// Copyright 2016 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 = "owning_ref")]
use owning_ref::StableAddress;
/// Basic operations for a reader-writer lock.
///
/// Types implementing this trait can be used by `RwLock` to form a safe and
/// fully-functioning `RwLock` type.
///
/// # Safety
///
/// Implementations of this trait must ensure that the `RwLock` is actually
/// exclusive: an exclusive lock can't be acquired while an exclusive or shared
/// lock exists, and a shared lock can't be acquire while an exclusive lock
/// exists.
pub unsafe trait RawRwLock {
/// Initial value for an unlocked `RwLock`.
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 a shared lock, blocking the current thread until it is able to do so.
fn lock_shared(&self);
/// Attempts to acquire a shared lock without blocking.
fn try_lock_shared(&self) -> bool;
/// Releases a shared lock.
fn unlock_shared(&self);
/// Acquires an exclusive lock, blocking the current thread until it is able to do so.
fn lock_exclusive(&self);
/// Attempts to acquire an exclusive lock without blocking.
fn try_lock_exclusive(&self) -> bool;
/// Releases an exclusive lock.
fn unlock_exclusive(&self);
}
/// Additional methods for RwLocks 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 RawRwLockFair: RawRwLock {
/// Releases a shared lock using a fair unlock protocol.
fn unlock_shared_fair(&self);
/// Releases an exclusive lock using a fair unlock protocol.
fn unlock_exclusive_fair(&self);
/// Temporarily yields a shared lock to a waiting thread if there is one.
///
/// This method is functionally equivalent to calling `unlock_shared_fair` followed
/// by `lock_shared`, however it can be much more efficient in the case where there
/// are no waiting threads.
fn bump_shared(&self) {
self.unlock_shared_fair();
self.lock_shared();
}
/// Temporarily yields an exclusive lock to a waiting thread if there is one.
///
/// This method is functionally equivalent to calling `unlock_exclusive_fair` followed
/// by `lock_exclusive`, however it can be much more efficient in the case where there
/// are no waiting threads.
fn bump_exclusive(&self) {
self.unlock_exclusive_fair();
self.lock_exclusive();
}
}
/// Additional methods for RwLocks which support atomically downgrading an
/// exclusive lock to a shared lock.
pub unsafe trait RawRwLockDowngrade: RawRwLock {
/// Atomically downgrades an exclusive lock into a shared lock without
/// allowing any thread to take an exclusive lock in the meantime.
fn downgrade(&self);
}
/// Additional methods for RwLocks 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 RawRwLockTimed: RawRwLock {
/// Duration type used for `try_lock_for`.
type Duration;
/// Instant type used for `try_lock_until`.
type Instant;
/// Attempts to acquire a shared lock until a timeout is reached.
fn try_lock_shared_for(&self, timeout: Self::Duration) -> bool;
/// Attempts to acquire a shared lock until a timeout is reached.
fn try_lock_shared_until(&self, timeout: Self::Instant) -> bool;
/// Attempts to acquire an exclusive lock until a timeout is reached.
fn try_lock_exclusive_for(&self, timeout: Self::Duration) -> bool;
/// Attempts to acquire an exclusive lock until a timeout is reached.
fn try_lock_exclusive_until(&self, timeout: Self::Instant) -> bool;
}
/// Additional methods for RwLocks which support recursive read locks.
///
/// These are guaranteed to succeed without blocking if
/// another read lock is held at the time of the call. This allows a thread
/// to recursively lock a `RwLock`. However using this method can cause
/// writers to starve since readers no longer block if a writer is waiting
/// for the lock.
pub unsafe trait RawRwLockRecursive: RawRwLock {
/// Acquires a shared lock without deadlocking in case of a recursive lock.
fn lock_shared_recursive(&self);
/// Attempts to acquire a shared lock without deadlocking in case of a recursive lock.
fn try_lock_shared_recursive(&self) -> bool;
}
/// Additional methods for RwLocks which support recursive read locks and timeouts.
pub unsafe trait RawRwLockRecursiveTimed: RawRwLockRecursive + RawRwLockTimed {
/// Attempts to acquire a shared lock until a timeout is reached, without
/// deadlocking in case of a recursive lock.
fn try_lock_shared_recursive_for(&self, timeout: Self::Duration) -> bool;
/// Attempts to acquire a shared lock until a timeout is reached, without
/// deadlocking in case of a recursive lock.
fn try_lock_shared_recursive_until(&self, timeout: Self::Instant) -> bool;
}
/// Additional methods for RwLocks which support atomically upgrading a shared
/// lock to an exclusive lock.
///
/// This requires acquiring a special "upgradable read lock" instead of a
/// normal shared lock. There may only be one upgradable lock at any time,
/// otherwise deadlocks could occur when upgrading.
pub unsafe trait RawRwLockUpgrade: RawRwLock {
/// Acquires an upgradable lock, blocking the current thread until it is able to do so.
fn lock_upgradable(&self);
/// Attempts to acquire an upgradable lock without blocking.
fn try_lock_upgradable(&self) -> bool;
/// Releases an upgradable lock.
fn unlock_upgradable(&self);
/// Upgrades an upgradable lock to an exclusive lock.
fn upgrade(&self);
/// Attempts to upgrade an upgradable lock to an exclusive lock without
/// blocking.
fn try_upgrade(&self) -> bool;
}
/// Additional methods for RwLocks which support upgradable locks and fair
/// unlocking.
pub unsafe trait RawRwLockUpgradeFair: RawRwLockUpgrade + RawRwLockFair {
/// Releases an upgradable lock using a fair unlock protocol.
fn unlock_upgradable_fair(&self);
/// Temporarily yields an upgradable lock to a waiting thread if there is one.
