usertest: add test_rust_mutex

Add a function to stress-test the kernels futex implementation.

usertest/src/main.rs

@@ -1,4 +1,7 @@
-use std::thread;
+use std::{
+    sync::{Arc, Barrier, Mutex},
+    thread,
+};
 
 fn test_sync() {
     print!("Testing sync syscall ...");
@@ -252,6 +255,42 @@ fn test_rust_thread() {
     println!(" OK");
 }
 
+fn test_rust_mutex() {
+    const THREADS: usize = 32;
+    const ITERS: usize = 1_000;
+
+    print!("Testing rust mutex ...");
+
+    let mtx = Arc::new(Mutex::new(0usize));
+    let barrier = Arc::new(Barrier::new(THREADS));
+
+    let mut handles = Vec::with_capacity(THREADS);
+
+    for _ in 0..THREADS {
+        let mtx = Arc::clone(&mtx);
+        let barrier = Arc::clone(&barrier);
+
+        handles.push(thread::spawn(move || {
+            barrier.wait();
+
+            for _ in 0..ITERS {
+                let mut guard = mtx.lock().unwrap();
+                *guard += 1;
+            }
+        }));
+    }
+
+    for h in handles {
+        h.join().unwrap();
+    }
+
+    let final_val = *mtx.lock().unwrap();
+
+    assert_eq!(final_val, THREADS * ITERS);
+
+    println!(" OK");
+}
+
 fn run_test(test_fn: fn()) {
     // Fork a new process to run the test
     unsafe {
@@ -289,6 +328,7 @@ fn main() {
     run_test(test_rust_file);
     run_test(test_rust_dir);
     run_test(test_rust_thread);
+    run_test(test_rust_mutex);
     let end = std::time::Instant::now();
     println!("All tests passed in {} ms", (end - start).as_millis());
 }