety
- ///
- /// This method must only be called if the thread logically holds the lock.
- ///
- /// Calling this function when a guard has already been produced is undefined behaviour unless
- /// the guard was forgotten with `mem::forget`.
- #[inline]
- pub unsafe fn make_guard_unchecked(&self) -> MutexGuard<'_, R, T> {
- MutexGuard {
- mutex: self,
- marker: PhantomData,
- }
- }
-
- /// 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 mutex
- /// 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.
- ///
- /// Attempts to lock a mutex in the thread which already holds the lock will
- /// result in a deadlock.
- #[inline]
- pub fn lock(&self) -> MutexGuard<'_, R, T> {
- self.raw.lock();
- // SAFETY: The lock is held, as required.
- unsafe { self.make_guard_unchecked() }
- }
-
- /// Attempts to acquire this lock.
- ///
- /// If the lock could not be acquired at this time, then `None` is returned.
- /// Otherwise, an RAII guard is returned. The lock will be unlocked when the
- /// guard is dropped.
- ///
- /// This function does not block.
- #[inline]
- pub fn try_lock(&self) -> Option<MutexGuard<'_, R, T>> {
- if self.raw.try_lock() {
- // SAFETY: The lock is held, as required.
- Some(unsafe { self.make_guard_unchecked() })
- } else {
- None
- }
- }
-
- /// 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.
- #[inline]
- pub fn get_mut(&mut self) -> &mut T {
- unsafe { &mut *self.data.get() }
- }
-
- /// Checks whether the mutex is currently locked.
- #[inline]
- pub fn is_locked(&self) -> bool {
- self.raw.is_locked()
- }
-
- /// Forcibly unlocks the mutex.
- ///
- /// This is useful when combined with `mem::forget` to hold a lock without
- /// the need to maintain a `MutexGuard` object alive, for example when
- /// dealing with FFI.
- ///
- /// # Safety
- ///
- /// This method must only be called if the current thread logically owns a
- /// `MutexGuard` but that guard has been discarded using `mem::forget`.
- /// Behavior is undefined if a mutex is unlocked when not locked.
- #[inline]
- pub unsafe fn force_unlock(&self) {
- self.raw.unlock();
- }
-
- /// Returns the underlying raw mutex object.
- ///
- /// Note that you will most likely need to import the `RawMutex` trait from
- /// `lock_api` to be able to call functions on the raw mutex.
- ///
- /// # Safety
- ///
- /// This method is unsafe because it allows unlocking a mutex while
- /// still holding a reference to a `MutexGuard`.
- #[inline]
- pub unsafe fn raw(&self) -> &R {
- &self.raw
- }
-
- /// Returns a raw pointer to the underlying data.
- ///
- /// This is useful when combined with `mem::forget` to hold a lock without
- /// the need to maintain a `MutexGuard` object alive, for example when
- /// dealing with FFI.
- ///
- /// # Safety
- ///
- /// You must ensure that there are no data races when dereferencing the
- /// returned pointer, for example if the current thread logically owns
- /// a `MutexGuard` but that guard has been discarded using `mem::forget`.
- #[inline]
- pub fn data_ptr(&self) -> *mut T {
- self.data.get()
- }
-
- /// Creates a new `ArcMutexGuard` without checking if the mutex is locked.
- ///
- /// # Safety
- ///
- /// This method must only be called if the thread logically holds the lock.
- ///
- /// Calling this function when a guard has already been produced is undefined behaviour unless
- /// the guard was forgotten with `mem::forget`.
- #[cfg(feature = "arc_lock")]
- #[inline]
- unsafe fn make_arc_guard_unchecked(self: &Arc<Self>) -> ArcMutexGuard<R, T> {
- ArcMutexGuard {
- mutex: self.clone(),
- marker: PhantomData,
- }
- }
-
- /// Acquires a lock through an `Arc`.
- ///
- /// This method is similar to the `lock` method; however, it requires the `Mutex` to be inside of an `Arc`
- /// and the resulting mutex guard has no lifetime requirements.
