Add mono_gc_wbarrier_generic_store_atomic () function.

This is used in place of mono_gc_wbarrier_generic_store () when
we need the store to be atomic with release semantics.
(cherry picked from commit e4d2cc49a03b2cb7b31cddfd630e319bc4d344a1)

Conflicts:
	msvc/monosgen.def

8 files changed, 39 insertions, 4 deletions

diff --git a/docs/current-api b/docs/current-api
index d0efffcaba..1bbddca612 100644
--- a/docs/current-api
+++ b/docs/current-api
@@ -307,6 +307,7 @@ mono_gc_out_of_memory
 mono_gc_wbarrier_arrayref_copy
 mono_gc_wbarrier_generic_nostore
 mono_gc_wbarrier_generic_store
+mono_gc_wbarrier_generic_store_atomic
 mono_gc_wbarrier_object_copy
 mono_gc_wbarrier_set_arrayref
 mono_gc_wbarrier_set_field
diff --git a/docs/public-api b/docs/public-api
index 082bfd9fdd..231ecf171a 100644
--- a/docs/public-api
+++ b/docs/public-api
@@ -307,6 +307,7 @@ mono_gc_out_of_memory
 mono_gc_wbarrier_arrayref_copy
 mono_gc_wbarrier_generic_nostore
 mono_gc_wbarrier_generic_store
+mono_gc_wbarrier_generic_store_atomic
 mono_gc_wbarrier_object_copy
 mono_gc_wbarrier_set_arrayref
 mono_gc_wbarrier_set_field
diff --git a/mono/metadata/boehm-gc.c b/mono/metadata/boehm-gc.c
index 26665e50f5..0cb8292dcb 100644
--- a/mono/metadata/boehm-gc.c
+++ b/mono/metadata/boehm-gc.c
@@ -22,6 +22,7 @@
 #include <mono/metadata/marshal.h>
 #include <mono/metadata/runtime.h>
 #include <mono/utils/mono-logger-internal.h>
+#include <mono/utils/mono-memory-model.h>
 #include <mono/utils/mono-time.h>
 #include <mono/utils/mono-threads.h>
 #include <mono/utils/dtrace.h>
@@ -624,6 +625,12 @@ mono_gc_wbarrier_generic_store (gpointer ptr, MonoObject* value)
 }
 
 void
+mono_gc_wbarrier_generic_store_atomic (gpointer ptr, MonoObject *value)
+{
+	mono_atomic_store_release ((volatile MonoObject **) ptr, value);
+}
+
+void
 mono_gc_wbarrier_generic_nostore (gpointer ptr)
 {
 }
diff --git a/mono/metadata/null-gc.c b/mono/metadata/null-gc.c
index 13446ee0ec..0430dd5cbf 100644
--- a/mono/metadata/null-gc.c
+++ b/mono/metadata/null-gc.c
@@ -193,6 +193,12 @@ mono_gc_wbarrier_generic_store (gpointer ptr, MonoObject* value)
 }
 
