AudioFlinger: Associate audio time with client uid (2f366df6) · Commits · e / os / android_frameworks_av

services/audioflinger/Threads.cpp

+69 −125

Original line number	Diff line number	Diff line
		@@ -647,8 +647,7 @@ AudioFlinger::ThreadBase::ThreadBase(const sp<AudioFlinger>& audioFlinger, audio
		mAudioSource(AUDIO_SOURCE_DEFAULT), mId(id),
		// mName will be set by concrete (non-virtual) subclass
		mDeathRecipient(new PMDeathRecipient(this)),
		mSystemReady(systemReady),
		mNotifiedBatteryStart(false)
		mSystemReady(systemReady)
		{
		memset(&mPatch, 0, sizeof(struct audio_patch));
		}
		@@ -989,10 +988,10 @@ void AudioFlinger::ThreadBase::dumpEffectChains(int fd, const Vector<String16>&
		}
		}

		void AudioFlinger::ThreadBase::acquireWakeLock(int uid)
		void AudioFlinger::ThreadBase::acquireWakeLock()
		{
		Mutex::Autolock _l(mLock);
		acquireWakeLock_l(uid);
		acquireWakeLock_l();
		}

		String16 AudioFlinger::ThreadBase::getWakeLockTag()
		@@ -1014,37 +1013,23 @@ String16 AudioFlinger::ThreadBase::getWakeLockTag()
		}
		}

		void AudioFlinger::ThreadBase::acquireWakeLock_l(int uid)
		void AudioFlinger::ThreadBase::acquireWakeLock_l()
		{
		getPowerManager_l();
		if (mPowerManager != 0) {
		sp<IBinder> binder = new BBinder();
		status_t status;
		if (uid >= 0) {
		status = mPowerManager->acquireWakeLockWithUid(POWERMANAGER_PARTIAL_WAKE_LOCK,
		binder,
		getWakeLockTag(),
		String16("audioserver"),
		uid,
		true /* FIXME force oneway contrary to .aidl */);
		} else {
		status = mPowerManager->acquireWakeLock(POWERMANAGER_PARTIAL_WAKE_LOCK,
		// Uses AID_AUDIOSERVER for wakelock. updateWakeLockUids_l() updates with client uids.
		status_t status = mPowerManager->acquireWakeLock(POWERMANAGER_PARTIAL_WAKE_LOCK,
		binder,
		getWakeLockTag(),
		String16("audioserver"),
		true /* FIXME force oneway contrary to .aidl */);
		}
		if (status == NO_ERROR) {
		mWakeLockToken = binder;
		}
		ALOGV("acquireWakeLock_l() %s status %d", mThreadName, status);
		}

		if (!mNotifiedBatteryStart) {
		// TODO: call this function for each track when it becomes active.
		BatteryNotifier::getInstance().noteStartAudio(AID_AUDIOSERVER);
		mNotifiedBatteryStart = true;
		}
		gBoottime.acquire(mWakeLockToken);
		mTimestamp.mTimebaseOffset[ExtendedTimestamp::TIMEBASE_BOOTTIME] =
		gBoottime.getBoottimeOffset();
		@@ -1067,17 +1052,6 @@ void AudioFlinger::ThreadBase::releaseWakeLock_l()
		}
		mWakeLockToken.clear();
		}

		if (mNotifiedBatteryStart) {
		// TODO: call this function for each track when it becomes inactive.
		BatteryNotifier::getInstance().noteStopAudio(AID_AUDIOSERVER);
		mNotifiedBatteryStart = false;
		}
		}

		void AudioFlinger::ThreadBase::updateWakeLockUids(const SortedVector<int> &uids) {
		Mutex::Autolock _l(mLock);
		updateWakeLockUids_l(uids);
		}

		void AudioFlinger::ThreadBase::getPowerManager_l() {
		@@ -1096,6 +1070,15 @@ void AudioFlinger::ThreadBase::getPowerManager_l() {

		void AudioFlinger::ThreadBase::updateWakeLockUids_l(const SortedVector<int> &uids) {
		getPowerManager_l();

