AAudio: Use futex for waitForStateChange
WaitForStateChange currently waits in twenty millisecond intervals
for state changes. This is clearly inefficient and if apps use this
consistently, much extra latency is added. This CL adds futexes so
the callback fires almost immediately after a state change.
This CL also changes updateStateMachine so updates from non-callbacks
do not happen if a callback thread is running.
Bug: 70722092
Test: atest AAudioTests
Test: Oboe automated tests (./run_tests.sh)
Test: OboeTester Plug Latency Test
Change-Id: I186dc9ddac7f3897d82a5ed0043a5f45f1c19fe3
diff --git a/media/libaaudio/src/client/AudioStreamInternal.cpp b/media/libaaudio/src/client/AudioStreamInternal.cpp
index 9f0564f..34ecd25 100644
--- a/media/libaaudio/src/client/AudioStreamInternal.cpp
+++ b/media/libaaudio/src/client/AudioStreamInternal.cpp
@@ -605,13 +605,6 @@
return AAUDIO_ERROR_INVALID_STATE;
}
-aaudio_result_t AudioStreamInternal::updateStateMachine() {
- if (isDataCallbackActive()) {
- return AAUDIO_OK; // state is getting updated by the callback thread read/write call
- }
- return processCommands();
-}
-
void AudioStreamInternal::logTimestamp(AAudioServiceMessage &command) {
static int64_t oldPosition = 0;
static int64_t oldTime = 0;
diff --git a/media/libaaudio/src/client/AudioStreamInternal.h b/media/libaaudio/src/client/AudioStreamInternal.h
index 2367572..4ea61d2 100644
--- a/media/libaaudio/src/client/AudioStreamInternal.h
+++ b/media/libaaudio/src/client/AudioStreamInternal.h
@@ -48,7 +48,7 @@
int64_t *framePosition,
int64_t *timeNanoseconds) override;
- virtual aaudio_result_t updateStateMachine() override;
+ virtual aaudio_result_t processCommands() override;
aaudio_result_t open(const AudioStreamBuilder &builder) override;
@@ -110,8 +110,6 @@
aaudio_result_t drainTimestampsFromService();
- aaudio_result_t processCommands();
-
aaudio_result_t stopCallback_l();
virtual void prepareBuffersForStart() {}
diff --git a/media/libaaudio/src/core/AudioStream.cpp b/media/libaaudio/src/core/AudioStream.cpp
index 06f05b0..8a5186a 100644
--- a/media/libaaudio/src/core/AudioStream.cpp
+++ b/media/libaaudio/src/core/AudioStream.cpp
@@ -21,7 +21,9 @@
#include <atomic>
#include <stdint.h>
+#include <linux/futex.h>
#include <media/MediaMetricsItem.h>
+#include <sys/syscall.h>
#include <aaudio/AAudio.h>
@@ -362,34 +364,37 @@
}
void AudioStream::setState(aaudio_stream_state_t state) {
- ALOGD("%s(s#%d) from %d to %d", __func__, getId(), mState, state);
- if (state == mState) {
+ aaudio_stream_state_t oldState = mState.load();
+ ALOGD("%s(s#%d) from %d to %d", __func__, getId(), oldState, state);
+ if (state == oldState) {
return; // no change
}
// Track transition to DISCONNECTED state.
if (state == AAUDIO_STREAM_STATE_DISCONNECTED) {
android::mediametrics::LogItem(mMetricsId)
.set(AMEDIAMETRICS_PROP_EVENT, AMEDIAMETRICS_PROP_EVENT_VALUE_DISCONNECT)
- .set(AMEDIAMETRICS_PROP_STATE, AudioGlobal_convertStreamStateToText(getState()))
+ .set(AMEDIAMETRICS_PROP_STATE, AudioGlobal_convertStreamStateToText(oldState))
.record();
}
// CLOSED is a final state
- if (mState == AAUDIO_STREAM_STATE_CLOSED) {
+ if (oldState == AAUDIO_STREAM_STATE_CLOSED) {
ALOGW("%s(%d) tried to set to %d but already CLOSED", __func__, getId(), state);
// Once CLOSING, we can only move to CLOSED state.
- } else if (mState == AAUDIO_STREAM_STATE_CLOSING
+ } else if (oldState == AAUDIO_STREAM_STATE_CLOSING
&& state != AAUDIO_STREAM_STATE_CLOSED) {
ALOGW("%s(%d) tried to set to %d but already CLOSING", __func__, getId(), state);
// Once DISCONNECTED, we can only move to CLOSING or CLOSED state.
- } else if (mState == AAUDIO_STREAM_STATE_DISCONNECTED
+ } else if (oldState == AAUDIO_STREAM_STATE_DISCONNECTED
&& !(state == AAUDIO_STREAM_STATE_CLOSING
|| state == AAUDIO_STREAM_STATE_CLOSED)) {
ALOGW("%s(%d) tried to set to %d but already DISCONNECTED", __func__, getId(), state);
} else {
- mState = state;
+ mState.store(state);
+ // Wake up a wakeForStateChange thread if it exists.
+ syscall(SYS_futex, &mState, FUTEX_WAKE_PRIVATE, INT_MAX, NULL, NULL, 0);
}
}
@@ -408,9 +413,15 @@
if (durationNanos > timeoutNanoseconds) {
durationNanos = timeoutNanoseconds;
}
- AudioClock::sleepForNanos(durationNanos);
- timeoutNanoseconds -= durationNanos;
+ struct timespec time;
+ time.tv_sec = durationNanos / AAUDIO_NANOS_PER_SECOND;
+ // Add the fractional nanoseconds.
+ time.tv_nsec = durationNanos - (time.tv_sec * AAUDIO_NANOS_PER_SECOND);
+ // Sleep for durationNanos. If mState changes from the callback
+ // thread, this thread will wake up earlier.