- #[cfg(feature = "arc_lock")]
- #[inline]
- pub fn lock_arc(self: &Arc<Self>) -> ArcMutexGuard<R, T> {
- self.raw.lock();
- // SAFETY: the locking guarantee is upheld
- unsafe { self.make_arc_guard_unchecked() }
- }
-
- /// Attempts to acquire a lock through an `Arc`.
- ///
- /// This method is similar to the `try_lock` method; however, it requires the `Mutex` to be inside of an
- /// `Arc` and the resulting mutex guard has no lifetime requirements.
- #[cfg(feature = "arc_lock")]
- #[inline]
- pub fn try_lock_arc(self: &Arc<Self>) -> Option<ArcMutexGuard<R, T>> {
- if self.raw.try_lock() {
- // SAFETY: locking guarantee is upheld
- Some(unsafe { self.make_arc_guard_unchecked() })
- } else {
- None
- }
- }
-}
-
-impl<R: RawMutexFair, T: ?Sized> Mutex<R, T> {
- /// Forcibly unlocks the mutex using a fair unlock procotol.
- ///
- /// This is useful when combined with `mem::forget` to hold a lock without
- /// the need to maintain a `MutexGuard` object alive, for example when
- /// dealing with FFI.
- ///
- /// # Safety
- ///
- /// This method must only be called if the current thread logically owns a
- /// `MutexGuard` but that guard has been discarded using `mem::forget`.
- /// Behavior is undefined if a mutex is unlocked when not locked.
- #[inline]
- pub unsafe fn force_unlock_fair(&self) {
- self.raw.unlock_fair();
- }
-}
-
-impl<R: RawMutexTimed, T: ?Sized> Mutex<R, T> {
- /// Attempts to acquire this lock until a timeout is reached.
- ///
- /// If the lock could not be acquired before the timeout expired, then
- /// `None` is returned. Otherwise, an RAII guard is returned. The lock will
- /// be unlocked when the guard is dropped.
- #[inline]
- pub fn try_lock_for(&self, timeout: R::Duration) -> Option<MutexGuard<'_, R, T>> {
- if self.raw.try_lock_for(timeout) {
- // SAFETY: The lock is held, as required.
- Some(unsafe { self.make_guard_unchecked() })
- } else {
- None
- }
- }
-
- /// Attempts to acquire this lock until a timeout is reached.
- ///
- /// If the lock could not be acquired before the timeout expired, then
- /// `None` is returned. Otherwise, an RAII guard is returned. The lock will
- /// be unlocked when the guard is dropped.
- #[inline]
- pub fn try_lock_until(&self, timeout: R::Instant) -> Option<MutexGuard<'_, R, T>> {
- if self.raw.try_lock_until(timeout) {
- // SAFETY: The lock is held, as required.
- Some(unsafe { self.make_guard_unchecked() })
- } else {
- None
- }
- }
-
- /// Attempts to acquire this lock through an `Arc` until a timeout is reached.
- ///
- /// This method is similar to the `try_lock_for` method; however, it requires the `Mutex` to be inside of an
- /// `Arc` and the resulting mutex guard has no lifetime requirements.
- #[cfg(feature = "arc_lock")]
- #[inline]
- pub fn try_lock_arc_for(self: &Arc<Self>, timeout: R::Duration) -> Option<ArcMutexGuard<R, T>> {
- if self.raw.try_lock_for(timeout) {
- // SAFETY: locking guarantee is upheld
- Some(unsafe { self.make_arc_guard_unchecked() })
- } else {
- None
- }
- }
-
- /// Attempts to acquire this lock through an `Arc` until a timeout is reached.
- ///
- /// This method is similar to the `try_lock_until` method; however, it requires the `Mutex` to be inside of
- /// an `Arc` and the resulting mutex guard has no lifetime requirements.