		#if !LOG_NDEBUG
		std::stringstream s;
		for (int uid : uids) {
		s << uid << " ";
		}
		ALOGD("updateWakeLockUids_l %s uids:%s", mThreadName, s.str().c_str());
		#endif

		if (mWakeLockToken == NULL) { // token may be NULL if AudioFlinger::systemReady() not called.
		if (mSystemReady) {
		ALOGE("no wake lock to update, but system ready!");
		@@ -1657,6 +1640,41 @@ void AudioFlinger::ThreadBase::systemReady()
		mPendingConfigEvents.clear();
		}

		template <typename T>
		ssize_t AudioFlinger::ThreadBase::ActiveTracks<T>::add(const sp<T> &track) {
		ssize_t index = mActiveTracks.indexOf(track);
		if (index >= 0) {
		ALOGW("ActiveTracks<T>::add track %p already there", track.get());
		return index;
		}
		mActiveTracksGeneration++;
		mLatestActiveTrack = track;
		BatteryNotifier::getInstance().noteStartAudio(track->uid());
		return mActiveTracks.add(track);
		}

		template <typename T>
		ssize_t AudioFlinger::ThreadBase::ActiveTracks<T>::remove(const sp<T> &track) {
		ssize_t index = mActiveTracks.remove(track);
		if (index < 0) {
		ALOGW("ActiveTracks<T>::remove nonexistent track %p", track.get());
		return index;
		}
		mActiveTracksGeneration++;
		BatteryNotifier::getInstance().noteStopAudio(track->uid());
		// mLatestActiveTrack is not cleared even if is the same as track.
		return index;
		}

		template <typename T>
		void AudioFlinger::ThreadBase::ActiveTracks<T>::clear() {
		for (const sp<T> &track : mActiveTracks) {
		BatteryNotifier::getInstance().noteStopAudio(track->uid());
		}
		mLastActiveTracksGeneration = mActiveTracksGeneration;
		mActiveTracks.clear();
		mLatestActiveTrack.clear();
		}

		// ----------------------------------------------------------------------------
		// Playback
		@@ -1683,7 +1701,6 @@ AudioFlinger::PlaybackThread::PlaybackThread(const sp<AudioFlinger>& audioFlinge
		mSuspended(0), mBytesWritten(0),
		mFramesWritten(0),
		mSuspendedFrames(0),
		mActiveTracksGeneration(0),
		// mStreamTypes[] initialized in constructor body
		mOutput(output),
		mLastWriteTime(-1), mNumWrites(0), mNumDelayedWrites(0), mInWrite(false),
		@@ -1802,8 +1819,8 @@ void AudioFlinger::PlaybackThread::dumpTracks(int fd, const Vector<String16>& ar
		result.append(buffer);
		Track::appendDumpHeader(result);
		for (size_t i = 0; i < numactive; ++i) {
		sp<Track> track = mActiveTracks[i].promote();
		if (track != 0 && mTracks.indexOf(track) < 0) {
		sp<Track> track = mActiveTracks[i];
		if (mTracks.indexOf(track) < 0) {
		track->dump(buffer, SIZE, true);
		result.append(buffer);
		}
		@@ -2206,9 +2223,6 @@ status_t AudioFlinger::PlaybackThread::addTrack_l(const sp<Track>& track)
		track->mResetDone = false;
		track->mPresentationCompleteFrames = 0;
		mActiveTracks.add(track);
		mWakeLockUids.add(track->uid());
		mActiveTracksGeneration++;
		mLatestActiveTrack = track;
		sp<EffectChain> chain = getEffectChain_l(track->sessionId());
		if (chain != 0) {
		ALOGV("addTrack_l() starting track on chain %p for session %d", chain.get(),
		@@ -2843,11 +2857,7 @@ status_t AudioFlinger::PlaybackThread::addEffectChain_l(const sp<EffectChain>& c
		}

		// indicate all active tracks in the chain
		for (size_t i = 0 ; i < mActiveTracks.size() ; ++i) {
		sp<Track> track = mActiveTracks[i].promote();
		if (track == 0) {
		continue;
		}
		for (const sp<Track> &track : mActiveTracks) {
		if (session == track->sessionId()) {
		ALOGV("addEffectChain_l() activating track %p on session %d", track.get(), session);
		chain->incActiveTrackCnt();
		@@ -2894,11 +2904,7 @@ size_t AudioFlinger::PlaybackThread::removeEffectChain_l(const sp<EffectChain>&
		if (chain == mEffectChains[i]) {
		mEffectChains.removeAt(i);
		// detach all active tracks from the chain
		for (size_t i = 0 ; i < mActiveTracks.size() ; ++i) {
		sp<Track> track = mActiveTracks[i].promote();
		if (track == 0) {
		continue;
		}
		for (const sp<Track> &track : mActiveTracks) {
		if (session == track->sessionId()) {
		ALOGV("removeEffectChain_l(): stopping track on chain %p for session Id: %d",
		chain.get(), session);
		@@ -2975,8 +2981,6 @@ bool AudioFlinger::PlaybackThread::threadLoop()
		// FIXME could this be made local to while loop?
		writeFrames = 0;

