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

3 files changed, 44 insertions, 22 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index d7eba154..b11a1c3a 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -978,14 +978,11 @@ ALvoid aluMixData(ALCdevice *device, ALvoid *buffer, ALsizei size)
         ctx = device->ContextList;
         while(ctx)
         {
-            ALboolean DeferUpdates = ctx->DeferUpdates;
-            ALboolean UpdateSources = AL_FALSE;
+            ALenum DeferUpdates = ctx->DeferUpdates;
+            ALenum UpdateSources = AL_FALSE;
 
             if(!DeferUpdates)
-            {
-                UpdateSources = ctx->UpdateSources;
-                ctx->UpdateSources = AL_FALSE;
-            }
+                UpdateSources = Exchange_ALenum(&ctx->UpdateSources, AL_FALSE);
 
             src = ctx->ActiveSources;
             src_end = src + ctx->ActiveSourceCount;
@@ -998,11 +995,9 @@ ALvoid aluMixData(ALCdevice *device, ALvoid *buffer, ALsizei size)
                     continue;
                 }
 
-                if(!DeferUpdates && ((*src)->NeedsUpdate || UpdateSources))
-                {
-                    (*src)->NeedsUpdate = AL_FALSE;
+                if(!DeferUpdates && (Exchange_ALenum(&(*src)->NeedsUpdate, AL_FALSE) ||
+                                     UpdateSources))
                     ALsource_Update(*src, ctx);
-                }
 
                 MixSource(*src, device, SamplesToDo);
                 src++;
@@ -1024,11 +1019,8 @@ ALvoid aluMixData(ALCdevice *device, ALvoid *buffer, ALsizei size)
                     ALEffectSlot->PendingClicks[i] = 0.0f;
                 }
 
-                if(!DeferUpdates && ALEffectSlot->NeedsUpdate)
-                {
-                    ALEffectSlot->NeedsUpdate = AL_FALSE;
+                if(!DeferUpdates && Exchange_ALenum(&ALEffectSlot->NeedsUpdate, AL_FALSE))
                     ALEffect_Update(ALEffectSlot->EffectState, ctx, ALEffectSlot);
-                }
 
                 ALEffect_Process(ALEffectSlot->EffectState, ALEffectSlot,
                                  SamplesToDo, ALEffectSlot->WetBuffer,
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);
-            }
         }
     }