X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=include%2Furcu%2Farch%2Fgeneric.h;h=ac15a3bf7a378dab57cec797bb19a223fd10a634;hb=HEAD;hp=c02a6a9930d0b7126c24ac633b5995cfe18e6546;hpb=d3d3857f678627e7bbfb5a8d6f3bc15cd2a694d9;p=urcu.git

diff --git a/include/urcu/arch/generic.h b/include/urcu/arch/generic.h
index c02a6a9..ac15a3b 100644
--- a/include/urcu/arch/generic.h
+++ b/include/urcu/arch/generic.h
@@ -31,6 +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