- #[cfg(feature = "arc_lock")]
- #[inline]
- pub fn try_lock_arc_until(
- self: &Arc<Self>,
- timeout: R::Instant,
- ) -> Option<ArcMutexGuard<R, T>> {
- if self.raw.try_lock_until(timeout) {
- // SAFETY: locking guarantee is upheld
- Some(unsafe { self.make_arc_guard_unchecked() })
- } else {
- None
- }
- }
-}
-
-impl<R: RawMutex, T: ?Sized + Default> Default for Mutex<R, T> {
- #[inline]
- fn default() -> Mutex<R, T> {
- Mutex::new(Default::default())
- }
-}
-
-impl<R: RawMutex, T> From<T> for Mutex<R, T> {
- #[inline]
- fn from(t: T) -> Mutex<R, T> {
- Mutex::new(t)
- }
-}
-
-impl<R: RawMutex, T: ?Sized + fmt::Debug> fmt::Debug for Mutex<R, T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- match self.try_lock() {
- Some(guard) => f.debug_struct("Mutex").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("Mutex")
- .field("data", &LockedPlaceholder)
- .finish()
- }
- }
- }
-}
-
-// Copied and modified from serde
-#[cfg(feature = "serde")]
-impl<R, T> Serialize for Mutex<R, T>
-where
- R: RawMutex,
- T: Serialize + ?Sized,
-{
- fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
- where
- S: Serializer,
- {
- self.lock().serialize(serializer)
- }
-}
-
-#[cfg(feature = "serde")]
-impl<'de, R, T> Deserialize<'de> for Mutex<R, T>
-where
- R: RawMutex,
- T: Deserialize<'de> + ?Sized,
-{
- fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
- where
- D: Deserializer<'de>,
- {
- Deserialize::deserialize(deserializer).map(Mutex::new)
- }
-}
-
-/// 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.
-#[clippy::has_significant_drop]
-#[must_use = "if unused the Mutex will immediately unlock"]
-pub struct MutexGuard<'a, R: RawMutex, T: ?Sized> {
- mutex: &'a Mutex<R, T>,
- marker: PhantomData<(&'a mut T, R::GuardMarker)>,
-}
-
-unsafe impl<'a, R: RawMutex + Sync + 'a, T: ?Sized + Sync + 'a> Sync for MutexGuard<'a, R, T> {}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> MutexGuard<'a, R, T> {
- /// Returns a reference to the original `Mutex` object.
- pub fn mutex(s: &Self) -> &'a Mutex<R, T> {
- s.mutex
- }
-
- /// Makes a new `MappedMutexGuard` for a component of the locked data.
- ///
- /// This operation cannot fail as the `MutexGuard` passed
- /// in already locked the mutex.
- ///
- /// This is an associated function that needs to be
- /// used as `MutexGuard::map(...)`. A method would interfere with methods of
- /// the same name on the contents of the locked data.
- #[inline]
- pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedMutexGuard<'a, R, U>
- where
- F: FnOnce(&mut T) -> &mut U,
- {
- let raw = &s.mutex.raw;
- let data = f(unsafe { &mut *s.mutex.data.get() });
- mem::forget(s);
- MappedMutexGuard {
- raw,
- data,
- marker: PhantomData,
- }
- }
-
- /// Attempts to make a new `MappedMutexGuard` for a component of the
- /// locked data. The original guard is returned if the closure returns `None`.
- ///
- /// This operation cannot fail as the `MutexGuard` passed
- /// in already locked the mutex.
- ///
- /// This is an associated function that needs to be
- /// used as `MutexGuard::try_map(...)`. A method would interfere with methods of
- /// the same name on the contents of the locked data.
- #[inline]
- pub fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedMutexGuard<'a, R, U>, Self>
- where
- F: FnOnce(&mut T) -> Option<&mut U>,
- {
- let raw = &s.mutex.raw;
- let data = match f(unsafe { &mut *s.mutex.data.get() }) {
- Some(data) => data,
- None => return Err(s),
- };
- mem::forget(s);
- Ok(MappedMutexGuard {
- raw,
- data,
- marker: PhantomData,
- })
- }
-
- /// Temporarily unlocks the mutex to execute the given function.
- ///
- /// This is safe because `&mut` guarantees that there exist no other
- /// references to the data protected by the mutex.
