commit 402c8676685ae16277ef556cf7c5265ae2184c6b
author Martijn Coenen <maco@google.com> Mon Feb 03 10:01:36 2020 +0100
committer Martijn Coenen <maco@google.com> Wed Feb 05 14:02:51 2020 +0000
tree ed0fb467cca9db4bd3975e1558367d2607a0d01f
parent fde696396db83593dfb4b929faf9510141b91f46

Fix defaultServiceManager() locking and retry loop.

Use a static instead of double-checked locking.

Bug: 142838845
Test: builds
Change-Id: I0b42539cae70a70c6a23798c27f6b088bb5d3b40

libs/binder/IServiceManager.cpp

diff --git a/libs/binder/IServiceManager.cpp b/libs/binder/IServiceManager.cpp
index 328653a..9888b59 100644
--- a/libs/binder/IServiceManager.cpp
+++ b/libs/binder/IServiceManager.cpp
@@ -85,31 +85,36 @@
     sp<AidlServiceManager> mTheRealServiceManager;
 };
 
-static Mutex gDefaultServiceManagerLock;
+static std::once_flag gSmOnce;
 static sp<IServiceManager> gDefaultServiceManager;
 
 sp<IServiceManager> defaultServiceManager()
 {
-
-    if (gDefaultServiceManager != nullptr) return gDefaultServiceManager;
-
-    {
-        AutoMutex _l(gDefaultServiceManagerLock);
-        while (gDefaultServiceManager == nullptr) {
-            gDefaultServiceManager = new ServiceManagerShim(
-                interface_cast<AidlServiceManager>(
-                    ProcessState::self()->getContextObject(nullptr)));
-            if (gDefaultServiceManager == nullptr)
+    std::call_once(gSmOnce, []() {
+        sp<AidlServiceManager> sm = nullptr;
+        while (sm == nullptr) {
+            sm = interface_cast<AidlServiceManager>(ProcessState::self()->getContextObject(nullptr));
+            if (sm == nullptr) {
                 sleep(1);
+            }
         }
-    }
+
+        gDefaultServiceManager = new ServiceManagerShim(sm);
+    });
 
     return gDefaultServiceManager;
 }
 
 void setDefaultServiceManager(const sp<IServiceManager>& sm) {
-  AutoMutex _l(gDefaultServiceManagerLock);
-  gDefaultServiceManager = sm;
+    bool called = false;
+    std::call_once(gSmOnce, [&]() {
+        gDefaultServiceManager = sm;
+        called = true;
+    });
+
+    if (!called) {
+        LOG_ALWAYS_FATAL("setDefaultServiceManager() called after defaultServiceManager().");
+    }
 }
 
 #if !defined(__ANDROID_VNDK__) && defined(__ANDROID__)