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add nonpoison::condvar implementation

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Adds the equivalent `nonpoison` types to the `poison::condvar` module.
These types and implementations are gated under the `nonpoison_condvar`
feature gate.

Signed-off-by: Connor Tsui <connor.tsui20@gmail.com>
This commit is contained in:
Connor Tsui 2025-08-23 09:14:51 -04:00
parent 5b6ceb58f8
commit eaf7fd2fed
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3 changed files with 524 additions and 2 deletions
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3
library/std/src/sync/nonpoison.rs
View file

@ -29,6 +29,8 @@ impl fmt::Display for WouldBlock {
}
}
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub use self::condvar::{Condvar, WaitTimeoutResult};
#[unstable(feature = "mapped_lock_guards", issue = "117108")]
pub use self::mutex::MappedMutexGuard;
#[unstable(feature = "nonpoison_mutex", issue = "134645")]
@ -38,5 +40,6 @@ pub use self::rwlock::{MappedRwLockReadGuard, MappedRwLockWriteGuard};
#[unstable(feature = "nonpoison_rwlock", issue = "134645")]
pub use self::rwlock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
mod condvar;
mod mutex;
mod rwlock;

516
library/std/src/sync/nonpoison/condvar.rs Normal file
View file

@ -0,0 +1,516 @@
use crate::fmt;
use crate::sync::nonpoison::{MutexGuard, mutex};
use crate::sys::sync as sys;
use crate::time::{Duration, Instant};
/// A type indicating whether a timed wait on a condition variable returned
/// due to a time out or not.
///
/// It is returned by the [`wait_timeout`] method.
///
/// [`wait_timeout`]: Condvar::wait_timeout
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub struct WaitTimeoutResult(bool);
// FIXME(nonpoison_condvar) this type is duplicated in `poison`. How do we share types that are
// poison-agnostic?
impl WaitTimeoutResult {
/// Returns `true` if the wait was known to have timed out.
///
/// # Examples
///
/// This example spawns a thread which will sleep 20 milliseconds before
/// updating a boolean value and then notifying the condvar.
///
/// The main thread will wait with a 10 millisecond timeout on the condvar
/// and will leave the loop upon timeout.
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
/// use std::time::Duration;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// # let handle =
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
///
/// // Let's wait 20 milliseconds before notifying the condvar.
/// thread::sleep(Duration::from_millis(20));
///
/// let mut started = lock.lock();
/// // We update the boolean value.
/// *started = true;
/// cvar.notify_one();
/// });
///
/// // Wait for the thread to start up.
/// let (lock, cvar) = &*pair;
/// loop {
/// // Let's put a timeout on the condvar's wait.
/// let result = cvar.wait_timeout(lock.lock(), Duration::from_millis(10));
/// // 10 milliseconds have passed.
/// if result.1.timed_out() {
/// // timed out now and we can leave.
/// break
/// }
/// }
/// # // Prevent leaks for Miri.
/// # let _ = handle.join();
/// ```
#[must_use]
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn timed_out(&self) -> bool {
self.0
}
}
/// A Condition Variable
///
/// For more information about condition variables, check out the documentation for the poisoning
/// variant of this type at [`poison::Condvar`].
///
/// # Examples
///
/// Note that this `Condvar` does **not** propagate information about threads that panic while
/// holding a lock. If you need this functionality, see [`poison::Mutex`] and [`poison::Condvar`].
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// // Inside of our lock, spawn a new thread, and then wait for it to start.
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut started = lock.lock();
/// *started = true;
/// // We notify the condvar that the value has changed.
/// cvar.notify_one();
/// });
///
/// // Wait for the thread to start up.
/// let (lock, cvar) = &*pair;
/// let mut started = lock.lock();
/// while !*started {
/// started = cvar.wait(started);
/// }
/// ```
///
/// [`poison::Mutex`]: crate::sync::poison::Mutex
/// [`poison::Condvar`]: crate::sync::poison::Condvar
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub struct Condvar {
inner: sys::Condvar,
}
impl Condvar {
/// Creates a new condition variable which is ready to be waited on and
/// notified.
///
/// # Examples
///
/// ```
/// use std::sync::Condvar;
///
/// let condvar = Condvar::new();
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
#[must_use]
#[inline]
pub const fn new() -> Condvar {
Condvar { inner: sys::Condvar::new() }
}
/// Blocks the current thread until this condition variable receives a
/// notification.
///
/// This function will atomically unlock the mutex specified (represented by
/// `guard`) and block the current thread. This means that any calls
/// to [`notify_one`] or [`notify_all`] which happen logically after the