- #[inline]
- pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
- where
- F: FnOnce() -> U,
- {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.unlock();
- }
- defer!(s.mutex.raw.lock());
- f()
- }
-
- /// Leaks the mutex guard and returns a mutable reference to the data
- /// protected by the mutex.
- ///
- /// This will leave the `Mutex` in a locked state.
- #[inline]
- pub fn leak(s: Self) -> &'a mut T {
- let r = unsafe { &mut *s.mutex.data.get() };
- mem::forget(s);
- r
- }
-}
-
-impl<'a, R: RawMutexFair + 'a, T: ?Sized + 'a> MutexGuard<'a, R, T> {
- /// Unlocks the mutex using a fair unlock protocol.
- ///
- /// By default, mutexes are unfair and allow the current thread to re-lock
- /// the mutex before another has the chance to acquire the lock, even if
- /// that thread has been blocked on the mutex for a long time. This is the
- /// default because it allows much higher throughput as it avoids forcing a
- /// context switch on every mutex unlock. This can result in one thread
- /// acquiring a mutex many more times than other threads.
- ///
- /// However in some cases it can be beneficial to ensure fairness by forcing
- /// the lock to pass on to a waiting thread if there is one. This is done by
- /// using this method instead of dropping the `MutexGuard` normally.
- #[inline]
- pub fn unlock_fair(s: Self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.unlock_fair();
- }
- mem::forget(s);
- }
-
- /// Temporarily unlocks the mutex to execute the given function.
- ///
- /// The mutex is unlocked using a fair unlock protocol.
- ///
- /// This is safe because `&mut` guarantees that there exist no other
- /// references to the data protected by the mutex.
- #[inline]
- pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
- where
- F: FnOnce() -> U,
- {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.unlock_fair();
- }
- defer!(s.mutex.raw.lock());
- f()
- }
-
- /// Temporarily yields the mutex to a waiting thread if there is one.
- ///
- /// This method is functionally equivalent to calling `unlock_fair` followed
- /// by `lock`, however it can be much more efficient in the case where there
- /// are no waiting threads.
- #[inline]
- pub fn bump(s: &mut Self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.bump();
- }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Deref for MutexGuard<'a, R, T> {
- type Target = T;
- #[inline]
- fn deref(&self) -> &T {
- unsafe { &*self.mutex.data.get() }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MutexGuard<'a, R, T> {
- #[inline]
- fn deref_mut(&mut self) -> &mut T {
- unsafe { &mut *self.mutex.data.get() }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Drop for MutexGuard<'a, R, T> {
- #[inline]
- fn drop(&mut self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- self.mutex.raw.unlock();
- }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug for MutexGuard<'a, R, T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Debug::fmt(&**self, f)
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display for MutexGuard<'a, R, T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- (**self).fmt(f)
- }
-}
-
-#[cfg(feature = "owning_ref")]
-unsafe impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> StableAddress for MutexGuard<'a, R, T> {}
-
-/// An RAII mutex guard returned by the `Arc` locking operations on `Mutex`.
-///
-/// This is similar to the `MutexGuard` struct, except instead of using a reference to unlock the `Mutex` it
-/// uses an `Arc<Mutex>`. This has several advantages, most notably that it has an `'static` lifetime.
-#[cfg(feature = "arc_lock")]
-#[clippy::has_significant_drop]
-#[must_use = "if unused the Mutex will immediately unlock"]
-pub struct ArcMutexGuard<R: RawMutex, T: ?Sized> {
- mutex: Arc<Mutex<R, T>>,
- marker: PhantomData<*const ()>,
-}
-
-#[cfg(feature = "arc_lock")]
-unsafe impl<R: RawMutex + Send + Sync, T: Send + ?Sized> Send for ArcMutexGuard<R, T> where
- R::GuardMarker: Send
-{
-}
-#[cfg(feature = "arc_lock")]
-unsafe impl<R: RawMutex + Sync, T: Sync + ?Sized> Sync for ArcMutexGuard<R, T> where
- R::GuardMarker: Sync
-{
-}
-
-#[cfg(feature = "arc_lock")]
-impl<R: RawMutex, T: ?Sized> ArcMutexGuard<R, T> {
- /// Returns a reference to the `Mutex` this is guarding, contained in its `Arc`.
