Radio: get service by value

Get strong pointer to service interface by value and not reference to
prevent race conditions where the service pointer can be cleared
by another thread while in use.

Bug: 30907212
Change-Id: Iae838b3b672562c1d0cd63968399a6bfdda7f5ab
(cherry picked from commit 28a0e9e)
(cherry picked from commit bd04b47d38a89f1dada1c6da2ef4a3d235c166b8)

include/radio/Radio.h

@@ -75,7 +75,7 @@ class Radio : public BnRadioClient,
 private:
             Radio(radio_handle_t handle,
                             const sp<RadioCallback>&);
-            static const sp<IRadioService>& getRadioService();
+            static const sp<IRadioService> getRadioService();
 
             Mutex                   mLock;
             sp<IRadio>              mIRadio;

radio/Radio.cpp

@@ -55,7 +55,7 @@ namespace {
     sp<DeathNotifier>         gDeathNotifier;
 }; // namespace anonymous
 
-const sp<IRadioService>& Radio::getRadioService()
+const sp<IRadioService> Radio::getRadioService()
 {
     Mutex::Autolock _l(gLock);
     if (gRadioService.get() == 0) {
@@ -84,7 +84,7 @@ status_t Radio::listModules(struct radio_properties *properties,
                             uint32_t *numModules)
 {
     ALOGV("listModules()");
-    const sp<IRadioService>& service = getRadioService();
+    const sp<IRadioService> service = getRadioService();
     if (service == 0) {
         return NO_INIT;
     }
@@ -98,7 +98,7 @@ sp<Radio> Radio::attach(radio_handle_t handle,
 {
     ALOGV("attach()");
     sp<Radio> radio;
-    const sp<IRadioService>& service = getRadioService();
+    const sp<IRadioService> service = getRadioService();
     if (service == 0) {
         return radio;
     }