add contention test

ci/script.sh

@@ -11,8 +11,9 @@ main() {
             cargo test --target $TARGET
             cargo test --target $TARGET --release
 
-            export TSAN_OPTIONS="suppressions=$(pwd)/blacklist.txt"
             export RUSTFLAGS="-Z sanitizer=thread"
+            export RUST_TEST_THREADS=1
+            export TSAN_OPTIONS="suppressions=$(pwd)/blacklist.txt"
 
             cargo test --test tsan --target $TARGET
             cargo test --test tsan --target $TARGET --release

src/ring_buffer/mod.rs

@@ -129,6 +129,11 @@ where
         }
     }
 
+    /// Returns `true` if the ring buffer has a length of 0
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     /// Iterates from the front of the queue to the back
     pub fn iter(&self) -> Iter<T, A> {
         Iter {

tests/tsan.rs

@@ -73,3 +73,48 @@ fn scoped() {
 
     rb.dequeue().unwrap();
 }
+
+#[test]
+fn contention() {
+    const N: usize = 1024;
+
+    let mut rb: RingBuffer<u8, [u8; N]> = RingBuffer::new();
+
+    {
+        let (mut p, mut c) = rb.split();
+
+        Pool::new(2).scoped(move |scope| {
+            scope.execute(move || {
+                let mut sum: u32 = 0;
+
+                for i in 0..N {
+                    let i = i as u8;
+                    sum = sum.wrapping_add(i as u32);
+                    while let Err(_) = p.enqueue(i) {}
+                }
+
+                println!("producer: {}", sum);
+            });
+
+            scope.execute(move || {
+                let mut sum: u32 = 0;
+
+                for _ in 0..N {
+                    loop {
+                        match c.dequeue() {
+                            Some(v) => {
+                                sum = sum.wrapping_add(v as u32);
+                                break;
+                            }
+                            _ => {}
+                        }
+                    }
+                }
+
+                println!("consumer: {}", sum);
+            });
+        });
+    }
+
+    assert!(rb.is_empty());
+}