- #[inline]
- pub fn mutex(s: &Self) -> &Arc<Mutex<R, T>> {
- &s.mutex
- }
-
- /// Unlocks the mutex and returns the `Arc` that was held by the [`ArcMutexGuard`].
- #[inline]
- pub fn into_arc(s: Self) -> Arc<Mutex<R, T>> {
- // Safety: Skip our Drop impl and manually unlock the mutex.
- let arc = unsafe { ptr::read(&s.mutex) };
- mem::forget(s);
- unsafe {
- arc.raw.unlock();
- }
- arc
- }
-
- /// Temporarily unlocks the mutex to execute the given function.
- ///
- /// This is safe because `&mut` guarantees that there exist no other
- /// references to the data protected by the mutex.
- #[inline]
- pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
- where
- F: FnOnce() -> U,
- {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.unlock();
- }
- defer!(s.mutex.raw.lock());
- f()
- }
-}
-
-#[cfg(feature = "arc_lock")]
-impl<R: RawMutexFair, T: ?Sized> ArcMutexGuard<R, T> {
- /// Unlocks the mutex using a fair unlock protocol.
- ///
- /// This is functionally identical to the `unlock_fair` method on [`MutexGuard`].
- #[inline]
- pub fn unlock_fair(s: Self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.unlock_fair();
- }
-
- // SAFETY: make sure the Arc gets it reference decremented
- let mut s = ManuallyDrop::new(s);
- unsafe { ptr::drop_in_place(&mut s.mutex) };
- }
-
- /// Temporarily unlocks the mutex to execute the given function.
- ///
- /// This is functionally identical to the `unlocked_fair` method on [`MutexGuard`].
- #[inline]
- pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
- where
- F: FnOnce() -> U,
- {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.unlock_fair();
- }
- defer!(s.mutex.raw.lock());
- f()
- }
-
- /// Temporarily yields the mutex to a waiting thread if there is one.
- ///
- /// This is functionally identical to the `bump` method on [`MutexGuard`].
- #[inline]
- pub fn bump(s: &mut Self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.mutex.raw.bump();
- }
- }
-}
-
-#[cfg(feature = "arc_lock")]
-impl<R: RawMutex, T: ?Sized> Deref for ArcMutexGuard<R, T> {
- type Target = T;
- #[inline]
- fn deref(&self) -> &T {
- unsafe { &*self.mutex.data.get() }
- }
-}
-
-#[cfg(feature = "arc_lock")]
-impl<R: RawMutex, T: ?Sized> DerefMut for ArcMutexGuard<R, T> {
- #[inline]
- fn deref_mut(&mut self) -> &mut T {
- unsafe { &mut *self.mutex.data.get() }
- }
-}
-
-#[cfg(feature = "arc_lock")]
-impl<R: RawMutex, T: ?Sized> Drop for ArcMutexGuard<R, T> {
- #[inline]
- fn drop(&mut self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- self.mutex.raw.unlock();
- }
- }
-}
-
-/// An RAII mutex guard returned by `MutexGuard::map`, which can point to a
-/// subfield of the protected data.
-///
-/// The main difference between `MappedMutexGuard` and `MutexGuard` is that the
-/// former doesn't support temporarily unlocking and re-locking, since that
-/// could introduce soundness issues if the locked object is modified by another
-/// thread.
-#[clippy::has_significant_drop]
-#[must_use = "if unused the Mutex will immediately unlock"]
-pub struct MappedMutexGuard<'a, R: RawMutex, T: ?Sized> {
- raw: &'a R,
- data: *mut T,
- marker: PhantomData<&'a mut T>,
-}
-
-unsafe impl<'a, R: RawMutex + Sync + 'a, T: ?Sized + Sync + 'a> Sync
- for MappedMutexGuard<'a, R, T>
-{
-}
-unsafe impl<'a, R: RawMutex + 'a, T: ?Sized + Send + 'a> Send for MappedMutexGuard<'a, R, T> where
- R::GuardMarker: Send
-{
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> MappedMutexGuard<'a, R, T> {
- /// Makes a new `MappedMutexGuard` for a component of the locked data.
