From c66d02e3ba0d5ace4e42bab88e4df246f03b91d5 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Fri, 1 May 2020 11:16:38 +0200
Subject: [PATCH 1/2] liballoc tests: Miri supports threads now

---
 src/liballoc/alloc/tests.rs                   | 2 +-
 src/liballoc/collections/linked_list/tests.rs | 1 -
 src/liballoc/collections/vec_deque/tests.rs   | 8 ++++----
 src/liballoc/sync/tests.rs                    | 2 --
 4 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/src/liballoc/alloc/tests.rs b/src/liballoc/alloc/tests.rs
index 1ad40eca93b69..1c003983df989 100644
--- a/src/liballoc/alloc/tests.rs
+++ b/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;
diff --git a/src/liballoc/collections/linked_list/tests.rs b/src/liballoc/collections/linked_list/tests.rs
index 085f734ed916a..b8c93a28bba81 100644
--- a/src/liballoc/collections/linked_list/tests.rs
+++ b/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 || {
diff --git a/src/liballoc/collections/vec_deque/tests.rs b/src/liballoc/collections/vec_deque/tests.rs
index 0a3f33003233f..fc2ec7908e823 100644
--- a/src/liballoc/collections/vec_deque/tests.rs
+++ b/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);
 
diff --git a/src/liballoc/sync/tests.rs b/src/liballoc/sync/tests.rs
index edc2820ee22f1..4a5cc9aa5910f 100644
--- a/src/liballoc/sync/tests.rs
+++ b/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);
@@ -337,7 +336,6 @@ 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();

From 7bea58eeac3a5a5280810623f06eadb3a8b891a3 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Sun, 3 May 2020 12:34:53 +0200
Subject: [PATCH 2/2] fix test_weak_count_locked for Miri

---
 src/liballoc/sync/tests.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/liballoc/sync/tests.rs b/src/liballoc/sync/tests.rs
index 4a5cc9aa5910f..a2bb651e2b778 100644
--- a/src/liballoc/sync/tests.rs
+++ b/src/liballoc/sync/tests.rs
@@ -340,7 +340,9 @@ 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);
@@ -349,6 +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();
 }