///
/// This method is functionally equivalent to calling `unlock_upgradable_fair` followed
/// by `lock_upgradable`, however it can be much more efficient in the case where there
/// are no waiting threads.
fn bump_upgradable(&self) {
self.unlock_upgradable_fair();
self.lock_upgradable();
}
}
/// Additional methods for RwLocks which support upgradable locks and lock
/// downgrading.
pub unsafe trait RawRwLockUpgradeDowngrade: RawRwLockUpgrade + RawRwLockDowngrade {
/// Downgrades an upgradable lock to a shared lock.
fn downgrade_upgradable(&self);
/// Downgrades an exclusive lock to an upgradable lock.
fn downgrade_to_upgradable(&self);
}
/// Additional methods for RwLocks which support upgradable locks and locking
/// with timeouts.
pub unsafe trait RawRwLockUpgradeTimed: RawRwLockUpgrade + RawRwLockTimed {
/// Attempts to acquire an upgradable lock until a timeout is reached.
fn try_lock_upgradable_for(&self, timeout: Self::Duration) -> bool;
/// Attempts to acquire an upgradable lock until a timeout is reached.
fn try_lock_upgradable_until(&self, timeout: Self::Instant) -> bool;
/// Attempts to upgrade an upgradable lock to an exclusive lock until a
/// timeout is reached.
fn try_upgrade_for(&self, timeout: Self::Duration) -> bool;
/// Attempts to upgrade an upgradable lock to an exclusive lock until a
/// timeout is reached.
fn try_upgrade_until(&self, timeout: Self::Instant) -> bool;
}
/// A reader-writer lock
///
/// This type of lock allows a number of readers or at most one writer at any
/// point in time. The write portion of this lock typically allows modification
/// of the underlying data (exclusive access) and the read portion of this lock
/// typically allows for read-only access (shared access).
///
/// The type parameter `T` represents the data that this lock protects. It is
/// required that `T` satisfies `Send` to be shared across threads and `Sync` to
/// allow concurrent access through readers. The RAII guards returned from the
/// locking methods implement `Deref` (and `DerefMut` for the `write` methods)
/// to allow access to the contained of the lock.
pub struct RwLock<R: RawRwLock, T: ?Sized> {
raw: R,
data: UnsafeCell<T>,
}
unsafe impl<R: RawRwLock + Send, T: ?Sized + Send> Send for RwLock<R, T> {}
unsafe impl<R: RawRwLock + Sync, T: ?Sized + Send + Sync> Sync for RwLock<R, T> {}
impl<R: RawRwLock, T> RwLock<R, T> {
/// Creates a new instance of an `RwLock<T>` which is unlocked.
#[cfg(feature = "nightly")]
#[inline]
pub const fn new(val: T) -> RwLock<R, T> {
RwLock {
data: UnsafeCell::new(val),
raw: R::INIT,
}
}
/// Creates a new instance of an `RwLock<T>` which is unlocked.
#[cfg(not(feature = "nightly"))]
#[inline]
pub fn new(val: T) -> RwLock<R, T> {
RwLock {
data: UnsafeCell::new(val),
raw: R::INIT,
}
}
/// Consumes this `RwLock`, returning the underlying data.
#[inline]
#[allow(unused_unsafe)]
pub fn into_inner(self) -> T {
unsafe { self.data.into_inner() }
}
}
impl<R: RawRwLock, T: ?Sized> RwLock<R, T> {
#[inline]
fn read_guard(&self) -> RwLockReadGuard<R, T> {
RwLockReadGuard {
rwlock: self,
marker: PhantomData,
}
}
#[inline]
fn write_guard(&self) -> RwLockWriteGuard<R, T> {
RwLockWriteGuard {
rwlock: self,
marker: PhantomData,
}
}
/// Locks this `RwLock` with shared read access, blocking the current thread
/// until it can be acquired.
///
/// The calling thread will be blocked until there are no more writers which
/// hold the lock. There may be other readers currently inside the lock when
/// this method returns.
///
/// Note that attempts to recursively acquire a read lock on a `RwLock` when
/// the current thread already holds one may result in a deadlock.
///
/// Returns an RAII guard which will release this thread's shared access
/// once it is dropped.
#[inline]
pub fn read(&self) -> RwLockReadGuard<R, T> {
self.raw.lock_shared();
self.read_guard()
}
/// Attempts to acquire this `RwLock` with shared read access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned which will release the shared access
/// when it is dropped.
///
/// This function does not block.
#[inline]
pub fn try_read(&self) -> Option<RwLockReadGuard<R, T>> {
if self.raw.try_lock_shared() {
Some(self.read_guard())
} else {
None
}
}
/// Locks this `RwLock` with exclusive write access, blocking the current
/// thread until it can be acquired.
