Resubmit fix for undefined mutex behavior in Admob destructor on Android.

originally sumbitted as cl/279825051

Tests run are implemented using pthread and are executed and built only on phones.

PiperOrigin-RevId: 281148306

Author: Googler

admob/src/android/banner_view_internal_android.cc

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+#include "admob/src/android/banner_view_internal_android.h"
+
 #include <assert.h>
 #include <jni.h>
 
@@ -23,13 +25,13 @@
 #include "admob/admob_resources.h"
 #include "admob/src/android/ad_request_converter.h"
 #include "admob/src/android/admob_android.h"
-#include "admob/src/android/banner_view_internal_android.h"
 #include "admob/src/common/admob_common.h"
 #include "admob/src/include/firebase/admob.h"
 #include "admob/src/include/firebase/admob/banner_view.h"
 #include "admob/src/include/firebase/admob/types.h"
 #include "app/src/assert.h"
 #include "app/src/mutex.h"
+#include "app/src/semaphore.h"
 #include "app/src/util_android.h"
 
 namespace firebase {
@@ -56,24 +58,25 @@ BannerViewInternalAndroid::BannerViewInternalAndroid(BannerView* base)
   env->DeleteLocalRef(helper_ref);
 }
 
+
+void DestroyOnDeleteCallback(const Future<void>& result,
+                          void* sem_data) {
+  if (sem_data != nullptr) {
+    Semaphore* semaphore =  static_cast<Semaphore*>(sem_data);
+    semaphore->Post();
+  }
+}
+
 BannerViewInternalAndroid::~BannerViewInternalAndroid() {
   JNIEnv* env = ::firebase::admob::GetJNI();
 
-  // Destroy the banner view so all pending futures / callbacks complete.
-  {
-    Mutex mutex(Mutex::kModeNonRecursive);
-    mutex.Acquire();
-    Destroy().OnCompletion(
-        [](const Future<void>&, void* mutex) {
-          reinterpret_cast<Mutex*>(mutex)->Release();
-        },
-        &mutex);
-    // Acquire a second Mutex lock to block until the Future for the last call
-    // to Destroy() completes at which point the lambda function in OnCompletion
-    // is called and the Mutex lock is released.
-    mutex.Acquire();
-    mutex.Release();
-  }
+  DestroyInternalData();
+
+  Semaphore semaphore(0);
+  InvokeNullary(kBannerViewFnDestroyOnDelete, banner_view_helper::kDestroy)
+      .OnCompletion(DestroyOnDeleteCallback, &semaphore);
+
+  semaphore.Wait();
   env->DeleteGlobalRef(helper_);
   helper_ = nullptr;
 }
@@ -131,8 +134,7 @@ Future<void> BannerViewInternalAndroid::Resume() {
 }
 
 Future<void> BannerViewInternalAndroid::Destroy() {
-  // The bounding box is zeroed on destroy.
-  bounding_box_ = {};
+  DestroyInternalData();
   return InvokeNullary(kBannerViewFnDestroy, banner_view_helper::kDestroy);
 }
 
@@ -214,6 +216,11 @@ Future<void> BannerViewInternalAndroid::InvokeNullary(
   return GetLastResult(fn);
 }
 
+void BannerViewInternalAndroid::DestroyInternalData() {
+  // The bounding box is zeroed on destroy.
+  bounding_box_ = {};
+}
+
 }  // namespace internal
 }  // namespace admob
 }  // namespace firebase

admob/src/android/banner_view_internal_android.h

@@ -78,6 +78,9 @@ class BannerViewInternalAndroid : public BannerViewInternal {
   // the future callback pointer.
   Future<void> InvokeNullary(BannerViewFn fn,
                              banner_view_helper::Method method);
+
+  // Cleans up any C++ side data before invoking the Android SDK to do the same.
+  void DestroyInternalData();
 };
 
 }  // namespace internal

admob/src/common/banner_view_internal.h

@@ -35,6 +35,7 @@ enum BannerViewFn {
   kBannerViewFnPause,
   kBannerViewFnResume,
   kBannerViewFnDestroy,
+  kBannerViewFnDestroyOnDelete,
   kBannerViewFnMoveTo,
   kBannerViewFnCount
 };