- ///
- /// This operation cannot fail as the `MappedMutexGuard` passed
- /// in already locked the mutex.
- ///
- /// This is an associated function that needs to be
- /// used as `MappedMutexGuard::map(...)`. A method would interfere with methods of
- /// the same name on the contents of the locked data.
- #[inline]
- pub fn map<U: ?Sized, F>(s: Self, f: F) -> MappedMutexGuard<'a, R, U>
- where
- F: FnOnce(&mut T) -> &mut U,
- {
- let raw = s.raw;
- let data = f(unsafe { &mut *s.data });
- mem::forget(s);
- MappedMutexGuard {
- raw,
- data,
- marker: PhantomData,
- }
- }
-
- /// Attempts to make a new `MappedMutexGuard` for a component of the
- /// locked data. The original guard is returned if the closure returns `None`.
- ///
- /// This operation cannot fail as the `MappedMutexGuard` passed
- /// in already locked the mutex.
- ///
- /// This is an associated function that needs to be
- /// used as `MappedMutexGuard::try_map(...)`. A method would interfere with methods of
- /// the same name on the contents of the locked data.
- #[inline]
- pub fn try_map<U: ?Sized, F>(s: Self, f: F) -> Result<MappedMutexGuard<'a, R, U>, Self>
- where
- F: FnOnce(&mut T) -> Option<&mut U>,
- {
- let raw = s.raw;
- let data = match f(unsafe { &mut *s.data }) {
- Some(data) => data,
- None => return Err(s),
- };
- mem::forget(s);
- Ok(MappedMutexGuard {
- raw,
- data,
- marker: PhantomData,
- })
- }
-}
-
-impl<'a, R: RawMutexFair + 'a, T: ?Sized + 'a> MappedMutexGuard<'a, R, T> {
- /// Unlocks the mutex using a fair unlock protocol.
- ///
- /// By default, mutexes are unfair and allow the current thread to re-lock
- /// the mutex before another has the chance to acquire the lock, even if
- /// that thread has been blocked on the mutex for a long time. This is the
- /// default because it allows much higher throughput as it avoids forcing a
- /// context switch on every mutex unlock. This can result in one thread
- /// acquiring a mutex many more times than other threads.
- ///
- /// However in some cases it can be beneficial to ensure fairness by forcing
- /// the lock to pass on to a waiting thread if there is one. This is done by
- /// using this method instead of dropping the `MutexGuard` normally.
- #[inline]
- pub fn unlock_fair(s: Self) {
- // Safety: A MutexGuard always holds the lock.
- unsafe {
- s.raw.unlock_fair();
- }
- mem::forget(s);
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Deref for MappedMutexGuard<'a, R, T> {
- type Target = T;
- #[inline]
- fn deref(&self) -> &T {
- unsafe { &*self.data }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> DerefMut for MappedMutexGuard<'a, R, T> {
- #[inline]
- fn deref_mut(&mut self) -> &mut T {
- unsafe { &mut *self.data }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> Drop for MappedMutexGuard<'a, R, T> {
- #[inline]
- fn drop(&mut self) {
- // Safety: A MappedMutexGuard always holds the lock.
- unsafe {
- self.raw.unlock();
- }
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: fmt::Debug + ?Sized + 'a> fmt::Debug for MappedMutexGuard<'a, R, T> {
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- fmt::Debug::fmt(&**self, f)
- }
-}
-
-impl<'a, R: RawMutex + 'a, T: fmt::Display + ?Sized + 'a> fmt::Display
- for MappedMutexGuard<'a, R, T>
-{
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- (**self).fmt(f)
- }
-}
-
-#[cfg(feature = "owning_ref")]
-unsafe impl<'a, R: RawMutex + 'a, T: ?Sized + 'a> StableAddress for MappedMutexGuard<'a, R, T> {}
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