///
/// This function will not return while other writers or other readers
/// currently have access to the lock.
///
/// Returns an RAII guard which will drop the write access of this `RwLock`
/// when dropped.
#[inline]
pub fn write(&self) -> RwLockWriteGuard<R, T> {
self.raw.lock_exclusive();
self.write_guard()
}
/// Attempts to lock this `RwLock` with exclusive write access.
///
/// If the lock could not be acquired at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned which will release the lock when
/// it is dropped.
///
/// This function does not block.
#[inline]
pub fn try_write(&self) -> Option<RwLockWriteGuard<R, T>> {
if self.raw.try_lock_exclusive() {
Some(self.write_guard())
} else {
None
}
}
/// Returns a mutable reference to the underlying data.
///
/// Since this call borrows the `RwLock` 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() }
}
/// Forcibly unlocks a read lock.
///
/// This is useful when combined with `mem::forget` to hold a lock without
/// the need to maintain a `RwLockReadGuard` object alive, for example when
/// dealing with FFI.
///
/// # Safety
///
/// This method must only be called if the current thread logically owns a
/// `RwLockReadGuard` but that guard has be discarded using `mem::forget`.
/// Behavior is undefined if a rwlock is read-unlocked when not read-locked.
#[inline]
pub unsafe fn force_unlock_read(&self) {
self.raw.unlock_shared();
}
/// Forcibly unlocks a write lock.
///
/// This is useful when combined with `mem::forget` to hold a lock without
/// the need to maintain a `RwLockWriteGuard` object alive, for example when
/// dealing with FFI.
///
/// # Safety
///
/// This method must only be called if the current thread logically owns a
/// `RwLockWriteGuard` but that guard has be discarded using `mem::forget`.
/// Behavior is undefined if a rwlock is write-unlocked when not write-locked.
#[inline]
pub unsafe fn force_unlock_write(&self) {
self.raw.unlock_exclusive();
}
/// Returns the underlying raw reader-writer lock object.
///
/// Note that you will most likely need to import the `RawRwLock` trait from
/// `lock_api` to be able to call functions on the raw
/// reader-writer lock.
///
/// # Safety
///
/// This method is unsafe because it allows unlocking a mutex while
/// still holding a reference to a lock guard.
pub unsafe fn raw(&self) -> &R {
&self.raw
}
}
impl<R: RawRwLockFair, T: ?Sized> RwLock<R, T> {
/// Forcibly unlocks a read lock using a fair unlock procotol.
///
/// This is useful when combined with `mem::forget` to hold a lock without
/// the need to maintain a `RwLockReadGuard` object alive, for example when
/// dealing with FFI.
///
/// # Safety
///
/// This method must only be called if the current thread logically owns a
/// `RwLockReadGuard` but that guard has be discarded using `mem::forget`.
/// Behavior is undefined if a rwlock is read-unlocked when not read-locked.
#[inline]
pub unsafe fn force_unlock_read_fair(&self) {
self.raw.unlock_shared_fair();
}
/// Forcibly unlocks a write lock using a fair unlock procotol.
///
/// This is useful when combined with `mem::forget` to hold a lock without
/// the need to maintain a `RwLockWriteGuard` object alive, for example when
/// dealing with FFI.
///
/// # Safety
///
/// This method must only be called if the current thread logically owns a
/// `RwLockWriteGuard` but that guard has be discarded using `mem::forget`.
/// Behavior is undefined if a rwlock is write-unlocked when not write-locked.
#[inline]
pub unsafe fn force_unlock_write_fair(&self) {
self.raw.unlock_exclusive_fair();
}
}
impl<R: RawRwLockTimed, T: ?Sized> RwLock<R, T> {
/// Attempts to acquire this `RwLock` with shared read access until a timeout
/// is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the shared access when it is dropped.
#[inline]
pub fn try_read_for(&self, timeout: R::Duration) -> Option<RwLockReadGuard<R, T>> {
if self.raw.try_lock_shared_for(timeout) {
Some(self.read_guard())
} else {
None
}
}
/// Attempts to acquire this `RwLock` with shared read access until a timeout
/// is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the shared access when it is dropped.
#[inline]
pub fn try_read_until(&self, timeout: R::Instant) -> Option<RwLockReadGuard<R, T>> {
if self.raw.try_lock_shared_until(timeout) {
Some(self.read_guard())
} else {
None
}
}
/// Attempts to acquire this `RwLock` with exclusive write access until a
/// timeout is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the exclusive access when it is dropped.
#[inline]
pub fn try_write_for(&self, timeout: R::Duration) -> Option<RwLockWriteGuard<R, T>> {
if self.raw.try_lock_exclusive_for(timeout) {
Some(self.write_guard())
} else {
None
}
}
/// Attempts to acquire this `RwLock` with exclusive write access until a
/// timeout is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the exclusive access when it is dropped.
#[inline]
pub fn try_write_until(&self, timeout: R::Instant) -> Option<RwLockWriteGuard<R, T>> {
if self.raw.try_lock_exclusive_until(timeout) {
Some(self.write_guard())
} else {
None
}
}
}
impl<R: RawRwLockRecursive, T: ?Sized> RwLock<R, T> {
/// Locks this `RwLock` with shared read access, blocking the current thread
/// until it can be acquired.