		int lastGeneration = 0;

		cacheParameters_l();
		mSleepTimeUs = mIdleSleepTimeUs;

		@@ -3074,10 +3078,9 @@ bool AudioFlinger::PlaybackThread::threadLoop()
		mTimestamp.mTimeNs[ExtendedTimestamp::LOCATION_SERVER] = mLastWriteTime == -1
		? systemTime() : mLastWriteTime;
		}
		const size_t size = mActiveTracks.size();
		for (size_t i = 0; i < size; ++i) {
		sp<Track> t = mActiveTracks[i].promote();
		if (t != 0 && !t->isFastTrack()) {

		for (const sp<Track> &t : mActiveTracks) {
		if (!t->isFastTrack()) {
		t->updateTrackFrameInfo(
		t->mAudioTrackServerProxy->framesReleased(),
		mFramesWritten,
		@@ -3098,8 +3101,6 @@ bool AudioFlinger::PlaybackThread::threadLoop()
		if (!keepWakeLock()) {
		releaseWakeLock_l();
		released = true;
		mWakeLockUids.clear();
		mActiveTracksGeneration++;
		}
		ALOGV("wait async completion");
		mWaitWorkCV.wait(mLock);
		@@ -3133,8 +3134,6 @@ bool AudioFlinger::PlaybackThread::threadLoop()
		}

		releaseWakeLock_l();
		mWakeLockUids.clear();
		mActiveTracksGeneration++;
		// wait until we have something to do...
		ALOGV("%s going to sleep", myName.string());
		mWaitWorkCV.wait(mLock);
		@@ -3159,12 +3158,7 @@ bool AudioFlinger::PlaybackThread::threadLoop()
		// mMixerStatusIgnoringFastTracks is also updated internally
		mMixerStatus = prepareTracks_l(&tracksToRemove);

		// compare with previously applied list
		if (lastGeneration != mActiveTracksGeneration) {
		// update wakelock
		updateWakeLockUids_l(mWakeLockUids);
		lastGeneration = mActiveTracksGeneration;
		}
		mActiveTracks.updateWakeLockUids(this);

		// prevent any changes in effect chain list and in each effect chain
		// during mixing and effect process as the audio buffers could be deleted
		@@ -3382,8 +3376,6 @@ bool AudioFlinger::PlaybackThread::threadLoop()
		}

		releaseWakeLock();
		mWakeLockUids.clear();
		mActiveTracksGeneration++;

		ALOGV("Thread %p type %d exiting", this, mType);
		return false;
		@@ -3397,8 +3389,6 @@ void AudioFlinger::PlaybackThread::removeTracks_l(const Vector< sp<Track> >& tra
		for (size_t i=0 ; i<count ; i++) {
		const sp<Track>& track = tracksToRemove.itemAt(i);
		mActiveTracks.remove(track);
		mWakeLockUids.remove(track->uid());
		mActiveTracksGeneration++;
		ALOGV("removeTracks_l removing track on session %d", track->sessionId());
		sp<EffectChain> chain = getEffectChain_l(track->sessionId());
		if (chain != 0) {
		@@ -4017,10 +4007,7 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::MixerThread::prepareTrac
		mEffectBufferValid = false; // mEffectBuffer has no valid data until tracks found.

		for (size_t i=0 ; i<count ; i++) {
		const sp<Track> t = mActiveTracks[i].promote();
		if (t == 0) {
		continue;
		}
		const sp<Track> t = mActiveTracks[i];

