Use atomic exchanges when checking for updates to objects' internal parameters

2 files changed, 38 insertions, 8 deletions

diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index 641baf7c..fa11a3d8 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -249,6 +249,12 @@ static __inline RefCount IncrementRef(volatile RefCount *ptr)
 static __inline RefCount DecrementRef(volatile RefCount *ptr)
 { return __sync_sub_and_fetch(ptr, 1); }
 
+#define DECL_TEMPLATE(T)                                                      \
+static __inline T Exchange_##T(volatile T *ptr, T newval)                     \
+{                                                                             \
+    return __sync_lock_test_and_set(ptr, newval);                             \
+}
+
 #elif defined(_WIN32)
 
 typedef LONG RefCount;
@@ -257,6 +263,16 @@ static __inline RefCount IncrementRef(volatile RefCount *ptr)
 static __inline RefCount DecrementRef(volatile RefCount *ptr)
 { return InterlockedDecrement(ptr); }
 
+#define DECL_TEMPLATE(T)                                                      \
+static __inline T Exchange_##T(volatile T *ptr, T newval)                     \
+{                                                                             \
+    union {                                                                   \
+        volatile T *t;                                                        \
+        volatile LONG *l;                                                     \
+    } u = { ptr };                                                            \
+    return InterlockedExchange(u.l, newval);                                  \
+}
+
 #elif defined(__APPLE__)
 
 #include <libkern/OSAtomic.h>
@@ -267,10 +283,29 @@ static __inline RefCount IncrementRef(volatile RefCount *ptr)
 static __inline RefCount DecrementRef(volatile RefCount *ptr)
 { return OSAtomicDecrement32Barrier(ptr); }
 
+#define DECL_TEMPLATE(T)                                                      \
+static __inline T Exchange_##T(volatile T *ptr, T newval)                     \
+{                                                                             \
+    union {                                                                   \
+        volatile T *t;                                                        \
+        volatile int32_t *l;                                                  \
+    } u = { ptr };                                                            \
+    /* Really? No regular old atomic swap? */                                 \
+    T oldval;                                                                 \
+    do {                                                                      \
+        oldval = *u.i;                                                        \
+    } while(!OSAtomicCompareAndSwap32Barrier(oldval, newval, u.i));           \
+    return oldval;                                                            \
+}
+
 #else
 #error "No atomic functions available on this platform!"
 #endif
 
+DECL_TEMPLATE(ALenum)
+
+#undef DECL_TEMPLATE
+
 
 #include "alListener.h"
 #include "alu.h"
diff --git a/OpenAL32/alState.c b/OpenAL32/alState.c
index 8e4c4671..7e73f407 100644
--- a/OpenAL32/alState.c
+++ b/OpenAL32/alState.c
@@ -604,22 +604,17 @@ AL_API ALvoid AL_APIENTRY alDeferUpdatesSOFT(void)
                 continue;
             }
 
-            if((*src)->NeedsUpdate || UpdateSources)
-            {
-                (*src)->NeedsUpdate = AL_FALSE;
+            if(Exchange_ALenum(&(*src)->NeedsUpdate, AL_FALSE) || UpdateSources)
                 ALsource_Update(*src, Context);
-            }
+
             src++;
         }
 
         for(e = 0;e < Context->EffectSlotMap.size;e++)
         {
             ALEffectSlot = Context->EffectSlotMap.array[e].value;
-            if(ALEffectSlot->NeedsUpdate)
-            {
-                ALEffectSlot->NeedsUpdate = AL_FALSE;
+            if(Exchange_ALenum(&ALEffectSlot->NeedsUpdate, AL_FALSE))
                 ALEffect_Update(ALEffectSlot->EffectState, Context, ALEffectSlot);
-            }
         }
     }