From 1936ffcb7b4acb98f435941db6423657e3d8c498 Mon Sep 17 00:00:00 2001
From: Ivan Maidanski <ivmai@mail.ru>
Date: Thu, 28 Dec 2017 11:04:40 +0300
Subject: [PATCH] Add assertion for suspend_ack_sem in start_world

This is to check that sem_post() is not called twice for a thread
(to stop) in GC_suspend_handler.

* pthread_stop_world.c [!NACL && GC_ASSERTIONS && !GC_OPENBSD_UTHREADS]
(GC_start_world): Add assertion that GC_suspend_ack_sem has zero value.
---
 pthread_stop_world.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pthread_stop_world.c b/pthread_stop_world.c
index 781c23b..6e9f406 100644
--- a/pthread_stop_world.c
+++ b/pthread_stop_world.c
@@ -1099,6 +1099,13 @@ GC_INNER void GC_start_world(void)
         }
       }
 #   endif
+#   if defined(GC_ASSERTIONS) && !defined(GC_OPENBSD_UTHREADS)
+      {
+        int ack_count;
+        sem_getvalue(&GC_suspend_ack_sem, &ack_count);
+        GC_ASSERT(0 == ack_count);
+      }
+#   endif
 #   ifdef DEBUG_THREADS
       GC_log_printf("World started\n");
 #   endif
-- 
2.7.4