		// this const just means the local variable doesn't change
		Track* const track = t.get();
		@@ -4516,11 +4503,7 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::MixerThread::prepareTrac
		size_t i = __builtin_ctz(resetMask);
		ALOG_ASSERT(i < count);
		resetMask &= ~(1 << i);
		sp<Track> t = mActiveTracks[i].promote();
		if (t == 0) {
		continue;
		}
		Track* track = t.get();
		sp<Track> track = mActiveTracks[i];
		ALOG_ASSERT(track->isFastTrack() && track->isStopped());
		track->reset();
		}
		@@ -4830,7 +4813,7 @@ void AudioFlinger::DirectOutputThread::processVolume_l(Track *track, bool lastTr
		void AudioFlinger::DirectOutputThread::onAddNewTrack_l()
		{
		sp<Track> previousTrack = mPreviousTrack.promote();
		sp<Track> latestTrack = mLatestActiveTrack.promote();
		sp<Track> latestTrack = mActiveTracks.getLatest();

		if (previousTrack != 0 && latestTrack != 0) {
		if (mType == DIRECT) {
		@@ -4856,13 +4839,7 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::DirectOutputThread::prep
		bool doHwResume = false;

		// find out which tracks need to be processed
		for (size_t i = 0; i < count; i++) {
		sp<Track> t = mActiveTracks[i].promote();
		// The track died recently
		if (t == 0) {
		continue;
		}

		for (const sp<Track> &t : mActiveTracks) {
		if (t->isInvalid()) {
		ALOGW("An invalidated track shouldn't be in active list");
		tracksToRemove->add(t);
		@@ -4877,7 +4854,7 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::DirectOutputThread::prep
		// In theory an older track could underrun and restart after the new one starts
		// but as we only care about the transition phase between two tracks on a
		// direct output, it is not a problem to ignore the underrun case.
		sp<Track> l = mLatestActiveTrack.promote();
		sp<Track> l = mActiveTracks.getLatest();
		bool last = l.get() == track;

		if (track->isPausing()) {
		@@ -5411,12 +5388,7 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::OffloadThread::prepareTr
		ALOGV("OffloadThread::prepareTracks_l active tracks %zu", count);

		// find out which tracks need to be processed
		for (size_t i = 0; i < count; i++) {
		sp<Track> t = mActiveTracks[i].promote();
		// The track died recently
		if (t == 0) {
		continue;
		}
		for (const sp<Track> &t : mActiveTracks) {
		Track* const track = t.get();
		#ifdef VERY_VERY_VERBOSE_LOGGING
		audio_track_cblk_t* cblk = track->cblk();
		@@ -5425,7 +5397,7 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::OffloadThread::prepareTr
		// In theory an older track could underrun and restart after the new one starts
		// but as we only care about the transition phase between two tracks on a
		// direct output, it is not a problem to ignore the underrun case.
		sp<Track> l = mLatestActiveTrack.promote();
		sp<Track> l = mActiveTracks.getLatest();
		bool last = l.get() == track;

		if (track->isInvalid()) {
		@@ -5884,7 +5856,7 @@ AudioFlinger::RecordThread::RecordThread(const sp<AudioFlinger>& audioFlinger,
		#endif
		) :
		ThreadBase(audioFlinger, id, outDevice, inDevice, RECORD, systemReady),
		mInput(input), mActiveTracksGen(0), mRsmpInBuffer(NULL),
		mInput(input), mRsmpInBuffer(NULL),
		// mRsmpInFrames, mRsmpInFramesP2, and mRsmpInFramesOA are set by readInputParameters_l()
		mRsmpInRear(0)
		#ifdef TEE_SINK
		@@ -6042,25 +6014,9 @@ bool AudioFlinger::RecordThread::threadLoop()

		reacquire_wakelock:
		sp<RecordTrack> activeTrack;
		int activeTracksGen;
		{
		Mutex::Autolock _l(mLock);
		size_t size = mActiveTracks.size();
		activeTracksGen = mActiveTracksGen;
		if (size > 0) {
		// FIXME an arbitrary choice
		activeTrack = mActiveTracks[0];
		acquireWakeLock_l(activeTrack->uid());
		if (size > 1) {
		SortedVector<int> tmp;
		for (size_t i = 0; i < size; i++) {
		tmp.add(mActiveTracks[i]->uid());
		}
		updateWakeLockUids_l(tmp);
		}
		} else {
		acquireWakeLock_l(-1);
		}
		acquireWakeLock_l();
		}