/// mutex is unlocked are candidates to wake this thread up. When this
/// function call returns, the lock specified will have been re-acquired.
///
/// Note that this function is susceptible to spurious wakeups. Condition
/// variables normally have a boolean predicate associated with them, and
/// the predicate must always be checked each time this function returns to
/// protect against spurious wakeups.
///
/// # Panics
///
/// This function may [`panic!`] if it is used with more than one mutex
/// over time.
///
/// [`notify_one`]: Self::notify_one
/// [`notify_all`]: Self::notify_all
///
/// # Examples
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut started = lock.lock();
/// *started = true;
/// // We notify the condvar that the value has changed.
/// cvar.notify_one();
/// });
///
/// // Wait for the thread to start up.
/// let (lock, cvar) = &*pair;
/// let mut started = lock.lock();
/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
/// while !*started {
/// started = cvar.wait(started);
/// }
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn wait<'a, T>(&self, guard: MutexGuard<'a, T>) -> MutexGuard<'a, T> {
unsafe {
let lock = mutex::guard_lock(&guard);
self.inner.wait(lock);
}
guard
}
/// Blocks the current thread until the provided condition becomes false.
///
/// `condition` is checked immediately; if not met (returns `true`), this
/// will [`wait`] for the next notification then check again. This repeats
/// until `condition` returns `false`, in which case this function returns.
///
/// This function will atomically unlock the mutex specified (represented by
/// `guard`) and block the current thread. This means that any calls
/// to [`notify_one`] or [`notify_all`] which happen logically after the
/// mutex is unlocked are candidates to wake this thread up. When this
/// function call returns, the lock specified will have been re-acquired.
///
/// [`wait`]: Self::wait
/// [`notify_one`]: Self::notify_one
/// [`notify_all`]: Self::notify_all
///
/// # Examples
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
///
/// let pair = Arc::new((Mutex::new(true), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut pending = lock.lock();
/// *pending = false;
/// // We notify the condvar that the value has changed.
/// cvar.notify_one();
/// });
///
/// // Wait for the thread to start up.
/// let (lock, cvar) = &*pair;
/// // As long as the value inside the `Mutex<bool>` is `true`, we wait.
/// let _guard = cvar.wait_while(lock.lock(), |pending| { *pending });
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn wait_while<'a, T, F>(
&self,
mut guard: MutexGuard<'a, T>,
mut condition: F,
) -> MutexGuard<'a, T>
where
F: FnMut(&mut T) -> bool,
{
while condition(&mut *guard) {
guard = self.wait(guard);
}
guard
}
/// Waits on this condition variable for a notification, timing out after a
/// specified duration.
///
/// The semantics of this function are equivalent to [`wait`] except that
/// the thread will be blocked for roughly no longer than `dur`. This
/// method should not be used for precise timing due to anomalies such as
/// preemption or platform differences that might not cause the maximum
/// amount of time waited to be precisely `dur`.
///
/// Note that the best effort is made to ensure that the time waited is
/// measured with a monotonic clock, and not affected by the changes made to
/// the system time. This function is susceptible to spurious wakeups.
/// Condition variables normally have a boolean predicate associated with
/// them, and the predicate must always be checked each time this function
/// returns to protect against spurious wakeups. Additionally, it is
/// typically desirable for the timeout to not exceed some duration in
/// spite of spurious wakes, thus the sleep-duration is decremented by the
/// amount slept. Alternatively, use the `wait_timeout_while` method
/// to wait with a timeout while a predicate is true.
///
/// The returned [`WaitTimeoutResult`] value indicates if the timeout is
/// known to have elapsed.
///
/// Like [`wait`], the lock specified will be re-acquired when this function
/// returns, regardless of whether the timeout elapsed or not.
///
/// [`wait`]: Self::wait
/// [`wait_timeout_while`]: Self::wait_timeout_while
///
/// # Examples
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
/// use std::time::Duration;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut started = lock.lock();
/// *started = true;
/// // We notify the condvar that the value has changed.
/// cvar.notify_one();
/// });
///
/// // wait for the thread to start up
/// let (lock, cvar) = &*pair;
/// let mut started = lock.lock();
/// // as long as the value inside the `Mutex<bool>` is `false`, we wait
/// loop {
/// let result = cvar.wait_timeout(started, Duration::from_millis(10));
/// // 10 milliseconds have passed, or maybe the value changed!
/// started = result.0;
/// if *started == true {
/// // We received the notification and the value has been updated, we can leave.