 void
+mono_gc_wbarrier_generic_store_atomic (gpointer ptr, MonoObject *value)
+{
+	mono_atomic_store_release ((volatile MonoObject **) ptr, value);
+}
+
+void
 mono_gc_wbarrier_generic_nostore (gpointer ptr)
 {
 }
diff --git a/mono/metadata/object.h b/mono/metadata/object.h
index 70ff5814b3..959c09e49c 100644
--- a/mono/metadata/object.h
+++ b/mono/metadata/object.h
@@ -316,6 +316,7 @@ MONO_API void mono_gc_wbarrier_set_field     (MonoObject *obj, void* field_ptr,
 MONO_API void mono_gc_wbarrier_set_arrayref  (MonoArray *arr, void* slot_ptr, MonoObject* value);
 MONO_API void mono_gc_wbarrier_arrayref_copy (void* dest_ptr, void* src_ptr, int count);
 MONO_API void mono_gc_wbarrier_generic_store (void* ptr, MonoObject* value);
+MONO_API void mono_gc_wbarrier_generic_store_atomic (void *ptr, MonoObject *value);
 MONO_API void mono_gc_wbarrier_generic_nostore (void* ptr);
 MONO_API void mono_gc_wbarrier_value_copy    (void* dest, void* src, int count, MonoClass *klass);
 MONO_API void mono_gc_wbarrier_object_copy   (MonoObject* obj, MonoObject *src);
diff --git a/mono/metadata/sgen-gc.c b/mono/metadata/sgen-gc.c
index 8ce0994b50..2b6d1e3963 100644
--- a/mono/metadata/sgen-gc.c
+++ b/mono/metadata/sgen-gc.c
@@ -317,6 +317,7 @@ static int stat_wbarrier_set_field = 0;
 static int stat_wbarrier_set_arrayref = 0;
 static int stat_wbarrier_arrayref_copy = 0;
 static int stat_wbarrier_generic_store = 0;
+static int stat_wbarrier_generic_store_atomic = 0;
 static int stat_wbarrier_set_root = 0;
 static int stat_wbarrier_value_copy = 0;
 static int stat_wbarrier_object_copy = 0;
@@ -2217,6 +2218,7 @@ init_stats (void)
 	mono_counters_register ("WBarrier set arrayref", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_set_arrayref);
 	mono_counters_register ("WBarrier arrayref copy", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_arrayref_copy);
 	mono_counters_register ("WBarrier generic store called", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_generic_store);
+	mono_counters_register ("WBarrier generic atomic store called", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_generic_store_atomic);
 	mono_counters_register ("WBarrier set root", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_set_root);
 	mono_counters_register ("WBarrier value copy", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_value_copy);
 	mono_counters_register ("WBarrier object copy", MONO_COUNTER_GC | MONO_COUNTER_INT, &stat_wbarrier_object_copy);
@@ -4424,6 +4426,24 @@ mono_gc_wbarrier_generic_store (gpointer ptr, MonoObject* value)
 	sgen_dummy_use (value);
 }
 
+/* Same as mono_gc_wbarrier_generic_store () but performs the store
+ * as an atomic operation with release semantics.
+ */
+void
+mono_gc_wbarrier_generic_store_atomic (gpointer ptr, MonoObject *value)
+{
+	HEAVY_STAT (++stat_wbarrier_generic_store_atomic);
+
+	SGEN_LOG (8, "Wbarrier atomic store at %p to %p (%s)", ptr, value, value ? safe_name (value) : "null");
+
+	mono_atomic_store_release ((volatile MonoObject **) ptr, value);
+
+	if (ptr_in_nursery (value))
+		mono_gc_wbarrier_generic_nostore (ptr);
+
+	sgen_dummy_use (value);
+}
+
 void mono_gc_wbarrier_value_copy_bitmap (gpointer _dest, gpointer _src, int size, unsigned bitmap)
 {
 	mword *dest = _dest;
diff --git a/mono/metadata/threads.c b/mono/metadata/threads.c
index 7a00d1fbb9..59f8293f86 100755
--- a/mono/metadata/threads.c
+++ b/mono/metadata/threads.c
@@ -2490,8 +2490,7 @@ ves_icall_System_Threading_Thread_VolatileWriteIntPtr (void *ptr, void *value)
 void
 ves_icall_System_Threading_Thread_VolatileWriteObject (void *ptr, void *value)
 {
-	mono_atomic_store_release ((volatile MonoObject **) ptr, value);
-	mono_gc_wbarrier_generic_nostore (ptr);
+	mono_gc_wbarrier_generic_store_atomic (ptr, value);
 }
 
 void
@@ -2509,8 +2508,7 @@ ves_icall_System_Threading_Thread_VolatileWriteFloat (void *ptr, float value)
 void
 ves_icall_System_Threading_Volatile_Write_T (void *ptr, MonoObject *value)
 {
-	mono_atomic_store_release ((volatile MonoObject **) ptr, value);
-	mono_gc_wbarrier_generic_nostore (ptr);
+	mono_gc_wbarrier_generic_store_atomic (ptr, value);
 }
 
 void
diff --git a/msvc/mono.def b/msvc/mono.def
index 345a71e08b..7a264b225f 100644
--- a/msvc/mono.def
+++ b/msvc/mono.def
@@ -331,6 +331,7 @@ mono_gc_walk_heap
 mono_gc_wbarrier_arrayref_copy
 mono_gc_wbarrier_generic_nostore
 mono_gc_wbarrier_generic_store
+mono_gc_wbarrier_generic_store_atomic
 mono_gc_wbarrier_object_copy
 mono_gc_wbarrier_set_arrayref
 mono_gc_wbarrier_set_field