///
/// The calling thread will be blocked until there are no more writers which
/// hold the lock. There may be other readers currently inside the lock when
/// this method returns.
///
/// Unlike `read`, this method is guaranteed to succeed without blocking if
/// another read lock is held at the time of the call. This allows a thread
/// to recursively lock a `RwLock`. However using this method can cause
/// writers to starve since readers no longer block if a writer is waiting
/// for the lock.
///
/// Returns an RAII guard which will release this thread's shared access
/// once it is dropped.
#[inline]
pub fn read_recursive(&self) -> RwLockReadGuard<R, T> {
self.raw.lock_shared_recursive();
self.read_guard()
}
/// Attempts to acquire this `RwLock` with shared read access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned which will release the shared access
/// when it is dropped.
///
/// This method is guaranteed to succeed if another read lock is held at the
/// time of the call. See the documentation for `read_recursive` for details.
///
/// This function does not block.
#[inline]
pub fn try_read_recursive(&self) -> Option<RwLockReadGuard<R, T>> {
if self.raw.try_lock_shared_recursive() {
Some(self.read_guard())
} else {
None
}
}
}
impl<R: RawRwLockRecursiveTimed, T: ?Sized> RwLock<R, T> {
/// Attempts to acquire this `RwLock` with shared read access until a timeout
/// is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the shared access when it is dropped.
///
/// This method is guaranteed to succeed without blocking if another read
/// lock is held at the time of the call. See the documentation for
/// `read_recursive` for details.
#[inline]
pub fn try_read_recursive_for(&self, timeout: R::Duration) -> Option<RwLockReadGuard<R, T>> {
if self.raw.try_lock_shared_recursive_for(timeout) {
Some(self.read_guard())
} else {
None
}
}
/// Attempts to acquire this `RwLock` with shared read access until a timeout
/// is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the shared access when it is dropped.
#[inline]
pub fn try_read_recursive_until(&self, timeout: R::Instant) -> Option<RwLockReadGuard<R, T>> {
if self.raw.try_lock_shared_recursive_until(timeout) {
Some(self.read_guard())
} else {
None
}
}
}
impl<R: RawRwLockUpgrade, T: ?Sized> RwLock<R, T> {
#[inline]
fn upgradable_guard(&self) -> RwLockUpgradableReadGuard<R, T> {
RwLockUpgradableReadGuard {
rwlock: self,
marker: PhantomData,
}
}
/// Locks this `RwLock` with upgradable read access, blocking the current thread
/// until it can be acquired.
///
/// The calling thread will be blocked until there are no more writers or other
/// upgradable reads which hold the lock. There may be other readers currently
/// inside the lock when this method returns.
///
/// Returns an RAII guard which will release this thread's shared access
/// once it is dropped.
#[inline]
pub fn upgradable_read(&self) -> RwLockUpgradableReadGuard<R, T> {
self.raw.lock_upgradable();
self.upgradable_guard()
}
/// Attempts to acquire this `RwLock` with upgradable read access.
///
/// If the access could not be granted at this time, then `None` is returned.
/// Otherwise, an RAII guard is returned which will release the shared access
/// when it is dropped.
///
/// This function does not block.
#[inline]
pub fn try_upgradable_read(&self) -> Option<RwLockUpgradableReadGuard<R, T>> {
if self.raw.try_lock_upgradable() {
Some(self.upgradable_guard())
} else {
None
}
}
}
impl<R: RawRwLockUpgradeTimed, T: ?Sized> RwLock<R, T> {
/// Attempts to acquire this `RwLock` with upgradable read access until a timeout
/// is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the shared access when it is dropped.
#[inline]
pub fn try_upgradable_read_for(
&self,
timeout: R::Duration,
) -> Option<RwLockUpgradableReadGuard<R, T>> {
if self.raw.try_lock_upgradable_for(timeout) {
Some(self.upgradable_guard())
} else {
None
}
}
/// Attempts to acquire this `RwLock` with upgradable read access until a timeout
/// is reached.
///
/// If the access could not be granted before the timeout expires, then
/// `None` is returned. Otherwise, an RAII guard is returned which will
/// release the shared access when it is dropped.
#[inline]
pub fn try_upgradable_read_until(
&self,
timeout: R::Instant,
) -> Option<RwLockUpgradableReadGuard<R, T>> {
if self.raw.try_lock_upgradable_until(timeout) {
Some(self.upgradable_guard())
} else {
None
}
}
}
impl<R: RawRwLock, T: ?Sized + Default> Default for RwLock<R, T> {
#[inline]
fn default() -> RwLock<R, T> {
RwLock::new(Default::default())
}
}
impl<R: RawRwLock, T> From<T> for RwLock<R, T> {
#[inline]
fn from(t: T) -> RwLock<R, T> {
RwLock::new(t)
}
}
impl<R: RawRwLock, T: ?Sized + fmt::Debug> fmt::Debug for RwLock<R, T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.try_read() {
Some(guard) => f.debug_struct("RwLock").field("data", &&*guard).finish(),
None => f.pad("RwLock { <locked> }"),
}
}
}
/// RAII structure used to release the shared read access of a lock when
/// dropped.
