Fix miri test

Author: taiki-e

crossbeam-channel/tests/golang.rs

@@ -1580,9 +1580,7 @@ mod race_chan_test {
 }
 
 // https://github.com/golang/go/blob/master/test/ken/chan.go
-#[cfg(not(miri))] // Miri is too slow
 mod chan {
-
     use super::*;
 
     const MESSAGES_PER_CHANEL: u32 = 76;
@@ -2052,6 +2050,7 @@ mod chan {
     }
 
     #[test]
+    #[cfg_attr(miri, ignore)] // Miri is too slow
     fn main() {
         let mut ctx = Context {
             nproc: Arc::new(Mutex::new(0)),

crossbeam-channel/tests/list.rs

@@ -67,6 +67,7 @@ fn len_empty_full() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore)] // this test makes timing assumptions, but Miri is so slow it violates them
 fn try_recv() {
     let (s, r) = unbounded();
 

crossbeam-channel/tests/select.rs

@@ -408,7 +408,6 @@ fn both_ready() {
     .unwrap();
 }
 
-#[cfg_attr(miri, ignore)] // Miri is too slow
 #[test]
 fn loop_try() {
     const RUNS: usize = 20;

crossbeam-channel/tests/select_macro.rs

@@ -284,7 +284,6 @@ fn both_ready() {
     .unwrap();
 }
 
-#[cfg_attr(miri, ignore)] // Miri is too slow
 #[test]
 fn loop_try() {
     const RUNS: usize = 20;

crossbeam-channel/tests/zero.rs

@@ -328,9 +328,11 @@ fn stress_oneshot() {
     }
 }
 
-#[cfg_attr(miri, ignore)] // Miri is too slow
 #[test]
 fn stress_iter() {
+    #[cfg(miri)]
+    const COUNT: usize = 50;
+    #[cfg(not(miri))]
     const COUNT: usize = 1000;
 
     let (request_s, request_r) = bounded(0);
@@ -483,10 +485,9 @@ fn fairness() {
 }
 
 #[test]
-#[cfg_attr(miri, ignore)] // Miri is too slow
 fn fairness_duplicates() {
     #[cfg(miri)]
-    const COUNT: usize = 50;
+    const COUNT: usize = 100;
     #[cfg(not(miri))]
     const COUNT: usize = 10_000;
 

crossbeam-epoch/src/collector.rs

@@ -402,10 +402,10 @@ mod tests {
                 v.push(i as i32);
             }
 
-            let ptr = v.as_mut_ptr() as usize;
+            let ptr = v.as_mut_ptr();
             let len = v.len();
             guard.defer_unchecked(move || {
-                drop(Vec::from_raw_parts(ptr as *const i32 as *mut i32, len, len));
+                drop(Vec::from_raw_parts(ptr, len, len));
                 DESTROYS.fetch_add(len, Ordering::Relaxed);
             });
             guard.flush();

crossbeam-queue/tests/array_queue.rs

@@ -193,9 +193,11 @@ fn spsc_ring_buffer() {
     }
 }
 
-#[cfg_attr(miri, ignore)] // Miri is too slow
 #[test]
 fn mpmc() {
+    #[cfg(miri)]
+    const COUNT: usize = 50;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
 
@@ -230,9 +232,11 @@ fn mpmc() {
     }
 }
 
-#[cfg_attr(miri, ignore)] // Miri is too slow
 #[test]
 fn mpmc_ring_buffer() {
+    #[cfg(miri)]
+    const COUNT: usize = 50;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
 

crossbeam-queue/tests/seg_queue.rs

@@ -82,9 +82,11 @@ fn spsc() {
     .unwrap();
 }
 
-#[cfg_attr(miri, ignore)] // Miri is too slow
 #[test]
 fn mpmc() {
+    #[cfg(miri)]
+    const COUNT: usize = 50;
+    #[cfg(not(miri))]
     const COUNT: usize = 25_000;
     const THREADS: usize = 4;
 

crossbeam-utils/src/atomic/atomic_cell.rs

@@ -1009,10 +1009,11 @@ where
                 // discard the data when a data race is detected. The proper solution would be to
                 // do atomic reads and atomic writes, but we can't atomically read and write all
                 // kinds of data since `AtomicU8` is not available on stable Rust yet.
-                let val = ptr::read_volatile(src);
+                // Load as `MaybeUninit` because we may load a value that is not valid as `T`.
+                let val = ptr::read_volatile(src as *mut MaybeUninit<T>);
 
                 if lock.validate_read(stamp) {
-                    return val;
+                    return val.assume_init();
                 }
             }