RFR: Incorrect conditional matrix cleanup in SHMatrix::clean_batched

[Aleksey Shipilev]

On 05/12/2017 04:43 PM, Aleksey Shipilev wrote:
> Hi,
> 
> Zhengyu found this embarrassing bug introduced by me:
> 
> diff -r e0ac01d9dae2 src/share/vm/gc/shenandoah/shenandoahConnectionMatrix.cpp
> --- a/src/share/vm/gc/shenandoah/shenandoahConnectionMatrix.cpp	Fri May 12
> 13:37:36 2017 +0200
> +++ b/src/share/vm/gc/shenandoah/shenandoahConnectionMatrix.cpp	Fri May 12
> 16:30:50 2017 +0200
> @@ -117,7 +117,7 @@
>          size_t start = r * stride;
>          for (size_t i = 0; i < count; i++) {
>            size_t t = start + idxs[i];
> -          if (matrix[t] == 0) {
> +          if (matrix[t] != 0) {
>              matrix[t] = 0;
>            }
>          }
> 

Actually, should assert too:

$ hg diff
diff -r e0ac01d9dae2 src/share/vm/gc/shenandoah/shenandoahConnectionMatrix.cpp
--- a/src/share/vm/gc/shenandoah/shenandoahConnectionMatrix.cpp	Fri May 12
13:37:36 2017 +0200
+++ b/src/share/vm/gc/shenandoah/shenandoahConnectionMatrix.cpp	Fri May 12
16:48:22 2017 +0200
@@ -117,7 +117,7 @@
         size_t start = r * stride;
         for (size_t i = 0; i < count; i++) {
           size_t t = start + idxs[i];
-          if (matrix[t] == 0) {
+          if (matrix[t] != 0) {
             matrix[t] = 0;
           }
         }
@@ -152,4 +152,13 @@

   ShenandoahMatrixCleanupTask cl(_matrix, _stride, idxs, count);
   ShenandoahHeap::heap()->workers()->run_task(&cl);
+
+#ifdef ASSERT
+  for (size_t i = 0; i < count; i++) {
+    for (size_t c = 0; c < _stride; c++) {
+      assert (!is_connected(idxs[i], c), "should not be connected");
+      assert (!is_connected(c, idxs[i]), "should not be connected");
+    }
+  }
+#endif
 }


-Aleksey