#[must_use]
pub struct RwLockReadGuard<'a, R: RawRwLock + 'a, T: ?Sized + 'a> {
rwlock: &'a RwLock<R, T>,
marker: PhantomData<(&'a T, R::GuardMarker)>,
}
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync for RwLockReadGuard<'a, R, T> {}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T> {
/// Returns a reference to the original reader-writer lock object.
pub fn rwlock(s: &Self) -> &'a RwLock<R, T> {
s.rwlock
}
/// Make a new `MappedRwLockReadGuard` for a component of the locked data.
///
/// This operation cannot fail as the `RwLockReadGuard` passed
/// in already locked the data.
///
/// This is an associated function that needs to be
/// used as `RwLockReadGuard::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) -> MappedRwLockReadGuard<'a, R, U>
where
F: FnOnce(&T) -> &U,
{
let raw = &s.rwlock.raw;
let data = f(unsafe { &*s.rwlock.data.get() });
mem::forget(s);
MappedRwLockReadGuard {
raw,
data,
marker: PhantomData,
}
}
/// Temporarily unlocks the `RwLock` to execute the given function.
///
/// The `RwLock` is unlocked a fair unlock protocol.
///
/// This is safe because `&mut` guarantees that there exist no other
/// references to the data protected by the `RwLock`.
#[inline]
pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
where
F: FnOnce() -> U,
{
s.rwlock.raw.unlock_shared();
defer!(s.rwlock.raw.lock_shared());
f()
}
}
impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> RwLockReadGuard<'a, R, T> {
/// Unlocks the `RwLock` using a fair unlock protocol.
///
/// By default, `RwLock` is unfair and allow the current thread to re-lock
/// the `RwLock` before another has the chance to acquire the lock, even if
/// that thread has been blocked on the `RwLock` for a long time. This is
/// the default because it allows much higher throughput as it avoids
/// forcing a context switch on every `RwLock` unlock. This can result in one
/// thread acquiring a `RwLock` 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 `RwLockReadGuard` normally.
#[inline]
pub fn unlock_fair(s: Self) {
s.rwlock.raw.unlock_shared_fair();
mem::forget(s);
}
/// Temporarily unlocks the `RwLock` to execute the given function.
///
/// The `RwLock` is unlocked a fair unlock protocol.
///
/// This is safe because `&mut` guarantees that there exist no other
/// references to the data protected by the `RwLock`.
#[inline]
pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
where
F: FnOnce() -> U,
{
s.rwlock.raw.unlock_shared_fair();
defer!(s.rwlock.raw.lock_shared());
f()
}
/// Temporarily yields the `RwLock` to a waiting thread if there is one.
///
/// This method is functionally equivalent to calling `unlock_fair` followed
/// by `read`, however it can be much more efficient in the case where there
/// are no waiting threads.
#[inline]
pub fn bump(s: &mut Self) {
s.rwlock.raw.bump_shared();
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for RwLockReadGuard<'a, R, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
unsafe { &*self.rwlock.data.get() }
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for RwLockReadGuard<'a, R, T> {
#[inline]
fn drop(&mut self) {
self.rwlock.raw.unlock_shared();
}
}
impl<'a, R: RawRwLockRecursive + 'a, T: ?Sized + 'a> Clone for RwLockReadGuard<'a, R, T> {
#[inline]
fn clone(&self) -> Self {
self.rwlock.raw.lock_shared_recursive();
RwLockReadGuard {
rwlock: self.rwlock,
marker: PhantomData,
}
}
}
#[cfg(feature = "owning_ref")]
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress for RwLockReadGuard<'a, R, T> {}
/// RAII structure used to release the exclusive write access of a lock when
/// dropped.
#[must_use]
pub struct RwLockWriteGuard<'a, R: RawRwLock + 'a, T: ?Sized + 'a> {
rwlock: &'a RwLock<R, T>,
marker: PhantomData<(&'a mut T, R::GuardMarker)>,
}
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync for RwLockWriteGuard<'a, R, T> {}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> {
/// Returns a reference to the original reader-writer lock object.
pub fn rwlock(s: &Self) -> &'a RwLock<R, T> {
s.rwlock
}
/// Make a new `MappedRwLockWriteGuard` for a component of the locked data.
///
/// This operation cannot fail as the `RwLockWriteGuard` passed
/// in already locked the data.
///
/// This is an associated function that needs to be
/// used as `RwLockWriteGuard::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>(orig: Self, f: F) -> MappedRwLockWriteGuard<'a, R, U>
where
F: FnOnce(&mut T) -> &mut U,
{
let raw = &orig.rwlock.raw;
let data = f(unsafe { &mut *orig.rwlock.data.get() });
mem::forget(orig);
MappedRwLockWriteGuard {
raw,
data,
marker: PhantomData,
}
}
/// Temporarily unlocks the `RwLock` to execute the given function.
///
/// This is safe because `&mut` guarantees that there exist no other
/// references to the data protected by the `RwLock`.
