Merge #874

874: Use get_mut instead of atomic load in Drop impls r=taiki-e a=taiki-e

Similar to #811, but for deque and queue.

Co-authored-by: Taiki Endo <te316e89@gmail.com>

crossbeam-deque/src/deque.rs

@@ -116,8 +116,8 @@ struct Inner<T> {
 impl<T> Drop for Inner<T> {
     fn drop(&mut self) {
         // Load the back index, front index, and buffer.
-        let b = self.back.load(Ordering::Relaxed);
-        let f = self.front.load(Ordering::Relaxed);
+        let b = *self.back.get_mut();
+        let f = *self.front.get_mut();
 
         unsafe {
             let buffer = self.buffer.load(Ordering::Relaxed, epoch::unprotected());
@@ -1816,9 +1816,9 @@ impl<T> Injector<T> {
 
 impl<T> Drop for Injector<T> {
     fn drop(&mut self) {
-        let mut head = self.head.index.load(Ordering::Relaxed);
-        let mut tail = self.tail.index.load(Ordering::Relaxed);
-        let mut block = self.head.block.load(Ordering::Relaxed);
+        let mut head = *self.head.index.get_mut();
+        let mut tail = *self.tail.index.get_mut();
+        let mut block = *self.head.block.get_mut();
 
         // Erase the lower bits.
         head &= !((1 << SHIFT) - 1);
@@ -1836,7 +1836,7 @@ impl<T> Drop for Injector<T> {
                     p.as_mut_ptr().drop_in_place();
                 } else {
                     // Deallocate the block and move to the next one.
-                    let next = (*block).next.load(Ordering::Relaxed);
+                    let next = *(*block).next.get_mut();
                     drop(Box::from_raw(block));
                     block = next;
                 }

crossbeam-queue/src/array_queue.rs

@@ -444,10 +444,24 @@ impl<T> ArrayQueue<T> {
 impl<T> Drop for ArrayQueue<T> {
     fn drop(&mut self) {
         // Get the index of the head.
-        let hix = self.head.load(Ordering::Relaxed) & (self.one_lap - 1);
+        let head = *self.head.get_mut();
+        let tail = *self.tail.get_mut();
+
+        let hix = head & (self.one_lap - 1);
+        let tix = tail & (self.one_lap - 1);
+
+        let len = if hix < tix {
+            tix - hix
+        } else if hix > tix {
+            self.cap - hix + tix
+        } else if tail == head {
+            0
+        } else {
+            self.cap
+        };
 
         // Loop over all slots that hold a message and drop them.
-        for i in 0..self.len() {
+        for i in 0..len {
             // Compute the index of the next slot holding a message.
             let index = if hix + i < self.cap {
                 hix + i

crossbeam-queue/src/seg_queue.rs

@@ -437,9 +437,9 @@ impl<T> SegQueue<T> {
 
 impl<T> Drop for SegQueue<T> {
     fn drop(&mut self) {
-        let mut head = self.head.index.load(Ordering::Relaxed);
-        let mut tail = self.tail.index.load(Ordering::Relaxed);
-        let mut block = self.head.block.load(Ordering::Relaxed);
+        let mut head = *self.head.index.get_mut();
+        let mut tail = *self.tail.index.get_mut();
+        let mut block = *self.head.block.get_mut();
 
         // Erase the lower bits.
         head &= !((1 << SHIFT) - 1);
@@ -457,7 +457,7 @@ impl<T> Drop for SegQueue<T> {
                     p.as_mut_ptr().drop_in_place();
                 } else {
                     // Deallocate the block and move to the next one.
-                    let next = (*block).next.load(Ordering::Relaxed);
+                    let next = *(*block).next.get_mut();
                     drop(Box::from_raw(block));
                     block = next;
                 }