/// break
/// }
/// }
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn wait_timeout<'a, T>(
&self,
guard: MutexGuard<'a, T>,
dur: Duration,
) -> (MutexGuard<'a, T>, WaitTimeoutResult) {
let success = unsafe {
let lock = mutex::guard_lock(&guard);
self.inner.wait_timeout(lock, dur)
};
(guard, WaitTimeoutResult(!success))
}
/// Waits on this condition variable for a notification, timing out after a
/// specified duration.
///
/// The semantics of this function are equivalent to [`wait_while`] except
/// that the thread will be blocked for roughly no longer than `dur`. This
/// method should not be used for precise timing due to anomalies such as
/// preemption or platform differences that might not cause the maximum
/// amount of time waited to be precisely `dur`.
///
/// Note that the best effort is made to ensure that the time waited is
/// measured with a monotonic clock, and not affected by the changes made to
/// the system time.
///
/// The returned [`WaitTimeoutResult`] value indicates if the timeout is
/// known to have elapsed without the condition being met.
///
/// Like [`wait_while`], the lock specified will be re-acquired when this
/// function returns, regardless of whether the timeout elapsed or not.
///
/// [`wait_while`]: Self::wait_while
/// [`wait_timeout`]: Self::wait_timeout
///
/// # Examples
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
/// use std::time::Duration;
///
/// let pair = Arc::new((Mutex::new(true), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut pending = lock.lock();
/// *pending = false;
/// // We notify the condvar that the value has changed.
/// cvar.notify_one();
/// });
///
/// // wait for the thread to start up
/// let (lock, cvar) = &*pair;
/// let result = cvar.wait_timeout_while(
/// lock.lock(),
/// Duration::from_millis(100),
/// |&mut pending| pending,
/// );
/// if result.1.timed_out() {
/// // timed-out without the condition ever evaluating to false.
/// }
/// // access the locked mutex via result.0
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn wait_timeout_while<'a, T, F>(
&self,
mut guard: MutexGuard<'a, T>,
dur: Duration,
mut condition: F,
) -> (MutexGuard<'a, T>, WaitTimeoutResult)
where
F: FnMut(&mut T) -> bool,
{
let start = Instant::now();
loop {
if !condition(&mut *guard) {
return (guard, WaitTimeoutResult(false));
}
let timeout = match dur.checked_sub(start.elapsed()) {
Some(timeout) => timeout,
None => return (guard, WaitTimeoutResult(true)),
};
guard = self.wait_timeout(guard, timeout).0;
}
}
/// Wakes up one blocked thread on this condvar.
///
/// If there is a blocked thread on this condition variable, then it will
/// be woken up from its call to [`wait`] or [`wait_timeout`]. Calls to
/// `notify_one` are not buffered in any way.
///
/// To wake up all threads, see [`notify_all`].
///
/// [`wait`]: Self::wait
/// [`wait_timeout`]: Self::wait_timeout
/// [`notify_all`]: Self::notify_all
///
/// # Examples
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut started = lock.lock();
/// *started = true;
/// // We notify the condvar that the value has changed.
/// cvar.notify_one();
/// });
///
/// // Wait for the thread to start up.
/// let (lock, cvar) = &*pair;
/// let mut started = lock.lock();
/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
/// while !*started {
/// started = cvar.wait(started);
/// }
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn notify_one(&self) {
self.inner.notify_one()
}
/// Wakes up all blocked threads on this condvar.
///
/// This method will ensure that any current waiters on the condition
/// variable are awoken. Calls to `notify_all()` are not buffered in any
/// way.
///
/// To wake up only one thread, see [`notify_one`].
///
/// [`notify_one`]: Self::notify_one
///
/// # Examples
///
/// ```
/// #![feature(nonpoison_mutex)]
/// #![feature(nonpoison_condvar)]
///
/// use std::sync::nonpoison::{Mutex, Condvar};
/// use std::sync::Arc;
/// use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair2 = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (lock, cvar) = &*pair2;
/// let mut started = lock.lock();
/// *started = true;
/// // We notify the condvar that the value has changed.
/// cvar.notify_all();
/// });
///
/// // Wait for the thread to start up.
/// let (lock, cvar) = &*pair;
/// let mut started = lock.lock();
/// // As long as the value inside the `Mutex<bool>` is `false`, we wait.
/// while !*started {
/// started = cvar.wait(started);
/// }
/// ```
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
pub fn notify_all(&self) {
self.inner.notify_all()
}
}
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
impl fmt::Debug for Condvar {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Condvar").finish_non_exhaustive()
}
}
#[unstable(feature = "nonpoison_condvar", issue = "134645")]
impl Default for Condvar {
/// Creates a `Condvar` which is ready to be waited on and notified.
fn default() -> Condvar {
Condvar::new()
}
}