#[inline]
pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
where
F: FnOnce() -> U,
{
s.rwlock.raw.unlock_exclusive();
defer!(s.rwlock.raw.lock_exclusive());
f()
}
}
impl<'a, R: RawRwLockDowngrade + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> {
/// Atomically downgrades a write lock into a read lock without allowing any
/// writers to take exclusive access of the lock in the meantime.
///
/// Note that if there are any writers currently waiting to take the lock
/// then other readers may not be able to acquire the lock even if it was
/// downgraded.
pub fn downgrade(s: Self) -> RwLockReadGuard<'a, R, T> {
s.rwlock.raw.downgrade();
let rwlock = s.rwlock;
mem::forget(s);
RwLockReadGuard {
rwlock,
marker: PhantomData,
}
}
}
impl<'a, R: RawRwLockUpgradeDowngrade + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> {
/// Atomically downgrades a write lock into an upgradable read lock without allowing any
/// writers to take exclusive access of the lock in the meantime.
///
/// Note that if there are any writers currently waiting to take the lock
/// then other readers may not be able to acquire the lock even if it was
/// downgraded.
pub fn downgrade_to_upgradable(s: Self) -> RwLockUpgradableReadGuard<'a, R, T> {
s.rwlock.raw.downgrade_to_upgradable();
let rwlock = s.rwlock;
mem::forget(s);
RwLockUpgradableReadGuard {
rwlock,
marker: PhantomData,
}
}
}
impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> RwLockWriteGuard<'a, R, T> {
/// Unlocks the `RwLock` using a fair unlock protocol.
///
/// By default, `RwLock` is unfair and allow the current thread to re-lock
/// the `RwLock` before another has the chance to acquire the lock, even if
/// that thread has been blocked on the `RwLock` for a long time. This is
/// the default because it allows much higher throughput as it avoids
/// forcing a context switch on every `RwLock` unlock. This can result in one
/// thread acquiring a `RwLock` 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 `RwLockWriteGuard` normally.
#[inline]
pub fn unlock_fair(s: Self) {
s.rwlock.raw.unlock_exclusive_fair();
mem::forget(s);
}
/// Temporarily unlocks the `RwLock` to execute the given function.
///
/// The `RwLock` is unlocked a fair unlock protocol.
///
/// This is safe because `&mut` guarantees that there exist no other
/// references to the data protected by the `RwLock`.
#[inline]
pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
where
F: FnOnce() -> U,
{
s.rwlock.raw.unlock_exclusive_fair();
defer!(s.rwlock.raw.lock_exclusive());
f()
}
/// Temporarily yields the `RwLock` to a waiting thread if there is one.
///
/// This method is functionally equivalent to calling `unlock_fair` followed
/// by `write`, however it can be much more efficient in the case where there
/// are no waiting threads.
#[inline]
pub fn bump(s: &mut Self) {
s.rwlock.raw.bump_exclusive();
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for RwLockWriteGuard<'a, R, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
unsafe { &*self.rwlock.data.get() }
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> DerefMut for RwLockWriteGuard<'a, R, T> {
#[inline]
fn deref_mut(&mut self) -> &mut T {
unsafe { &mut *self.rwlock.data.get() }
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for RwLockWriteGuard<'a, R, T> {
#[inline]
fn drop(&mut self) {
self.rwlock.raw.unlock_exclusive();
}
}
#[cfg(feature = "owning_ref")]
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress for RwLockWriteGuard<'a, R, T> {}
/// RAII structure used to release the upgradable read access of a lock when
/// dropped.
#[must_use]
pub struct RwLockUpgradableReadGuard<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> {
rwlock: &'a RwLock<R, T>,
marker: PhantomData<(&'a T, R::GuardMarker)>,
}
unsafe impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + Sync + 'a> Sync
for RwLockUpgradableReadGuard<'a, R, T>
{}
impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> {
/// Returns a reference to the original reader-writer lock object.
pub fn rwlock(s: &Self) -> &'a RwLock<R, T> {
s.rwlock
}
/// Temporarily unlocks the `RwLock` to execute the given function.
///
/// This is safe because `&mut` guarantees that there exist no other
/// references to the data protected by the `RwLock`.
#[inline]
pub fn unlocked<F, U>(s: &mut Self, f: F) -> U
where
F: FnOnce() -> U,
{
s.rwlock.raw.unlock_upgradable();
defer!(s.rwlock.raw.lock_upgradable());
f()
}
/// Atomically upgrades an upgradable read lock lock into a exclusive write lock,
/// blocking the current thread until it can be aquired.
pub fn upgrade(s: Self) -> RwLockWriteGuard<'a, R, T> {
s.rwlock.raw.upgrade();
let rwlock = s.rwlock;
mem::forget(s);
RwLockWriteGuard {
rwlock,
marker: PhantomData,
}
}
/// Tries to atomically upgrade an upgradable read lock into a exclusive write lock.
///
/// If the access could not be granted at this time, then the current guard is returned.
pub fn try_upgrade(s: Self) -> Result<RwLockWriteGuard<'a, R, T>, Self> {
if s.rwlock.raw.try_upgrade() {
let rwlock = s.rwlock;
mem::forget(s);
Ok(RwLockWriteGuard {
rwlock,
marker: PhantomData,
})
} else {
Err(s)
}
}
}
impl<'a, R: RawRwLockUpgradeFair + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> {
/// Unlocks the `RwLock` using a fair unlock protocol.
