From: Ivan Maidanski <ivmai@mail.ru>
Date: Thu, 14 Dec 2017 07:24:34 +0000 (+0300)
Subject: Workaround TSan false positive in remove_all_threads_but_me
X-Git-Tag: v8.0.0~448
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a239976a7fe8e98f8e6d9afc2bb812cee720a445;p=gc

Workaround TSan false positive in remove_all_threads_but_me

* pthread_support.c [CAN_HANDLE_FORK] (store_to_threads_table): New
static function (defined with GC_ATTR_NO_SANITIZE_THREAD attribute
if CAN_CALL_ATFORK); add comment.
* pthread_support.c [CAN_CALL_ATFORK] (GC_remove_all_threads_but_me):
Call store_to_threads_table instead of GC_threads[hv]=me.
---

diff --git a/pthread_support.c b/pthread_support.c
index 9dc7ba56..ae262fde 100644
--- a/pthread_support.c
+++ b/pthread_support.c
@@ -737,6 +737,18 @@ GC_API void GC_CALL GC_register_altstack(void *stack, GC_word stack_size,
 }
 
 #ifdef CAN_HANDLE_FORK
+
+  /* Prevent TSan false positive about the race during items removal    */
+  /* from GC_threads.  (The race cannot happen since only one thread    */
+  /* survives in the child.)                                            */
+# ifdef CAN_CALL_ATFORK
+    GC_ATTR_NO_SANITIZE_THREAD
+# endif
+  static void store_to_threads_table(int hv, GC_thread me)
+  {
+    GC_threads[hv] = me;
+  }
+
 /* Remove all entries from the GC_threads table, except the     */
 /* one for the current thread.  We need to do this in the child */
 /* process after a fork(), since only the current thread        */
@@ -792,7 +804,7 @@ STATIC void GC_remove_all_threads_but_me(void)
           if (p != &first_thread) GC_INTERNAL_FREE(p);
         }
       }
-      GC_threads[hv] = me;
+      store_to_threads_table(hv, me);
     }
 }
 #endif /* CAN_HANDLE_FORK */