rust/tests/pass/weak_memory/weak.rs

107 lines
2.6 KiB
Rust
Raw Normal View History

2022-07-08 11:08:32 -05:00
//@ignore-windows: Concurrency on Windows is not supported yet.
//@compile-flags: -Zmiri-ignore-leaks -Zmiri-preemption-rate=0
// Tests showing weak memory behaviours are exhibited. All tests
// return true when the desired behaviour is seen.
// This is scheduler and pseudo-RNG dependent, so each test is
// run multiple times until one try returns true.
// Spurious failure is possible, if you are really unlucky with
// the RNG and always read the latest value from the store buffer.
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering::*;
use std::thread::spawn;
#[derive(Copy, Clone)]
struct EvilSend<T>(pub T);
unsafe impl<T> Send for EvilSend<T> {}
unsafe impl<T> Sync for EvilSend<T> {}
// We can't create static items because we need to run each test
// multiple times
fn static_atomic(val: usize) -> &'static AtomicUsize {
let ret = Box::leak(Box::new(AtomicUsize::new(val)));
ret
}
// Spins until it reads the given value
fn reads_value(loc: &AtomicUsize, val: usize) -> usize {
while loc.load(Relaxed) != val {
std::hint::spin_loop();
}
val
}
fn relaxed() -> bool {
let x = static_atomic(0);
let j1 = spawn(move || {
x.store(1, Relaxed);
x.store(2, Relaxed);
});
let j2 = spawn(move || x.load(Relaxed));
j1.join().unwrap();
let r2 = j2.join().unwrap();
r2 == 1
}
// https://www.doc.ic.ac.uk/~afd/homepages/papers/pdfs/2017/POPL.pdf Figure 8
fn seq_cst() -> bool {
let x = static_atomic(0);
let j1 = spawn(move || {
x.store(1, Relaxed);
});
let j2 = spawn(move || {
x.store(2, SeqCst);
x.store(3, SeqCst);
});
let j3 = spawn(move || x.load(SeqCst));
j1.join().unwrap();
j2.join().unwrap();
let r3 = j3.join().unwrap();
r3 == 1
}
fn initialization_write() -> bool {
let x = static_atomic(11);
2022-07-14 07:13:24 -05:00
assert_eq!(x.load(Relaxed), 11); // work around https://github.com/rust-lang/miri/issues/2164
let wait = static_atomic(0);
let j1 = spawn(move || {
x.store(22, Relaxed);
// Relaxed is intentional. We want to test if the thread 2 reads the initialisation write
// after a relaxed write
wait.store(1, Relaxed);
});
let j2 = spawn(move || {
reads_value(wait, 1);
x.load(Relaxed)
});
j1.join().unwrap();
let r2 = j2.join().unwrap();
r2 == 11
}
2022-07-14 07:13:24 -05:00
/// Asserts that the function returns true at least once in 100 runs
fn assert_once(f: fn() -> bool) {
assert!(std::iter::repeat_with(|| f()).take(100).any(|x| x));
}
pub fn main() {
2022-07-14 07:13:24 -05:00
assert_once(relaxed);
assert_once(seq_cst);
assert_once(initialization_write);
}