///
/// By default, `RwLock` is unfair and allow the current thread to re-lock
/// the `RwLock` before another has the chance to acquire the lock, even if
/// that thread has been blocked on the `RwLock` for a long time. This is
/// the default because it allows much higher throughput as it avoids
/// forcing a context switch on every `RwLock` unlock. This can result in one
/// thread acquiring a `RwLock` 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 `RwLockUpgradableReadGuard` normally.
#[inline]
pub fn unlock_fair(s: Self) {
s.rwlock.raw.unlock_upgradable_fair();
mem::forget(s);
}
/// Temporarily unlocks the `RwLock` to execute the given function.
///
/// The `RwLock` is unlocked a fair unlock protocol.
///
/// This is safe because `&mut` guarantees that there exist no other
/// references to the data protected by the `RwLock`.
#[inline]
pub fn unlocked_fair<F, U>(s: &mut Self, f: F) -> U
where
F: FnOnce() -> U,
{
s.rwlock.raw.unlock_upgradable_fair();
defer!(s.rwlock.raw.lock_upgradable());
f()
}
/// Temporarily yields the `RwLock` to a waiting thread if there is one.
///
/// This method is functionally equivalent to calling `unlock_fair` followed
/// by `upgradable_read`, however it can be much more efficient in the case where there
/// are no waiting threads.
#[inline]
pub fn bump(s: &mut Self) {
s.rwlock.raw.bump_upgradable();
}
}
impl<'a, R: RawRwLockUpgradeDowngrade + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> {
/// Atomically downgrades an upgradable read lock lock into a shared read lock
/// without allowing any writers to take exclusive access of the lock in the
/// meantime.
///
/// Note that if there are any writers currently waiting to take the lock
/// then other readers may not be able to acquire the lock even if it was
/// downgraded.
pub fn downgrade(s: Self) -> RwLockReadGuard<'a, R, T> {
s.rwlock.raw.downgrade_upgradable();
let rwlock = s.rwlock;
mem::forget(s);
RwLockReadGuard {
rwlock,
marker: PhantomData,
}
}
}
impl<'a, R: RawRwLockUpgradeTimed + 'a, T: ?Sized + 'a> RwLockUpgradableReadGuard<'a, R, T> {
/// Tries to atomically upgrade an upgradable read lock into a exclusive
/// write lock, until a timeout is reached.
///
/// If the access could not be granted before the timeout expires, then
/// the current guard is returned.
pub fn try_upgrade_for(
s: Self,
timeout: R::Duration,
) -> Result<RwLockWriteGuard<'a, R, T>, Self> {
if s.rwlock.raw.try_upgrade_for(timeout) {
let rwlock = s.rwlock;
mem::forget(s);
Ok(RwLockWriteGuard {
rwlock,
marker: PhantomData,
})
} else {
Err(s)
}
}
/// Tries to atomically upgrade an upgradable read lock into a exclusive
/// write lock, until a timeout is reached.
///
/// If the access could not be granted before the timeout expires, then
/// the current guard is returned.
#[inline]
pub fn try_upgrade_until(
s: Self,
timeout: R::Instant,
) -> Result<RwLockWriteGuard<'a, R, T>, Self> {
if s.rwlock.raw.try_upgrade_until(timeout) {
let rwlock = s.rwlock;
mem::forget(s);
Ok(RwLockWriteGuard {
rwlock,
marker: PhantomData,
})
} else {
Err(s)
}
}
}
impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> Deref for RwLockUpgradableReadGuard<'a, R, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
unsafe { &*self.rwlock.data.get() }
}
}
impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> Drop for RwLockUpgradableReadGuard<'a, R, T> {
#[inline]
fn drop(&mut self) {
self.rwlock.raw.unlock_upgradable();
}
}
#[cfg(feature = "owning_ref")]
unsafe impl<'a, R: RawRwLockUpgrade + 'a, T: ?Sized + 'a> StableAddress
for RwLockUpgradableReadGuard<'a, R, T>
{}
/// An RAII read lock guard returned by `RwLockReadGuard::map`, which can point to a
/// subfield of the protected data.
///
/// The main difference between `MappedRwLockReadGuard` and `RwLockReadGuard` 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.
#[must_use]
pub struct MappedRwLockReadGuard<'a, R: RawRwLock + 'a, T: ?Sized + 'a> {
raw: &'a R,
data: *const T,
marker: PhantomData<&'a T>,
}
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync for MappedRwLockReadGuard<'a, R, T> {}
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Send for MappedRwLockReadGuard<'a, R, T> where
R::GuardMarker: Send
{}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> MappedRwLockReadGuard<'a, R, T> {
/// Make a new `MappedRwLockReadGuard` for a component of the locked data.
///
/// This operation cannot fail as the `MappedRwLockReadGuard` passed
/// in already locked the data.