		// used to request a deferred sleep, to be executed later while mutex is unlocked
		@@ -6112,15 +6068,6 @@ reacquire_wakelock:
		goto reacquire_wakelock;
		}

		if (mActiveTracksGen != activeTracksGen) {
		activeTracksGen = mActiveTracksGen;
		SortedVector<int> tmp;
		for (size_t i = 0; i < size; i++) {
		tmp.add(mActiveTracks[i]->uid());
		}
		updateWakeLockUids_l(tmp);
		}

		bool doBroadcast = false;
		bool allStopped = true;
		for (size_t i = 0; i < size; ) {
		@@ -6133,7 +6080,6 @@ reacquire_wakelock:
		}
		removeTrack_l(activeTrack);
		mActiveTracks.remove(activeTrack);
		mActiveTracksGen++;
		size--;
		continue;
		}
		@@ -6143,7 +6089,6 @@ reacquire_wakelock:

		case TrackBase::PAUSING:
		mActiveTracks.remove(activeTrack);
		mActiveTracksGen++;
		doBroadcast = true;
		size--;
		continue;
		@@ -6183,6 +6128,8 @@ reacquire_wakelock:
		}
		}

		mActiveTracks.updateWakeLockUids(this);

		if (allStopped) {
		standbyIfNotAlreadyInStandby();
		}
		@@ -6481,7 +6428,6 @@ unlock:
		track->invalidate();
		}
		mActiveTracks.clear();
		mActiveTracksGen++;
		mStartStopCond.broadcast();
		}

		@@ -6735,7 +6681,6 @@ status_t AudioFlinger::RecordThread::start(RecordThread::RecordTrack* recordTrac
		// or using a separate command thread
		recordTrack->mState = TrackBase::STARTING_1;
		mActiveTracks.add(recordTrack);
		mActiveTracksGen++;
		status_t status = NO_ERROR;
		if (recordTrack->isExternalTrack()) {
		mLock.unlock();
		@@ -6744,7 +6689,6 @@ status_t AudioFlinger::RecordThread::start(RecordThread::RecordTrack* recordTrac
		// FIXME should verify that recordTrack is still in mActiveTracks
		if (status != NO_ERROR) {
		mActiveTracks.remove(recordTrack);
		mActiveTracksGen++;
		recordTrack->clearSyncStartEvent();
		ALOGV("RecordThread::start error %d", status);
		return status;

services/audioflinger/Threads.h

+97 −13

Original line number	Diff line number	Diff line
		@@ -400,11 +400,10 @@ protected:
		effect_uuid_t mType; // effect type UUID
		};

		void acquireWakeLock(int uid = -1);
		virtual void acquireWakeLock_l(int uid = -1);
		void acquireWakeLock();
		virtual void acquireWakeLock_l();
		void releaseWakeLock();
		void releaseWakeLock_l();
		void updateWakeLockUids(const SortedVector<int> &uids);
		void updateWakeLockUids_l(const SortedVector<int> &uids);
		void getPowerManager_l();
		void setEffectSuspended_l(const effect_uuid_t *type,
		@@ -479,8 +478,88 @@ protected:
		static const size_t kLogSize = 4 * 1024;
		sp<NBLog::Writer> mNBLogWriter;
		bool mSystemReady;
		bool mNotifiedBatteryStart;
		ExtendedTimestamp mTimestamp;

		// ActiveTracks is a sorted vector of track type T representing the
		// active tracks of threadLoop() to be considered by the locked prepare portion.
		// ActiveTracks should be accessed with the ThreadBase lock held.
		//
		// During processing and I/O, the threadLoop does not hold the lock;
		// hence it does not directly use ActiveTracks. Care should be taken
		// to hold local strong references or defer removal of tracks
		// if the threadLoop may still be accessing those tracks due to mix, etc.
		//
		// This class updates power information appropriately.
		//

		template <typename T>
		class ActiveTracks {
		public:
		ActiveTracks()
		: mActiveTracksGeneration(0)
		, mLastActiveTracksGeneration(0)
		{ }

		~ActiveTracks() {
		clear();
		}
		// returns the last track added (even though it may have been
		// subsequently removed from ActiveTracks).
		//
		// Used for DirectOutputThread to ensure a flush is called when transitioning
		// to a new track (even though it may be on the same session).
		// Used for OffloadThread to ensure that volume and mixer state is
		// taken from the latest track added.
		//
		// The latest track is saved with a weak pointer to prevent keeping an
		// otherwise useless track alive. Thus the function will return nullptr
		// if the latest track has subsequently been removed and destroyed.
		sp<T> getLatest() {
		return mLatestActiveTrack.promote();
		}

