path: root/src/tools/miri/tests/pass/concurrency/sync.rs

//@revisions: stack tree
//@[tree]compile-flags: -Zmiri-tree-borrows
// We use `yield` to test specific interleavings, so disable automatic preemption.
//@compile-flags: -Zmiri-disable-isolation -Zmiri-deterministic-concurrency

use std::sync::{Arc, Barrier, Condvar, Mutex, Once, RwLock};
use std::thread;
use std::time::{Duration, Instant};

// We are expecting to sleep for 10ms. How long of a sleep we are accepting?
// Even with 1000ms we still see this test fail on macOS runners.
// On a aarch64-pc-windows-msvc runner, we saw 2.7s!
const MAX_SLEEP_TIME_MS: u64 = 4000;

// Check if Rust barriers are working.

/// This test is taken from the Rust documentation.
fn check_barriers() {
    let mut handles = Vec::with_capacity(10);
    let barrier = Arc::new(Barrier::new(10));
    for _ in 0..10 {
        let c = barrier.clone();
        // The same messages will be printed together.
        // You will NOT see any interleaving.
        handles.push(thread::spawn(move || {
            println!("before wait");
            c.wait();
            println!("after wait");
        }));
    }
    // Wait for other threads to finish.
    for handle in handles {
        handle.join().unwrap();
    }
}

// Check if Rust conditional variables are working.

/// The test taken from the Rust documentation.
fn check_conditional_variables_notify_one() {
    let pair = Arc::new((Mutex::new(false), Condvar::new()));
    let pair2 = pair.clone();

    // Spawn a new thread.
    let t = thread::spawn(move || {
        thread::yield_now();
        let (lock, cvar) = &*pair2;
        let mut started = lock.lock().unwrap();
        *started = true;
        // We notify the condvar that the value has changed.
        cvar.notify_one();
    });

    // Wait for the thread to fully start up.
    let (lock, cvar) = &*pair;
    let mut started = lock.lock().unwrap();
    while !*started {
        started = cvar.wait(started).unwrap();
    }

    t.join().unwrap();
}

/// Test that waiting on a conditional variable with a timeout does not
/// deadlock.
fn check_conditional_variables_timed_wait_timeout() {
    let lock = Mutex::new(());
    let cvar = Condvar::new();
    let guard = lock.lock().unwrap();
    let now = Instant::now();
    let (_guard, timeout) = cvar.wait_timeout(guard, Duration::from_millis(10)).unwrap();
    assert!(timeout.timed_out());
    let elapsed_time = now.elapsed().as_millis();
    assert!(10 <= elapsed_time && elapsed_time <= MAX_SLEEP_TIME_MS.into());
}

/// Test that signaling a conditional variable when waiting with a timeout works
/// as expected.
fn check_conditional_variables_timed_wait_notimeout() {
    let pair = Arc::new((Mutex::new(()), Condvar::new()));
    let pair2 = pair.clone();

    let (lock, cvar) = &*pair;
    let guard = lock.lock().unwrap();

    let handle = thread::spawn(move || {
        thread::sleep(Duration::from_millis(1)); // Make sure the other thread is waiting by the time we call `notify`.
        let (_lock, cvar) = &*pair2;
        cvar.notify_one();
    });

    let (_guard, timeout) =
        cvar.wait_timeout(guard, Duration::from_millis(MAX_SLEEP_TIME_MS)).unwrap();
    assert!(!timeout.timed_out());
    handle.join().unwrap();
}

// Check if locks are working.