///
/// This is an associated function that needs to be
/// used as `MappedRwLockReadGuard::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) -> MappedRwLockReadGuard<'a, R, U>
where
F: FnOnce(&T) -> &U,
{
let raw = s.raw;
let data = f(unsafe { &*s.data });
mem::forget(s);
MappedRwLockReadGuard {
raw,
data,
marker: PhantomData,
}
}
}
impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> MappedRwLockReadGuard<'a, R, T> {
/// Unlocks the `RwLock` using a fair unlock protocol.
///
/// By default, `RwLock` is unfair and allow the current thread to re-lock
/// the `RwLock` before another has the chance to acquire the lock, even if
/// that thread has been blocked on the `RwLock` for a long time. This is
/// the default because it allows much higher throughput as it avoids
/// forcing a context switch on every `RwLock` unlock. This can result in one
/// thread acquiring a `RwLock` 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 `MappedRwLockReadGuard` normally.
#[inline]
pub fn unlock_fair(s: Self) {
s.raw.unlock_shared_fair();
mem::forget(s);
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for MappedRwLockReadGuard<'a, R, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
unsafe { &*self.data }
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for MappedRwLockReadGuard<'a, R, T> {
#[inline]
fn drop(&mut self) {
self.raw.unlock_shared();
}
}
impl<'a, R: RawRwLockRecursive + 'a, T: ?Sized + 'a> Clone for MappedRwLockReadGuard<'a, R, T> {
#[inline]
fn clone(&self) -> Self {
self.raw.lock_shared_recursive();
MappedRwLockReadGuard {
raw: self.raw,
data: self.data,
marker: PhantomData,
}
}
}
#[cfg(feature = "owning_ref")]
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress
for MappedRwLockReadGuard<'a, R, T>
{}
/// An RAII write lock guard returned by `RwLockWriteGuard::map`, which can point to a
/// subfield of the protected data.
///
/// The main difference between `MappedRwLockWriteGuard` and `RwLockWriteGuard` 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.
#[must_use]
pub struct MappedRwLockWriteGuard<'a, R: RawRwLock + 'a, T: ?Sized + 'a> {
raw: &'a R,
data: *mut T,
marker: PhantomData<&'a mut T>,
}
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + Sync + 'a> Sync
for MappedRwLockWriteGuard<'a, R, T>
{}
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Send for MappedRwLockWriteGuard<'a, R, T> where
R::GuardMarker: Send
{}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> MappedRwLockWriteGuard<'a, R, T> {
/// Make a new `MappedRwLockWriteGuard` for a component of the locked data.
///
/// This operation cannot fail as the `MappedRwLockWriteGuard` passed
/// in already locked the data.
///
/// This is an associated function that needs to be
/// used as `MappedRwLockWriteGuard::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>(orig: Self, f: F) -> MappedRwLockWriteGuard<'a, R, U>
where
F: FnOnce(&mut T) -> &mut U,
{
let raw = orig.raw;
let data = f(unsafe { &mut *orig.data });
mem::forget(orig);
MappedRwLockWriteGuard {
raw,
data,
marker: PhantomData,
}
}
}
impl<'a, R: RawRwLockDowngrade + 'a, T: ?Sized + 'a> MappedRwLockWriteGuard<'a, R, T> {
/// Atomically downgrades a write lock into a read lock without allowing any
/// writers to take exclusive access of the lock in the meantime.
///
/// Note that if there are any writers currently waiting to take the lock
/// then other readers may not be able to acquire the lock even if it was
/// downgraded.
pub fn downgrade(s: Self) -> MappedRwLockReadGuard<'a, R, T> {
s.raw.downgrade();
let raw = s.raw;
let data = s.data;
mem::forget(s);
MappedRwLockReadGuard {
raw,
data,
marker: PhantomData,
}
}
}
impl<'a, R: RawRwLockFair + 'a, T: ?Sized + 'a> MappedRwLockWriteGuard<'a, R, T> {
/// Unlocks the `RwLock` using a fair unlock protocol.
///
/// By default, `RwLock` is unfair and allow the current thread to re-lock
/// the `RwLock` before another has the chance to acquire the lock, even if
/// that thread has been blocked on the `RwLock` for a long time. This is
/// the default because it allows much higher throughput as it avoids
/// forcing a context switch on every `RwLock` unlock. This can result in one
/// thread acquiring a `RwLock` 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 `MappedRwLockWriteGuard` normally.
#[inline]
pub fn unlock_fair(s: Self) {
s.raw.unlock_exclusive_fair();
mem::forget(s);
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Deref for MappedRwLockWriteGuard<'a, R, T> {
type Target = T;
#[inline]
fn deref(&self) -> &T {
unsafe { &*self.data }
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> DerefMut for MappedRwLockWriteGuard<'a, R, T> {
#[inline]
fn deref_mut(&mut self) -> &mut T {
unsafe { &mut *self.data }
}
}
impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> Drop for MappedRwLockWriteGuard<'a, R, T> {
#[inline]
fn drop(&mut self) {
self.raw.unlock_exclusive();
}
}
#[cfg(feature = "owning_ref")]
unsafe impl<'a, R: RawRwLock + 'a, T: ?Sized + 'a> StableAddress
for MappedRwLockWriteGuard<'a, R, T>
{}