Rollup merge of rust-lang#71737 - RalfJung:miri-test-threads, r=shepm…

…aster

Miri: run liballoc tests with threads

Miri now supports threads, so we can run these tests. :)

src/liballoc/alloc/tests.rs

@@ -23,7 +23,7 @@ fn allocate_zeroed() {
 }
 
 #[bench]
-#[cfg_attr(miri, ignore)] // Miri does not support benchmarks
+#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks
 fn alloc_owned_small(b: &mut Bencher) {
     b.iter(|| {
         let _: Box<_> = box 10;

src/liballoc/collections/linked_list/tests.rs

@@ -182,7 +182,6 @@ fn test_insert_prev() {
 
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)]
-#[cfg_attr(miri, ignore)] // Miri does not support threads
 fn test_send() {
     let n = list_from(&[1, 2, 3]);
     thread::spawn(move || {

src/liballoc/collections/vec_deque/tests.rs

@@ -3,7 +3,7 @@ use super::*;
 use test;
 
 #[bench]
-#[cfg_attr(miri, ignore)] // Miri does not support benchmarks
+#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks
 fn bench_push_back_100(b: &mut test::Bencher) {
     let mut deq = VecDeque::with_capacity(101);
     b.iter(|| {
@@ -16,7 +16,7 @@ fn bench_push_back_100(b: &mut test::Bencher) {
 }
 
 #[bench]
-#[cfg_attr(miri, ignore)] // Miri does not support benchmarks
+#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks
 fn bench_push_front_100(b: &mut test::Bencher) {
     let mut deq = VecDeque::with_capacity(101);
     b.iter(|| {
@@ -29,7 +29,7 @@ fn bench_push_front_100(b: &mut test::Bencher) {
 }
 
 #[bench]
-#[cfg_attr(miri, ignore)] // Miri does not support benchmarks
+#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks
 fn bench_pop_back_100(b: &mut test::Bencher) {
     let mut deq = VecDeque::<i32>::with_capacity(101);
 
@@ -43,7 +43,7 @@ fn bench_pop_back_100(b: &mut test::Bencher) {
 }
 
 #[bench]
-#[cfg_attr(miri, ignore)] // Miri does not support benchmarks
+#[cfg_attr(miri, ignore)] // isolated Miri does not support benchmarks
 fn bench_pop_front_100(b: &mut test::Bencher) {
     let mut deq = VecDeque::<i32>::with_capacity(101);
 

src/liballoc/sync/tests.rs

@@ -32,7 +32,6 @@ impl Drop for Canary {
 
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)]
-#[cfg_attr(miri, ignore)] // Miri does not support threads
 fn manually_share_arc() {
     let v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
     let arc_v = Arc::new(v);
@@ -337,12 +336,13 @@ fn test_ptr_eq() {
 
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)]
-#[cfg_attr(miri, ignore)] // Miri does not support threads
 fn test_weak_count_locked() {
     let mut a = Arc::new(atomic::AtomicBool::new(false));
     let a2 = a.clone();
     let t = thread::spawn(move || {
-        for _i in 0..1000000 {
+        // Miri is too slow
+        let count = if cfg!(miri) { 1000 } else { 1000000 };
+        for _i in 0..count {
             Arc::get_mut(&mut a);
         }
         a.store(true, SeqCst);
@@ -351,6 +351,8 @@ fn test_weak_count_locked() {
     while !a2.load(SeqCst) {
         let n = Arc::weak_count(&a2);
         assert!(n < 2, "bad weak count: {}", n);
+        #[cfg(miri)] // Miri's scheduler does not guarantee liveness, and thus needs this hint.
+        atomic::spin_loop_hint();
     }
     t.join().unwrap();
 }