From: Ivan Maidanski <ivmai@mail.ru>
Date: Mon, 30 Oct 2017 22:09:56 +0000 (+0300)
Subject: Workaround TSan false positive in invoke_finalizers
X-Git-Tag: v8.0.0~529
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=57f22ff97d7961784ad7e93578558990ddd74e2e;p=gc

Workaround TSan false positive in invoke_finalizers

* finalize.c [THREADS && !THREAD_SANITIZER] (GC_invoke_finalizers): Do
not compare bytes_freed_before to GC_bytes_freed without the lock; add
comment.
* include/private/gc_priv.h (_GC_arrays._finalizer_bytes_freed): Replace
"mem." to "memory" in a comment.
---

diff --git a/finalize.c b/finalize.c
index 0c39b54d..aaed8d4e 100644
--- a/finalize.c
+++ b/finalize.c
@@ -1224,7 +1224,15 @@ GC_API int GC_CALL GC_invoke_finalizers(void)
         /* finalizable.  Otherwise it should not matter.        */
     }
     /* bytes_freed_before is initialized whenever count != 0 */
-    if (count != 0 && bytes_freed_before != GC_bytes_freed) {
+    if (count != 0
+#         if defined(THREADS) && !defined(THREAD_SANITIZER)
+            /* A quick check whether some memory was freed.     */
+            /* The race with GC_free() is safe to be ignored    */
+            /* because we only need to know if the current      */
+            /* thread has deallocated something.                */
+            && bytes_freed_before != GC_bytes_freed
+#         endif
+       ) {
         LOCK();
         GC_finalizer_bytes_freed += (GC_bytes_freed - bytes_freed_before);
         UNLOCK();
diff --git a/include/private/gc_priv.h b/include/private/gc_priv.h
index 7fc977d7..e10bcfde 100644
--- a/include/private/gc_priv.h
+++ b/include/private/gc_priv.h
@@ -1224,7 +1224,7 @@ struct _GC_arrays {
         /* since last collection.                               */
   word _finalizer_bytes_freed;
         /* Bytes of memory explicitly deallocated while         */
-        /* finalizers were running.  Used to approximate mem.   */
+        /* finalizers were running.  Used to approximate memory */
         /* explicitly deallocated by finalizers.                */
   ptr_t _scratch_end_ptr;
   ptr_t _scratch_last_end_ptr;