+ syscall(SYS_futex, &mState, FUTEX_WAIT_PRIVATE, currentState, &time, NULL, 0);
+ timeoutNanoseconds -= durationNanos;
aaudio_result_t result = updateStateMachine();
if (result != AAUDIO_OK) {
return result;
diff --git a/media/libaaudio/src/core/AudioStream.h b/media/libaaudio/src/core/AudioStream.h
index 5fb4528..8dd5538 100644
--- a/media/libaaudio/src/core/AudioStream.h
+++ b/media/libaaudio/src/core/AudioStream.h
@@ -100,10 +100,17 @@
int64_t *timeNanoseconds) = 0;
/**
- * Update state machine.()
- * @return
+ * Update state machine.
+ * @return result of the operation.
*/
- virtual aaudio_result_t updateStateMachine() = 0;
+ aaudio_result_t updateStateMachine() {
+ if (isDataCallbackActive()) {
+ return AAUDIO_OK; // state is getting updated by the callback thread read/write call
+ }
+ return processCommands();
+ };
+
+ virtual aaudio_result_t processCommands() = 0;
// =========== End ABSTRACT methods ===========================
@@ -184,7 +191,7 @@
// ============== Queries ===========================
aaudio_stream_state_t getState() const {
- return mState;
+ return mState.load();
}
virtual int32_t getBufferSize() const {
@@ -674,6 +681,8 @@
const android::sp<MyPlayerBase> mPlayerBase;
+ std::atomic<aaudio_stream_state_t> mState{AAUDIO_STREAM_STATE_UNINITIALIZED};
+
// These do not change after open().
int32_t mSamplesPerFrame = AAUDIO_UNSPECIFIED;
aaudio_channel_mask_t mChannelMask = AAUDIO_UNSPECIFIED;
@@ -682,7 +691,6 @@
aaudio_sharing_mode_t mSharingMode = AAUDIO_SHARING_MODE_SHARED;
bool mSharingModeMatchRequired = false; // must match sharing mode requested
audio_format_t mFormat = AUDIO_FORMAT_DEFAULT;
- aaudio_stream_state_t mState = AAUDIO_STREAM_STATE_UNINITIALIZED;
aaudio_performance_mode_t mPerformanceMode = AAUDIO_PERFORMANCE_MODE_NONE;
int32_t mFramesPerBurst = 0;
int32_t mBufferCapacity = 0;
diff --git a/media/libaaudio/src/legacy/AudioStreamLegacy.cpp b/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
index dd11169..f32ef65 100644
--- a/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
+++ b/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
@@ -127,7 +127,7 @@
mCallbackEnabled.store(false);
}
- if (updateStateMachine() != AAUDIO_OK) {
+ if (processCommands() != AAUDIO_OK) {
forceDisconnect();
mCallbackEnabled.store(false);
}
@@ -192,7 +192,7 @@
mCallbackEnabled.store(false);
}
- if (updateStateMachine() != AAUDIO_OK) {
+ if (processCommands() != AAUDIO_OK) {
forceDisconnect();
mCallbackEnabled.store(false);
}
diff --git a/media/libaaudio/src/legacy/AudioStreamRecord.cpp b/media/libaaudio/src/legacy/AudioStreamRecord.cpp
index 1e39e0f..9a136a7 100644
--- a/media/libaaudio/src/legacy/AudioStreamRecord.cpp
+++ b/media/libaaudio/src/legacy/AudioStreamRecord.cpp
@@ -364,8 +364,7 @@
return checkForDisconnectRequest(false);
}
-aaudio_result_t AudioStreamRecord::updateStateMachine()
-{
+aaudio_result_t AudioStreamRecord::processCommands() {
aaudio_result_t result = AAUDIO_OK;
aaudio_wrapping_frames_t position;
status_t err;
diff --git a/media/libaaudio/src/legacy/AudioStreamRecord.h b/media/libaaudio/src/legacy/AudioStreamRecord.h
index 5ce73f9..252ff3c 100644
--- a/media/libaaudio/src/legacy/AudioStreamRecord.h
+++ b/media/libaaudio/src/legacy/AudioStreamRecord.h
@@ -58,7 +58,7 @@
int64_t getFramesWritten() override;
- aaudio_result_t updateStateMachine() override;
+ aaudio_result_t processCommands() override;
aaudio_direction_t getDirection() const override {
return AAUDIO_DIRECTION_INPUT;
diff --git a/media/libaaudio/src/legacy/AudioStreamTrack.cpp b/media/libaaudio/src/legacy/AudioStreamTrack.cpp
index 6f1dc92..09caa5c 100644
--- a/media/libaaudio/src/legacy/AudioStreamTrack.cpp
+++ b/media/libaaudio/src/legacy/AudioStreamTrack.cpp
@@ -378,8 +378,7 @@
return checkForDisconnectRequest(false);;
}
-aaudio_result_t AudioStreamTrack::updateStateMachine()
-{
+aaudio_result_t AudioStreamTrack::processCommands() {
status_t err;
aaudio_wrapping_frames_t position;
switch (getState()) {
diff --git a/media/libaaudio/src/legacy/AudioStreamTrack.h b/media/libaaudio/src/legacy/AudioStreamTrack.h
index 0f4d72b..1f877b5 100644
--- a/media/libaaudio/src/legacy/AudioStreamTrack.h
+++ b/media/libaaudio/src/legacy/AudioStreamTrack.h
@@ -79,7 +79,7 @@
return AAUDIO_DIRECTION_OUTPUT;
}
- aaudio_result_t updateStateMachine() override;
+ aaudio_result_t processCommands() override;
int64_t incrementClientFrameCounter(int32_t frames) override {
return incrementFramesWritten(frames);