audio: add mechanism to re-route nullified audio

Fixes a race condition whereby two requests attempt to change the audio stream
(and interrupt each other).  For example, a user space app makes a call through
the audio API and before completion, a kernel function such as jack removal is
detected and is serviced.  In this case, you have a nullified audio route that
needs to be re-routed.

In order to know a routing update is needed, a boolean member mForceRouting
has been introduced to enforce routing for the next attempt to set audio output
with a non-null device.

Change-Id: Ia0aa2f27fe63c39f0980dec2e1e79dbc26b81e56
Author: Vincent Becker <vincentx.becker@intel.com>
Signed-off-by: Vincent Becker <vincentx.becker@intel.com>
Signed-off-by: Zhi Jin <zhi.jin@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Signed-off-by: Robert Beatty <robert.m.beatty@intel.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/audio/AudioPolicyManagerBase.cpp b/audio/AudioPolicyManagerBase.cpp
index af24dbd..d62e733 100644
--- a/audio/AudioPolicyManagerBase.cpp
+++ b/audio/AudioPolicyManagerBase.cpp
@@ -2639,7 +2639,22 @@ uint32_t AudioPolicyManagerBase::setOutputDevice(audio_io_handle_t output,
 
     if (device != AUDIO_DEVICE_NONE) {
         outputDesc->mDevice = device;
+
+        // Force routing if previously asked for this output
+        if (outputDesc->mForceRouting) {
+            ALOGV("Force routing to current device as previous device was null for this output");
+            force = true;
+
+            // Request consumed. Reset mForceRouting to false
+            outputDesc->mForceRouting = false;
+        }
     }
+    else {
+        // Device is null and does not reflect the routing. Save the necessity to force
+        // re-routing upon next attempt to select a non-null device for this output
+        outputDesc->mForceRouting = true;
+    }
+
     muteWaitMs = checkDeviceMuteStrategies(outputDesc, prevDevice, delayMs);
 
     // Do not change the routing if:
@@ -3254,7 +3269,8 @@ AudioPolicyManagerBase::AudioOutputDescriptor::AudioOutputDescriptor(
     : mId(0), mSamplingRate(0), mFormat((audio_format_t)0),
       mChannelMask((audio_channel_mask_t)0), mLatency(0),
     mFlags((audio_output_flags_t)0), mDevice(AUDIO_DEVICE_NONE),
-    mOutput1(0), mOutput2(0), mProfile(profile), mDirectOpenCount(0)
+    mOutput1(0), mOutput2(0), mProfile(profile), mDirectOpenCount(0),
+    mForceRouting(false)
 {
     // clear usage count for all stream types
     for (int i = 0; i < AudioSystem::NUM_STREAM_TYPES; i++) {