Re: [Sc-devel] [bug] possible race condition in server betweenSC_AudioDriver::RunThread()and ProcessOSCPacket()

["Ross Bencina" <rossb-lists@xxxxxxxxxxxxxx>]

Thanks James

> > #4 use a separate FIFO for sending OSC packets to the RT Engine. This 
> > would
> > mean zero interference with the scheduling of the NRT thread, and 
> > wouldn't
> > add much additional code (although it would lead to allocating another 
> > FIFO
> > buffer)...

> 4 is better in the long run.

Ok, I'll go with 4. I've made the patch below (not comitted). It adds a new 
mOscPacketsToEngine FIFO to SC_AudioDriver and the 
SendOscPacketMsgToEngine() member for enqueuing messages on it.

ProcessOSCPacket() has been modified to call SendOscPacketMsgToEngine.

Each AudioDriver's buffer processing routine has an added call to 
mOscPacketsToEngine.Perform();

I thought a little bit about whether to do:

mToEngine.Perform();
mOscPacketsToEngine.Perform();

or

mOscPacketsToEngine.Perform();
mToEngine.Perform();

Not sure there's a significant difference.

Shall I commit it?

In general I can't tell if there's any logic to the placement of the queues 
in AudioDriver but mDriverLock in mWorld rather than in AudioDriver.. is it 
just a legacy thing?

Ross.




Index: Headers/server/SC_CoreAudio.h
===================================================================
--- Headers/server/SC_CoreAudio.h       (revision 6865)
+++ Headers/server/SC_CoreAudio.h       (working copy)
@@ -95,6 +95,7 @@
       // Common members
       uint32  mHardwareBufferSize;    // bufferSize returned by 
kAudioDevicePropertyBufferSize
       EngineFifo mFromEngine, mToEngine;
+       EngineFifo mOscPacketsToEngine;
       SC_SyncCondition mAudioSync;
       pthread_t mThread;
       bool mRunThreadFlag;
@@ -147,9 +148,10 @@
               mPreferredSampleRate = inRate;
       }

-       bool SendMsgToEngine(FifoMsg& inMsg);
+       bool SendMsgToEngine(FifoMsg& inMsg);           // called by NRT 
thread
       bool SendMsgFromEngine(FifoMsg& inMsg);
-
+       bool SendOscPacketMsgToEngine(FifoMsg& inMsg);  // called by OSC 
socket listener threads, protected by mWorld->mDriverLock
+
       void AddEvent(SC_ScheduledEvent& event) { mScheduler.Add(event); }

       double GetAvgCPU() const { return mAvgCPU; }


Index: Source/server/SC_CoreAudio.cpp
===================================================================
--- Source/server/SC_CoreAudio.cpp      (revision 6865)
+++ Source/server/SC_CoreAudio.cpp      (working copy)
@@ -191,7 +191,7 @@
               inPacket->mIsBundle = 
gIsBundle.checkIsBundle((int32*)inPacket->mData);
               FifoMsg fifoMsg;
               fifoMsg.Set(inWorld, Perform_ToEngine_Msg, FreeOSCPacket, 
(void*)inPacket);
-               result = driver->SendMsgToEngine(fifoMsg);
+               result = driver->SendOscPacketMsgToEngine(fifoMsg);
       inWorld->mDriverLock->Unlock();
       return result;
}
@@ -389,6 +389,12 @@
       return mToEngine.Write(inMsg);
}

+bool SC_AudioDriver::SendOscPacketMsgToEngine(FifoMsg& inMsg)
+{
+       mOscPacketsToEngine.Free();
+       return mOscPacketsToEngine.Write(inMsg);
+}
+
void SC_ScheduledEvent::Perform()
{
       PerformOSCBundle(mWorld, mPacket);
@@ -910,6 +916,7 @@
                       scprintf("oscTime %.9f %.9f\n", oscTime*kOSCtoSecs, 
CoreAudioHostTimeToOSC(AudioGetCurrentHostTime())*kOSCtoSecs);
               }*/
               mToEngine.Perform();
+               mOscPacketsToEngine.Perform();

               int bufFrames = world->mBufLength;
               int numBufs = numSamplesPerCallback / bufFrames;
@@ -1565,6 +1572,7 @@

               mFromEngine.Free();
               mToEngine.Perform();
+               mOscPacketsToEngine.Perform();

               int numInputs = mInputChannelCount;
               int numOutputs = mOutputChannelCount;
@@ -1803,6 +1811,7 @@

               mFromEngine.Free();
               mToEngine.Perform();
+               mOscPacketsToEngine.Perform();

               int numInputs = mInputChannelCount;
               int numOutputs = mOutputChannelCount;