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// SPDX-License-Identifier: MIT OR Apache-2.0
use super::Instant;
use super::{Condvar, WaitTimeoutResult};
use crate::Guard;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
impl Condvar {
/// Waits by spinning for a notification from this condition variable.
///
/// This method will atomically unlock the mutex specified by the guard and
/// spin in a tight loop while waiting to be notified. When a notification is received, the
/// mutex will be re-acquired before returning.
///
/// While this ensures the wait completes, it consumes CPU cycles. Use this
/// when you know notifications will arrive quickly, or when blocking is not
/// possible (e.g., WASM main thread).
///
/// # Spurious Wakeups
///
/// This method may return spuriously (without a notification). Always use it
/// in a loop that checks the condition.
///
/// # Examples
///
/// ```
/// # // std::thread::spawn panics on wasm32
/// # if cfg!(target_arch = "wasm32") { return; }
/// use wasm_safe_mutex::{Mutex, condvar::Condvar};
/// use std::sync::Arc;
/// # use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair_clone = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (mutex, condvar) = &*pair_clone;
/// let mut ready = mutex.lock_sync();
/// *ready = true;
/// drop(ready);
/// condvar.notify_one();
/// });
///
/// let (mutex, condvar) = &*pair;
/// let mut ready = mutex.lock_sync();
/// while !*ready {
/// ready = condvar.wait_spin(ready);
/// }
/// assert!(*ready);
/// ```
pub fn wait_spin<'a, T>(&self, guard: Guard<'a, T>) -> Guard<'a, T> {
let wake = Arc::new(AtomicBool::new(false));
let mutex = guard.mutex;
//insert into wait queue
self.waiting_spin_threads.with_mut(|e| e.push(wake.clone()));
// Release the mutex
drop(guard);
while !wake.load(Ordering::Acquire) {
std::hint::spin_loop();
}
// Re-acquire the mutex before returning
mutex.lock_sync()
}
/// Waits by spinning while the predicate remains `true`.
///
/// This method will atomically unlock the mutex specified by the guard and
/// spin in a tight loop as long as the `condition` closure returns `true`.
///
/// # Platform Behavior
///
/// - **All Platforms**: Uses a busy loop (spinning) to wait. This consumes CPU
/// cycles but works in all environments, including WASM main thread.
///
/// # Predicate
///
/// The `condition` closure is called:
/// 1. Before waiting (if it returns `false`, the method returns immediately)
/// 2. After each notification (to check if we should keep waiting)
/// 3. After spurious wakeups (to ensure we don't return prematurely)
///
/// # Spurious Wakeups
///
/// This method automatically handles spurious wakeups by re-checking the condition.
/// You do not need to loop around this call.
///
/// # Examples
///
/// ```
/// # // std::thread::spawn panics on wasm32
/// # if cfg!(target_arch = "wasm32") { return; }
/// use wasm_safe_mutex::{Mutex, condvar::Condvar};
/// use std::sync::Arc;
/// # use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair_clone = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (mutex, condvar) = &*pair_clone;
/// let mut ready = mutex.lock_sync();
/// *ready = true;
/// drop(ready);
/// condvar.notify_one();
/// });
///
/// let (mutex, condvar) = &*pair;
/// let mut ready = mutex.lock_sync();
/// // Wait until ready becomes true
/// ready = condvar.wait_spin_while(ready, |r| !*r);
/// assert!(*ready);
/// ```
pub fn wait_spin_while<'a, T, F>(
&self,
mut guard: Guard<'a, T>,
mut condition: F,
) -> Guard<'a, T>
where
F: FnMut(&mut T) -> bool,
{
while condition(&mut guard) {
guard = self.wait_spin(guard);
}
guard
}
/// Waits by spinning with a deadline for notification.
///
/// This method will atomically unlock the mutex specified by the guard and
/// spin in a tight loop while waiting for notification or the deadline. When a notification is received
/// or the timeout expires, the mutex will be re-acquired before returning.
