Fix potential deadlock between AudioPolicyService and AudioSystem

Bug: 17109761
Change-Id: I315c1c5066f62b05e1c13b04fae1272b5fbce977

1 files changed, 5 insertions, 1 deletions

diff --git a/media/libmedia/AudioSystem.cpp b/media/libmedia/AudioSystem.cpp
index 3486d21..1742fbe 100644
--- a/media/libmedia/AudioSystem.cpp
+++ b/media/libmedia/AudioSystem.cpp
@@ -582,9 +582,13 @@ const sp<IAudioPolicyService>& AudioSystem::get_audio_policy_service()
         }
         binder->linkToDeath(gAudioPolicyServiceClient);
         gAudioPolicyService = interface_cast<IAudioPolicyService>(binder);
-        gAudioPolicyService->registerClient(gAudioPolicyServiceClient);
         gLock.unlock();
+        // Registering the client takes the AudioPolicyService lock.
+        // Don't hold the AudioSystem lock at the same time.
+        gAudioPolicyService->registerClient(gAudioPolicyServiceClient);
     } else {
+        // There exists a benign race condition where gAudioPolicyService
+        // is set, but gAudioPolicyServiceClient is not yet registered.
         gLock.unlock();
     }
     return gAudioPolicyService;