From b0bfe21abce7a1c51e356b81c8b9091e8fab4982 Mon Sep 17 00:00:00 2001
From: khizmax <khizmax@gmail.com>
Date: Mon, 24 Apr 2017 19:05:21 +0300
Subject: [PATCH] Restored acq-rel fence in urcu access_lock(). Seems, CLang
 3.6/3.7 cannot handle acquire barrier on atomic var correctly

---
 cds/urcu/details/gp.h | 5 +++++
 cds/urcu/details/sh.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/cds/urcu/details/gp.h b/cds/urcu/details/gp.h
index 41287a7d..eb43fc5f 100644
--- a/cds/urcu/details/gp.h
+++ b/cds/urcu/details/gp.h
@@ -70,8 +70,13 @@ namespace cds { namespace urcu { namespace details {
             pRec->m_nAccessControl.store( gp_singleton<RCUtag>::instance()->global_control_word(atomics::memory_order_relaxed),
                 atomics::memory_order_relaxed );
 
+#   if CDS_COMPILER == CDS_COMPILER_CLANG && CDS_COMPILER_VERSION < 30800
+            // Seems, CLang 3.6-3.7 cannot handle acquire barrier correctly
+            CDS_COMPILER_RW_BARRIER;
+#   else
             // acquire barrier
             pRec->m_nAccessControl.load( atomics::memory_order_acquire );
+#   endif
         }
         else {
             // nested lock
diff --git a/cds/urcu/details/sh.h b/cds/urcu/details/sh.h
index 8d0969f2..f02c37a4 100644
--- a/cds/urcu/details/sh.h
+++ b/cds/urcu/details/sh.h
@@ -74,8 +74,13 @@ namespace cds { namespace urcu { namespace details {
             pRec->m_nAccessControl.store( sh_singleton<RCUtag>::instance()->global_control_word(atomics::memory_order_relaxed),
                 atomics::memory_order_relaxed );
 
+#   if CDS_COMPILER == CDS_COMPILER_CLANG && CDS_COMPILER_VERSION < 30800
+            // Seems, CLang 3.6-3.7 cannot handle acquire barrier correctly
+            CDS_COMPILER_RW_BARRIER;
+#   else
             // acquire barrier
             pRec->m_nAccessControl.load( atomics::memory_order_acquire );
+#   endif
         }
         else {
             // nested lock
-- 
2.34.1