diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 8866f5d..2d05a6d 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -2022,7 +2022,7 @@
     return NO_ERROR;
 }
 
-void AudioFlinger::closeOutputFinish(sp<PlaybackThread> thread)
+void AudioFlinger::closeOutputFinish(const sp<PlaybackThread>& thread)
 {
     AudioStreamOut *out = thread->clearOutput();
     ALOG_ASSERT(out != NULL, "out shouldn't be NULL");
@@ -2031,7 +2031,7 @@
     delete out;
 }
 
-void AudioFlinger::closeOutputInternal_l(sp<PlaybackThread> thread)
+void AudioFlinger::closeOutputInternal_l(const sp<PlaybackThread>& thread)
 {
     mPlaybackThreads.removeItem(thread->mId);
     thread->exit();
@@ -2292,7 +2292,7 @@
     return NO_ERROR;
 }
 
-void AudioFlinger::closeInputFinish(sp<RecordThread> thread)
+void AudioFlinger::closeInputFinish(const sp<RecordThread>& thread)
 {
     thread->exit();
     AudioStreamIn *in = thread->clearInput();
@@ -2302,7 +2302,7 @@
     delete in;
 }
 
-void AudioFlinger::closeInputInternal_l(sp<RecordThread> thread)
+void AudioFlinger::closeInputInternal_l(const sp<RecordThread>& thread)
 {
     mRecordThreads.removeItem(thread->mId);
     closeInputFinish(thread);
@@ -2558,7 +2558,7 @@
                                     audio_session_t triggerSession,
                                     audio_session_t listenerSession,
                                     sync_event_callback_t callBack,
-                                    wp<RefBase> cookie)
+                                    const wp<RefBase>& cookie)
 {
     Mutex::Autolock _l(mLock);