commit a2ab4505c807f42afe34809409c4e85d91618a8c
author Eric Laurent <elaurent@google.com> Wed Sep 09 12:25:51 2015 -0700
committer Glenn Kasten <gkasten@google.com> Thu Sep 10 10:31:27 2015 -0700
tree cffdeb827eb93870aa692b8a9d3a0842ff8405de
parent 0f05031545e43c8fe49a9dda0cfd9dce202d1ef3

audio flinger: force audio path start from normal mixer

The audio HAL wakes up and configures the audio path when receiving
the first write() in standby state. This causes a certain amount of
process to take place in the mixer threads which is problematic for
fast mixer running at FIFO priority.

We now force a fake write() of 0 bytes from normal mixer to trigger
the audio path configuration before starting the fast mixer.

Bug: 23791972.

Change-Id: I54311b337fda956444846f5d2f53a3263d54e04b

services/audioflinger/Threads.cpp

diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 0a7d4a2..5bd9149 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -3479,6 +3479,12 @@
         if (state->mCommand != FastMixerState::MIX_WRITE &&
                 (kUseFastMixer != FastMixer_Dynamic || state->mTrackMask > 1)) {
             if (state->mCommand == FastMixerState::COLD_IDLE) {
+
+                // FIXME workaround for first HAL write being CPU bound on some devices
+                ATRACE_BEGIN("write");
+                mOutput->write((char *)mSinkBuffer, 0);
+                ATRACE_END();
+
                 int32_t old = android_atomic_inc(&mFastMixerFutex);
                 if (old == -1) {
                     (void) syscall(__NR_futex, &mFastMixerFutex, FUTEX_WAKE_PRIVATE, 1);