7
library/std/src/sync/nonpoison/mutex.rs
View file

@ -114,7 +114,6 @@ impl<T: ?Sized> !Send for MutexGuard<'_, T> {}
#[unstable(feature = "nonpoison_mutex", issue = "134645")]
unsafe impl<T: ?Sized + Sync> Sync for MutexGuard<'_, T> {}
// FIXME(nonpoison_condvar): Use this link instead: [`Condvar`]: crate::sync::nonpoison::Condvar
/// An RAII mutex guard returned by `MutexGuard::map`, which can point to a
/// subfield of the protected data. When this structure is dropped (falls out
/// of scope), the lock will be unlocked.
@ -131,7 +130,7 @@ unsafe impl<T: ?Sized + Sync> Sync for MutexGuard<'_, T> {}
///
/// [`map`]: MutexGuard::map
/// [`filter_map`]: MutexGuard::filter_map
/// [`Condvar`]: crate::sync::Condvar
/// [`Condvar`]: crate::sync::nonpoison::Condvar
#[must_use = "if unused the Mutex will immediately unlock"]
#[must_not_suspend = "holding a MappedMutexGuard across suspend \
points can cause deadlocks, delays, \
@ -458,6 +457,10 @@ impl<T: ?Sized + fmt::Display> fmt::Display for MutexGuard<'_, T> {
}
}
pub fn guard_lock<'a, T: ?Sized>(guard: &MutexGuard<'a, T>) -> &'a sys::Mutex {
&guard.lock.inner
}
impl<'a, T: ?Sized> MutexGuard<'a, T> {
/// Makes a [`MappedMutexGuard`] for a component of the borrowed data, e.g.
/// an enum variant.