Use a lockless method for updating listener and context properties

This uses a separate container to provide the relevant properties to the
internal update method, using atomic pointer swaps. A free-list is used to
avoid having too many individual containers.

This allows the mixer to update the internal listener properties without
requiring the lock to protect against async updates. It also allows concurrent
read access to the user-facing property values, even the multi-value ones (e.g.
the vectors).

1 files changed, 31 insertions, 4 deletions

diff --git a/Alc/ALc.c b/Alc/ALc.c
index b8dae07c..058dd242 100644
--- a/Alc/ALc.c
+++ b/Alc/ALc.c
@@ -2064,7 +2064,6 @@ static ALCenum UpdateDeviceParams(ALCdevice *device, const ALCint *attrList)
     {
         ALsizei pos;
 
-        ATOMIC_STORE(&context->UpdateSources, AL_FALSE);
         LockUIntMapRead(&context->EffectSlotMap);
         for(pos = 0;pos < context->EffectSlotMap.size;pos++)
         {
@@ -2272,11 +2271,16 @@ static ALCboolean VerifyDevice(ALCdevice **device)
 static ALvoid InitContext(ALCcontext *Context)
 {
     ALlistener *listener = Context->Listener;
+
     //Initialise listener
     listener->Gain = 1.0f;
     listener->MetersPerUnit = 1.0f;
-    aluVectorSet(&listener->Position, 0.0f, 0.0f, 0.0f, 1.0f);
-    aluVectorSet(&listener->Velocity, 0.0f, 0.0f, 0.0f, 0.0f);
+    listener->Position[0] = 0.0f;
+    listener->Position[1] = 0.0f;
+    listener->Position[2] = 0.0f;
+    listener->Velocity[0] = 0.0f;
+    listener->Velocity[1] = 0.0f;
+    listener->Velocity[2] = 0.0f;
     listener->Forward[0] = 0.0f;
     listener->Forward[1] = 0.0f;
     listener->Forward[2] = -1.0f;
@@ -2296,9 +2300,12 @@ static ALvoid InitContext(ALCcontext *Context)
     listener->Params.DopplerFactor = 1.0f;
     listener->Params.SpeedOfSound = SPEEDOFSOUNDMETRESPERSEC;
 
+    ATOMIC_INIT(&listener->Update, NULL);
+    ATOMIC_INIT(&listener->FreeList, NULL);
+
     //Validate Context
+    RWLockInit(&Context->PropLock);
     ATOMIC_INIT(&Context->LastError, AL_NO_ERROR);
-    ATOMIC_INIT(&Context->UpdateSources, AL_FALSE);
     InitUIntMap(&Context->SourceMap, Context->Device->MaxNoOfSources);
     InitUIntMap(&Context->EffectSlotMap, Context->Device->AuxiliaryEffectSlotMax);
 
@@ -2321,6 +2328,10 @@ static ALvoid InitContext(ALCcontext *Context)
  */
 static void FreeContext(ALCcontext *context)
 {
+    ALlistener *listener = context->Listener;
+    struct ALlistenerProps *lprops;
+    size_t count;
+
     TRACE("%p\n", context);
 
     if(context->SourceMap.size > 0)
@@ -2344,6 +2355,22 @@ static void FreeContext(ALCcontext *context)
 
     VECTOR_DEINIT(context->ActiveAuxSlots);
 
+    if((lprops=ATOMIC_LOAD(&listener->Update, almemory_order_acquire)) != NULL)
+    {
+        TRACE("Freed unapplied listener update %p\n", lprops);
+        al_free(lprops);
+    }
+    count = 0;
+    lprops = ATOMIC_LOAD(&listener->FreeList, almemory_order_consume);
+    while(lprops)
+    {
+        struct ALlistenerProps *next = ATOMIC_LOAD(&lprops->next, almemory_order_consume);
+        al_free(lprops);
+        lprops = next;
+        ++count;
+    }
+    TRACE("Freed "SZFMT" listener property object%s\n", count, (count==1)?"":"s");
+
     ALCdevice_DecRef(context->Device);
     context->Device = NULL;