		// Updates ActiveTracks client uids to the thread wakelock.
		void updateWakeLockUids(sp<ThreadBase> thread, bool force = false) {
		if (mActiveTracksGeneration != mLastActiveTracksGeneration \|\| force) {
		thread->updateWakeLockUids_l(getWakeLockUids());
		mLastActiveTracksGeneration = mActiveTracksGeneration;
		}
		}

		// SortedVector methods
		ssize_t add(const sp<T> &track);
		ssize_t remove(const sp<T> &track);
		size_t size() const {
		return mActiveTracks.size();
		}
		ssize_t indexOf(const sp<T>& item) {
		return mActiveTracks.indexOf(item);
		}
		sp<T> operator[](size_t index) const {
		return mActiveTracks[index];
		}
		typename SortedVector<sp<T>>::iterator begin() {
		return mActiveTracks.begin();
		}
		typename SortedVector<sp<T>>::iterator end() {
		return mActiveTracks.end();
		}
		void clear();

		private:
		SortedVector<int> getWakeLockUids() {
		SortedVector<int> wakeLockUids;
		for (const sp<T> &track : mActiveTracks) {
		wakeLockUids.add(track->uid());
		}
		return wakeLockUids; // moved by underlying SharedBuffer
		}

		SortedVector<sp<T>> mActiveTracks;
		int mActiveTracksGeneration;
		int mLastActiveTracksGeneration;
		wp<T> mLatestActiveTrack; // latest track added to ActiveTracks
		};
		};

		// --- PlaybackThread ---
		@@ -559,6 +638,10 @@ protected:
		virtual void preExit();

		virtual bool keepWakeLock() const { return true; }
		virtual void acquireWakeLock_l() {
		ThreadBase::acquireWakeLock_l();
		mActiveTracks.updateWakeLockUids(this, true /* force */);
		}

		public:

		@@ -731,10 +814,7 @@ private:
		bool mMasterMute;
		void setMasterMute_l(bool muted) { mMasterMute = muted; }
		protected:
		SortedVector< wp<Track> > mActiveTracks; // FIXME check if this could be sp<>
		SortedVector<int> mWakeLockUids;
		int mActiveTracksGeneration;
		wp<Track> mLatestActiveTrack; // latest track added to mActiveTracks
		ActiveTracks<Track> mActiveTracks;

		// Allocate a track name for a given channel mask.
		// Returns name >= 0 if successful, -1 on failure.
		@@ -900,8 +980,8 @@ protected:
		virtual uint32_t suspendSleepTimeUs() const;
		virtual void cacheParameters_l();

		virtual void acquireWakeLock_l(int uid = -1) {
		PlaybackThread::acquireWakeLock_l(uid);
		virtual void acquireWakeLock_l() {
		PlaybackThread::acquireWakeLock_l();
		if (hasFastMixer()) {
		mFastMixer->setBoottimeOffset(
		mTimestamp.mTimebaseOffset[ExtendedTimestamp::TIMEBASE_BOOTTIME]);
		@@ -1340,6 +1420,11 @@ public:
		virtual status_t checkEffectCompatibility_l(const effect_descriptor_t *desc,
		audio_session_t sessionId);

		virtual void acquireWakeLock_l() {
		ThreadBase::acquireWakeLock_l();
		mActiveTracks.updateWakeLockUids(this, true /* force */);
		}

		private:
		// Enter standby if not already in standby, and set mStandby flag
		void standbyIfNotAlreadyInStandby();
		@@ -1351,9 +1436,8 @@ private:
		SortedVector < sp<RecordTrack> > mTracks;
		// mActiveTracks has dual roles: it indicates the current active track(s), and
		// is used together with mStartStopCond to indicate start()/stop() progress
		SortedVector< sp<RecordTrack> > mActiveTracks;
		// generation counter for mActiveTracks
		int mActiveTracksGen;
		ActiveTracks<RecordTrack> mActiveTracks;

		Condition mStartStopCond;

		// resampler converts input at HAL Hz to output at AudioRecord client Hz