AudioFlinger: offload playback, non-blocking write

- Added specialized playback thread class for offload playback,
derived from directoutput thread.
This thread type handles specific state transitions for offloaded
tracks and offloading commands (pause/resume/drain/flush..) to audio HAL.
As opposed to other threads, does not go to standby if the track is paused.

- Added support for asynchronous write and drain operations at audio HAL.
Use a thread to handle async callback events from HAL: this avoids locking
playback thread mutex when executing the callback and cause deadlocks when
calling audio HAL functions with the playback thread mutex locked.

- Better accouting for track activity: call start/stop and release Output
methods in audio policy manager when tracks are actually added and removed
from the active tracks list.
Added a command thread in audio policy service to handle stop/release commands
asynchronously and avoid deadlocks with playback thread.

- Track terminated status is not a state anymore. This condition is othogonal
to state to permitted state transitions while terminated.

Change-Id: Id157f4b3277620568d8eace7535d9186602564de

1 files changed, 9 insertions, 4 deletions

diff --git a/services/audioflinger/TrackBase.h b/services/audioflinger/TrackBase.h
index 55d96fa..e69d1d7 100644
--- a/services/audioflinger/TrackBase.h
+++ b/services/audioflinger/TrackBase.h
@@ -25,10 +25,10 @@ class TrackBase : public ExtendedAudioBufferProvider, public RefBase {
 public:
     enum track_state {
         IDLE,
-        TERMINATED,
         FLUSHED,
         STOPPED,
-        // next 2 states are currently used for fast tracks only
+        // next 2 states are currently used for fast tracks
+        // and offloaded tracks only
         STOPPING_1,     // waiting for first underrun
         STOPPING_2,     // waiting for presentation complete
         RESUMING,
@@ -89,7 +89,7 @@ protected:
         return (mState == STOPPED || mState == FLUSHED);
     }
 
-    // for fast tracks only
+    // for fast tracks and offloaded tracks only
     bool isStopping() const {
         return mState == STOPPING_1 || mState == STOPPING_2;
     }
@@ -101,7 +101,11 @@ protected:
     }
 
     bool isTerminated() const {
-        return mState == TERMINATED;
+        return mTerminated;
+    }
+
+    void terminate() {
+        mTerminated = true;
     }
 
     bool step();    // mStepCount is an implicit input
@@ -142,4 +146,5 @@ protected:
     const int           mId;
     sp<NBAIO_Sink>      mTeeSink;
     sp<NBAIO_Source>    mTeeSource;
+    bool                mTerminated;
 };