switch to PCT shuttle scheduler

Author: ibraheemdev

.github/workflows/test.yml

@@ -59,8 +59,6 @@ jobs:
         run: cargo test --workspace --doc
       - name: Check (without default features)
         run: cargo check --workspace --no-default-features
-      - name: Check (loom)
-        run: RUSTFLAGS="--cfg loom" cargo check --workspace --features loom
 
   miri:
     name: Miri

tests/parallel/main.rs

@@ -31,7 +31,7 @@ pub(crate) mod sync {
 
     pub fn check(f: impl Fn() + Send + Sync + 'static) {
         let _serialize = SERIALIZE.lock();
-        shuttle::check_random(f, 500);
+        shuttle::check_pct(f, 1000, 50);
     }
 }
 

tests/parallel/setup.rs

@@ -1,3 +1,5 @@
+#![allow(dead_code)]
+
 use salsa::{Database, Storage};
 
 use super::signal::Signal;

tests/parallel/signal.rs

@@ -1,3 +1,5 @@
+#![allow(unused)]
+
 use super::sync::{Condvar, Mutex};
 
 #[derive(Default)]
@@ -8,28 +10,36 @@ pub(crate) struct Signal {
 
 impl Signal {
     pub(crate) fn signal(&self, stage: usize) {
-        // 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().unwrap();
-            if stage > *v {
-                *v = stage;
-                self.cond_var.notify_all();
+        // When running with shuttle we want to explore all possible
+        // executions, so we avoid signals entirely.
+        #[cfg(not(feature = "shuttle"))]
+        {
+            // 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().unwrap();
+                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) {
-        // As above, avoid lock if clearly a no-op.
-        if stage > 0 {
-            let mut v = self.value.lock().unwrap();
-            while *v < stage {
-                v = self.cond_var.wait(v).unwrap();
+        #[cfg(not(feature = "shuttle"))]
+        {
+            // As above, avoid lock if clearly a no-op.
+            if stage > 0 {
+                let mut v = self.value.lock().unwrap();
+                while *v < stage {
+                    v = self.cond_var.wait(v).unwrap();
+                }
             }
         }
     }