sync: track loom changes (#1405)

tokio-sync/src/loom.rs

@@ -31,6 +31,8 @@ pub(crate) mod sync {
     }
 }
 
-pub(crate) fn yield_now() {
-    ::std::sync::atomic::spin_loop_hint();
+pub(crate) mod thread {
+    pub(crate) fn yield_now() {
+        ::std::sync::atomic::spin_loop_hint();
+    }
 }

tokio-sync/src/mpsc/block.rs

@@ -1,7 +1,7 @@
 use crate::loom::{
-    self,
     sync::atomic::{AtomicPtr, AtomicUsize},
     sync::CausalCell,
+    thread,
 };
 use std::mem::{self, ManuallyDrop};
 use std::ops;
@@ -344,7 +344,7 @@ impl<T> Block<T> {
             };
 
             // When running outside of loom, this calls `spin_loop_hint`.
-            loom::yield_now();
+            thread::yield_now();
         }
     }
 }

tokio-sync/src/mpsc/list.rs

@@ -2,8 +2,8 @@
 
 use super::block::{self, Block};
 use crate::loom::{
-    self,
     sync::atomic::{AtomicPtr, AtomicUsize},
+    thread,
 };
 use std::fmt;
 use std::ptr::NonNull;
@@ -163,7 +163,7 @@ impl<T> Tx<T> {
 
             block_ptr = next_block.as_ptr();
 
-            loom::yield_now();
+            thread::yield_now();
         }
     }
 
@@ -270,7 +270,7 @@ impl<T> Rx<T> {
 
             self.head = next_block;
 
-            loom::yield_now();
+            thread::yield_now();
         }
     }
 
@@ -308,7 +308,7 @@ impl<T> Rx<T> {
                 tx.reclaim_block(block);
             }
 
-            loom::yield_now();
+            thread::yield_now();
         }
     }
 

tokio-sync/src/semaphore.rs

@@ -14,7 +14,7 @@ use crate::loom::{
         atomic::{AtomicPtr, AtomicUsize},
         CausalCell,
     },
-    yield_now,
+    thread,
 };
 
 use std::fmt;
@@ -432,7 +432,7 @@ impl Semaphore {
                                 if curr.has_waiter(&self.stub) {
                                     // Inconsistent
                                     debug!(" + pop; inconsistent 1");
-                                    yield_now();
+                                    thread::yield_now();
                                     continue 'outer;
                                 }
 
@@ -479,7 +479,7 @@ impl Semaphore {
                 if tail != head {
                     // Inconsistent
                     debug!(" + pop; inconsistent 2");
-                    yield_now();
+                    thread::yield_now();
                     continue 'outer;
                 }
 
@@ -495,7 +495,7 @@ impl Semaphore {
 
                 // Inconsistent state, loop
                 debug!(" + pop; inconsistent 3");
-                yield_now();
+                thread::yield_now();
             }
         }
     }

tokio-sync/tests/fuzz_list.rs

@@ -63,7 +63,7 @@ fn smoke() {
                 }
                 None => {
                     debug!(" + pop() -> None");
-                    loom::yield_now();
+                    thread::yield_now();
                 }
             }
         }