vendor/salsa/tests/parallel/signal.rs

   1 use parking_lot::{Condvar, Mutex};
   2
   3 #[derive(Default)]
   4 pub(crate) struct Signal {
   5     value: Mutex<usize>,
   6     cond_var: Condvar,
   7 }
   8
   9 impl Signal {
  10     pub(crate) fn signal(&self, stage: usize) {
  11         log::debug!("signal({})", stage);
  12
  13         // This check avoids acquiring the lock for things that will
  14         // clearly be a no-op. Not *necessary* but helps to ensure we
  15         // are more likely to encounter weird race conditions;
  16         // otherwise calls to `sum` will tend to be unnecessarily
  17         // synchronous.
  18         if stage > 0 {
  19             let mut v = self.value.lock();
  20             if stage > *v {
  21                 *v = stage;
  22                 self.cond_var.notify_all();
  23             }
  24         }
  25     }
  26
  27     /// Waits until the given condition is true; the fn is invoked
  28     /// with the current stage.
  29     pub(crate) fn wait_for(&self, stage: usize) {
  30         log::debug!("wait_for({})", stage);
  31
  32         // As above, avoid lock if clearly a no-op.
  33         if stage > 0 {
  34             let mut v = self.value.lock();
  35             while *v < stage {
  36                 self.cond_var.wait(&mut v);
  37             }
  38         }
  39     }
  40 }