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use parking_lot::{Condvar, Mutex};
#[derive(Default)]
pub(crate) struct Signal {
value: Mutex<usize>,
cond_var: Condvar,
}
impl Signal {
pub(crate) fn signal(&self, stage: usize) {
tracing::debug!("signal({})", stage);
// This check avoids acquiring the lock for things that will
// clearly be a no-op. Not *necessary* but helps to ensure we
// are more likely to encounter weird race conditions;
// otherwise calls to `sum` will tend to be unnecessarily
// synchronous.
if stage > 0 {
let mut v = self.value.lock();
if stage > *v {
*v = stage;
self.cond_var.notify_all();
}
}
}
/// Waits until the given condition is true; the fn is invoked
/// with the current stage.
pub(crate) fn wait_for(&self, stage: usize) {
tracing::debug!("wait_for({})", stage);
// As above, avoid lock if clearly a no-op.
if stage > 0 {
let mut v = self.value.lock();
while *v < stage {
self.cond_var.wait(&mut v);
}
}
}
}
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