X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=include%2Furcu%2Farch%2Fgeneric.h;h=ac15a3bf7a378dab57cec797bb19a223fd10a634;hb=601922a81d884e16ff404cee7534ede56fb87d0a;hp=be6e41e24d88a40f16d07ae08d7d391aeb650821;hpb=86e8ab17bc98f890f7da1aa5af6ad9038820c618;p=userspace-rcu.git

diff --git a/include/urcu/arch/generic.h b/include/urcu/arch/generic.h
index be6e41e..ac15a3b 100644
--- a/include/urcu/arch/generic.h
+++ b/include/urcu/arch/generic.h
@@ -1,24 +1,12 @@
+// SPDX-FileCopyrightText: 2010 Paolo Bonzini <pbonzini@redhat.com>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
 #ifndef _URCU_ARCH_GENERIC_H
 #define _URCU_ARCH_GENERIC_H
 
 /*
  * arch_generic.h: common definitions for multiple architectures.
- *
- * Copyright (c) 2010 Paolo Bonzini <pbonzini@redhat.com>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <urcu/compiler.h>
@@ -43,6 +31,57 @@ extern "C" {
  * GCC builtins) as well as cmm_rmb and cmm_wmb (defaulting to cmm_mb).
  */
 
+#ifdef CONFIG_RCU_USE_ATOMIC_BUILTINS
+
+# ifdef CMM_SANITIZE_THREAD
+/*
+ * This makes TSAN quiet about unsupported thread fence.
+ */
+static inline void _cmm_thread_fence_wrapper(void)
+{
+#   if defined(__clang__)
+#    pragma clang diagnostic push
+#    pragma clang diagnostic ignored "-Wpragmas"
+#    pragma clang diagnostic ignored "-Wunknown-warning-option"
+#    pragma clang diagnostic ignored "-Wtsan"
+#   elif defined(__GNUC__)
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wpragmas"
+#    pragma GCC diagnostic ignored "-Wtsan"
+#   endif
+	__atomic_thread_fence(__ATOMIC_SEQ_CST);
+#   if defined(__clang__)
+#    pragma clang diagnostic pop
+#   elif defined(__GNUC__)
+#    pragma GCC diagnostic pop
+#   endif
+}
+# endif	 /* CMM_SANITIZE_THREAD */
+
+# ifndef cmm_smp_mb
+#  ifdef CMM_SANITIZE_THREAD
+#   define cmm_smp_mb() _cmm_thread_fence_wrapper()
+#  else
+#   define cmm_smp_mb() __atomic_thread_fence(__ATOMIC_SEQ_CST)
+#  endif /* CMM_SANITIZE_THREAD */
+# endif /* !cmm_smp_mb */
+
+#endif	/* CONFIG_RCU_USE_ATOMIC_BUILTINS */
+
+
+/*
+ * cmm_mb() expands to __sync_synchronize() instead of __atomic_thread_fence
+ * with SEQ_CST because the former "issues a full memory barrier" while the
+ * latter "acts as a synchronization fence between threads" which is too weak
+ * for what we want, for example with I/O devices.
+ *
+ * Even though sync_synchronize seems to be an alias for a sequential consistent
+ * atomic thread fence on every architecture on GCC and Clang, this assumption
+ * might be untrue in future.  Therefore, the definitions above are used to
+ * ensure correct behavior in the future.
+ *
+ * The above defintions are quoted from the GCC manual.
+ */
 #ifndef cmm_mb
 #define cmm_mb()    __sync_synchronize()
 #endif