libfakeservicemanager: no hold lock in clear

destructors may reference servicemanager, and so
if objects are destroyed by libfakeservicemanager
clear, this was causing a recursive lock take.

Fix this the standard way, by using the lock to
copy out references, and then clear them when
its okay to talk to servicemanager again.

Bug: N/A
Test: w/ fuzzers
Change-Id: I4795ff6e042324e6ffe76f6c915c1328d3eee94f

libs/fakeservicemanager/FakeServiceManager.cpp

diff --git a/libs/fakeservicemanager/FakeServiceManager.cpp b/libs/fakeservicemanager/FakeServiceManager.cpp
index ae242f3..08f30de 100644
--- a/libs/fakeservicemanager/FakeServiceManager.cpp
+++ b/libs/fakeservicemanager/FakeServiceManager.cpp
@@ -122,9 +122,19 @@
 }
 
 void FakeServiceManager::clear() {
-    std::lock_guard<std::mutex> l(mMutex);
+    std::map<String16, sp<IBinder>> backup;
 
-    mNameToService.clear();
+    {
+      std::lock_guard<std::mutex> l(mMutex);
+      backup = mNameToService;
+      mNameToService.clear();
+    }
+
+    // destructors may access FSM, so avoid recursive lock
+    backup.clear(); // explicit
+
+    // TODO: destructors may have added more services here - may want
+    // to check this or abort
 }
 }  // namespace android
 
@@ -147,4 +157,4 @@
     LOG_ALWAYS_FATAL_IF(gFakeServiceManager == nullptr, "Fake Service Manager is not available. Forgot to call setupFakeServiceManager?");
     gFakeServiceManager->clear();
 }
-} //extern "C"
\ No newline at end of file
+} //extern "C"