audioflinger: Move async callback setting to onFirstRef
Since initializing async callback involves passing
PlaybackThread's 'this' around, it's safer to do that
in 'onFirstRef' instead of the constructor. Since
'onFirstRef' runs before the thread loop is started,
shared data access model is not affected.
Bug: 206737711
Test: atest CtsMediaAudioTestCases:AudioTrackOffloadTest
Test: check offloaded playback on the device
Change-Id: I26f76b9ff843c871911fe3546027cb197f1f0272
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 0de7e7d..00b612f 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -2140,9 +2140,19 @@
if (!isStreamInitialized()) {
ALOGE("The stream is not open yet"); // This should not happen.
} else {
- // setEventCallback will need a strong pointer as a parameter. Calling it
- // here instead of constructor of PlaybackThread so that the onFirstRef
- // callback would not be made on an incompletely constructed object.
+ // Callbacks take strong or weak pointers as a parameter.
+ // Since PlaybackThread passes itself as a callback handler, it can only
+ // be done outside of the constructor. Creating weak and especially strong
+ // pointers to a refcounted object in its own constructor is strongly
+ // discouraged, see comments in system/core/libutils/include/utils/RefBase.h.
+ // Even if a function takes a weak pointer, it is possible that it will
+ // need to convert it to a strong pointer down the line.
+ if (mOutput->flags & AUDIO_OUTPUT_FLAG_NON_BLOCKING &&
+ mOutput->stream->setCallback(this) == OK) {
+ mUseAsyncWrite = true;
+ mCallbackThread = new AudioFlinger::AsyncCallbackThread(this);
+ }
+
if (mOutput->stream->setEventCallback(this) != OK) {
ALOGD("Failed to add event callback");
}
@@ -3007,13 +3017,6 @@
mFrameCount);
}
- if (mOutput->flags & AUDIO_OUTPUT_FLAG_NON_BLOCKING) {
- if (mOutput->stream->setCallback(this) == OK) {
- mUseAsyncWrite = true;
- mCallbackThread = new AudioFlinger::AsyncCallbackThread(this);
- }
- }
-
mHwSupportsPause = false;
if (mOutput->flags & AUDIO_OUTPUT_FLAG_DIRECT) {
bool supportsPause = false, supportsResume = false;