///
/// # Examples
///
/// ```
/// # // std::thread::spawn panics on wasm32
/// # if cfg!(target_arch = "wasm32") { return; }
/// use wasm_safe_mutex::{Mutex, condvar::Condvar};
/// use std::sync::Arc;
/// # #[cfg(target_arch = "wasm32")]
/// use web_time::{Duration, Instant};
/// # #[cfg(not(target_arch = "wasm32"))]
/// # use std::time::{Duration, Instant};
/// # use std::thread;
///
/// let pair = Arc::new((Mutex::new(false), Condvar::new()));
/// let pair_clone = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (mutex, condvar) = &*pair_clone;
/// let mut ready = mutex.lock_sync();
/// *ready = true;
/// drop(ready);
/// condvar.notify_one();
/// });
///
/// let (mutex, condvar) = &*pair;
/// let mut ready = mutex.lock_sync();
/// let deadline = Instant::now() + Duration::from_secs(1);
/// while !*ready {
/// let result;
/// (ready, result) = condvar.wait_spin_timeout(ready, deadline);
/// if result.timed_out() {
/// break;
/// }
/// }
/// ```
pub fn wait_spin_timeout<'a, T>(
&self,
guard: Guard<'a, T>,
deadline: Instant,
) -> (Guard<'a, T>, WaitTimeoutResult) {
let wake = Arc::new(AtomicBool::new(false));
let mutex = guard.mutex;
//insert into wait queue
self.waiting_spin_threads.with_mut(|e| e.push(wake.clone()));
// Release the mutex
drop(guard);
loop {
if wake.load(Ordering::Acquire) {
// Re-acquire the mutex before returning
return (mutex.lock_sync(), WaitTimeoutResult(false));
}
if Instant::now() >= deadline {
// We timed out. We need to remove ourselves from the wait list.
// It's possible we were notified just now, so we check one last time after locking.
let notified = self.waiting_spin_threads.with_mut(|threads| {
// Find our wake arc and remove it
if let Some(pos) = threads.iter().position(|x| Arc::ptr_eq(x, &wake)) {
threads.remove(pos);
false // We removed ourselves, so we were NOT notified by someone else popping us
} else {
true // We were not in the list, so we MUST have been notified/popped
}
});
if notified {
// We were notified, so we shouldn't return timeout.
// We still need to wait for the wake flag to be set to true by the notifier
// effectively behaving as a normal wait_spin completion.
while !wake.load(Ordering::Acquire) {
std::hint::spin_loop();
}
return (mutex.lock_sync(), WaitTimeoutResult(false));
} else {
return (mutex.lock_sync(), WaitTimeoutResult(true));
}
}
std::hint::spin_loop();
}
}
/// Waits by spinning while the predicate remains `true` with a deadline.
///
/// This method will atomically unlock the mutex specified by the guard and
/// spin in a tight loop as long as the `condition` closure returns `true`.
///
/// # Platform Behavior
///
/// - **All Platforms**: Uses a busy loop (spinning) to wait. This consumes CPU
/// cycles but works in all environments, including WASM main thread.
///
/// # Predicate
///
/// The `condition` closure is called:
/// 1. Before waiting (if it returns `false`, the method returns immediately)
/// 2. After each notification (to check if we should keep waiting)
/// 3. After spurious wakeups (to ensure we don't return prematurely)
///
/// # Spurious Wakeups
///
/// This method automatically handles spurious wakeups by re-checking the condition.
/// You do not need to loop around this call.
///
/// # Examples
///
/// ```
/// # // std::thread::spawn panics on wasm32
/// # if cfg!(target_arch = "wasm32") { return; }
/// use wasm_safe_mutex::{Mutex, condvar::Condvar};
/// use std::sync::Arc;
/// # #[cfg(target_arch = "wasm32")]
/// use web_time::{Duration, Instant};
/// # #[cfg(not(target_arch = "wasm32"))]
/// # use std::time::{Duration, Instant};
/// # use std::thread;
///
/// let pair = Arc::new((Mutex::new(0), Condvar::new()));
/// let pair_clone = Arc::clone(&pair);
///
/// thread::spawn(move || {
/// let (mutex, condvar) = &*pair_clone;
/// let mut value = mutex.lock_sync();
/// *value = 10;
/// drop(value);
/// condvar.notify_one();
/// });
///
/// let (mutex, condvar) = &*pair;
/// let mut guard = mutex.lock_sync();
/// let deadline = Instant::now() + Duration::from_secs(1);
/// let (guard, result) = condvar.wait_spin_timeout_while(guard, deadline, |v| *v < 10);
/// if !result.timed_out() {
/// assert_eq!(*guard, 10);
/// }
/// ```
pub fn wait_spin_timeout_while<'a, T, F>(
&self,
mut guard: Guard<'a, T>,
deadline: Instant,
mut condition: F,
) -> (Guard<'a, T>, WaitTimeoutResult)
where
F: FnMut(&mut T) -> bool,
{
while condition(&mut guard) {
let result;
(guard, result) = self.wait_spin_timeout(guard, deadline);
if result.timed_out() {
return (guard, result);
}
}
(guard, WaitTimeoutResult(false))
}
}