fn check_mutex() {
    let data = Arc::new(Mutex::new(0));
    let mut threads = Vec::new();

    for _ in 0..3 {
        let data = Arc::clone(&data);
        let thread = thread::spawn(move || {
            let mut data = data.lock().unwrap();
            thread::yield_now();
            *data += 1;
        });
        threads.push(thread);
    }

    for thread in threads {
        thread.join().unwrap();
    }

    assert!(data.try_lock().is_ok());

    let data = Arc::try_unwrap(data).unwrap().into_inner().unwrap();
    assert_eq!(data, 3);
}

fn check_rwlock_write() {
    let data = Arc::new(RwLock::new(0));
    let mut threads = Vec::new();

    for _ in 0..3 {
        let thread = thread::spawn({
            let data = Arc::clone(&data);
            move || {
                let mut data = data.write().unwrap();
                thread::yield_now();
                *data += 1;
            }
        });
        threads.push(thread);

        let readthread = thread::spawn({
            let data = Arc::clone(&data);
            move || {
                let data = data.read().unwrap();
                thread::yield_now();
                assert!(*data >= 0 && *data <= 3);
            }
        });
        threads.push(readthread);
    }

    for thread in threads {
        thread.join().unwrap();
    }

    assert!(data.try_write().is_ok());

    let data = Arc::try_unwrap(data).unwrap().into_inner().unwrap();
    assert_eq!(data, 3);
}

fn check_rwlock_read_no_deadlock() {
    let l1 = Arc::new(RwLock::new(0));
    let l2 = Arc::new(RwLock::new(0));

    let l1_copy = Arc::clone(&l1);
    let l2_copy = Arc::clone(&l2);
    // acquire l1 and hold it until after the other thread is done
    let _guard1 = l1.read().unwrap();
    let handle = thread::spawn(move || {
        // acquire l2 before the other thread
        let _guard2 = l2_copy.read().unwrap();
        thread::yield_now();
        let _guard1 = l1_copy.read().unwrap();
    });
    thread::yield_now();
    let _guard2 = l2.read().unwrap();
    handle.join().unwrap();
}

// Check if Rust once statics are working.

static mut VAL: usize = 0;
static INIT: Once = Once::new();

fn get_cached_val() -> usize {
    unsafe {
        INIT.call_once(|| {
            VAL = expensive_computation();
        });
        VAL
    }
}

fn expensive_computation() -> usize {
    let mut i = 1;
    let mut c = 1;
    while i < 1000 {
        i *= c;
        c += 1;
    }
    i
}

/// The test taken from the Rust documentation.
fn check_once() {
    let handles: Vec<_> = (0..10)
        .map(|_| {
            thread::spawn(|| {
                thread::yield_now();
                let val = get_cached_val();
                assert_eq!(val, 5040);
            })
        })
        .collect();
    for handle in handles {
        handle.join().unwrap();
    }
}

fn park_timeout() {
    let start = Instant::now();

    thread::park_timeout(Duration::from_millis(10));
    // Normally, waiting in park/park_timeout may spuriously wake up early, but we
    // know Miri's timed synchronization primitives do not do that.
    let elapsed = start.elapsed();
    assert!(
        (10..MAX_SLEEP_TIME_MS.into()).contains(&elapsed.as_millis()),
        "bad sleep time: {elapsed:?}"
    );
}

fn park_unpark() {
    let t1 = thread::current();
    let t2 = thread::spawn(move || {
        thread::park();
        thread::sleep(Duration::from_millis(10));
        t1.unpark();
    });

    let start = Instant::now();

    t2.thread().unpark();
    thread::park();
    // Normally, waiting in park/park_timeout may spuriously wake up early, but we
    // know Miri's timed synchronization primitives do not do that.
    let elapsed = start.elapsed();
    assert!(
        (10..MAX_SLEEP_TIME_MS.into()).contains(&elapsed.as_millis()),
        "bad sleep time: {elapsed:?}"
    );

    t2.join().unwrap();
}

fn main() {
    check_mutex();
    check_rwlock_write();
    check_rwlock_read_no_deadlock();
    check_once();
    park_timeout();
    park_unpark();
    check_barriers();
    check_conditional_variables_notify_one();
    check_conditional_variables_timed_wait_timeout();
    check_conditional_variables_timed_wait_notimeout();
}