From: Ivan Maidanski <ivmai@mail.ru>
Date: Wed, 7 Mar 2018 17:40:05 +0000 (+0300)
Subject: Avoid potential race when storing oh_back_ptr during parallel marking
X-Git-Tag: v8.0.0~294
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=701858e81bff8032262f56b753c7f90facd2ee27;p=gc

Avoid potential race when storing oh_back_ptr during parallel marking

* dbg_mlc.c [KEEP_BACK_PTRS && PARALLEL_MARK] (GC_store_back_pointer):
Store source to dest->oh_back_ptr atomically (unordered atomic store
is sufficient here).
---

diff --git a/dbg_mlc.c b/dbg_mlc.c
index 492a3d4c..610728da 100644
--- a/dbg_mlc.c
+++ b/dbg_mlc.c
@@ -90,7 +90,12 @@
   GC_INNER void GC_store_back_pointer(ptr_t source, ptr_t dest)
   {
     if (GC_HAS_DEBUG_INFO(dest)) {
-      ((oh *)dest) -> oh_back_ptr = HIDE_BACK_PTR(source);
+#     ifdef PARALLEL_MARK
+        AO_store((volatile AO_t *)&((oh *)dest)->oh_back_ptr,
+                 (AO_t)HIDE_BACK_PTR(source));
+#     else
+        ((oh *)dest) -> oh_back_ptr = HIDE_BACK_PTR(source);
+#     endif
     }
   }