Move BinderProxy serialization into Java.
The BinderProxy class is not thread-safe, and all calls into
it were serialized by holding gProxyLock from JNI code. More
recently, we've been wanting to access BinderProxy from Java
code directly, and having the lock in native complicated things.
This change removes the lock in native code and adds it in the
Java layer. A benefit of this change is that it reduces the
scope of where a lock is held. On the flip side, we no longer
have a cached BinderProxyNativeData object lying around. This
means we now allocate/free a BinderProxyNativeData even if we
already have a Java object lying around for the native object,
which can happen quite frequently. But we deem the impact of
this to be acceptable.
Bug: 109888955
Test: sailfish builds, boots, proxy warnings still show
Change-Id: If2f4dbe5486ec7af0ef8ea42d24ac3a4330cc05a
diff --git a/core/jni/android_util_Binder.cpp b/core/jni/android_util_Binder.cpp
index c3ba9ba..7e2bad2 100644
--- a/core/jni/android_util_Binder.cpp
+++ b/core/jni/android_util_Binder.cpp
@@ -155,9 +155,8 @@
static constexpr int32_t PROXY_WARN_INTERVAL = 5000;
static constexpr uint32_t GC_INTERVAL = 1000;
-// Protected by gProxyLock. We warn if this gets too large.
-static int32_t gNumProxies = 0;
-static int32_t gProxiesWarned = 0;
+static std::atomic<uint32_t> gNumProxies(0);
+static std::atomic<uint32_t> gProxiesWarned(0);
// Number of GlobalRefs held by JavaBBinders.
static std::atomic<uint32_t> gNumLocalRefsCreated(0);
@@ -632,12 +631,6 @@
return (BinderProxyNativeData *) env->GetLongField(obj, gBinderProxyOffsets.mNativeData);
}
-static Mutex gProxyLock;
-
-// We may cache a single BinderProxyNativeData node to avoid repeat allocation.
-// All fields are null. Protected by gProxyLock.
-static BinderProxyNativeData *gNativeDataCache;
-
// If the argument is a JavaBBinder, return the Java object that was used to create it.
// Otherwise return a BinderProxy for the IBinder. If a previous call was passed the
// same IBinder, and the original BinderProxy is still alive, return the same BinderProxy.
@@ -652,36 +645,31 @@
return object;
}
- // For the rest of the function we will hold this lock, to serialize
- // looking/creation/destruction of Java proxies for native Binder proxies.
- AutoMutex _l(gProxyLock);
+ BinderProxyNativeData* nativeData = new BinderProxyNativeData();
+ nativeData->mOrgue = new DeathRecipientList;
+ nativeData->mObject = val;
- BinderProxyNativeData* nativeData = gNativeDataCache;
- if (nativeData == nullptr) {
- nativeData = new BinderProxyNativeData();
- }
- // gNativeDataCache is now logically empty.
jobject object = env->CallStaticObjectMethod(gBinderProxyOffsets.mClass,
gBinderProxyOffsets.mGetInstance, (jlong) nativeData, (jlong) val.get());
if (env->ExceptionCheck()) {
// In the exception case, getInstance still took ownership of nativeData.
- gNativeDataCache = nullptr;
return NULL;
}
BinderProxyNativeData* actualNativeData = getBPNativeData(env, object);
if (actualNativeData == nativeData) {
- // New BinderProxy; we still have exclusive access.
- nativeData->mOrgue = new DeathRecipientList;
- nativeData->mObject = val;
- gNativeDataCache = nullptr;
- ++gNumProxies;
- if (gNumProxies >= gProxiesWarned + PROXY_WARN_INTERVAL) {
- ALOGW("Unexpectedly many live BinderProxies: %d\n", gNumProxies);
- gProxiesWarned = gNumProxies;
+ // Created a new Proxy
+ uint32_t numProxies = gNumProxies.fetch_add(1, std::memory_order_relaxed);
+ uint32_t numLastWarned = gProxiesWarned.load(std::memory_order_relaxed);
+ if (numProxies >= numLastWarned + PROXY_WARN_INTERVAL) {
+ // Multiple threads can get here, make sure only one of them gets to
+ // update the warn counter.
+ if (gProxiesWarned.compare_exchange_strong(numLastWarned,
+ numLastWarned + PROXY_WARN_INTERVAL, std::memory_order_relaxed)) {
+ ALOGW("Unexpectedly many live BinderProxies: %d\n", numProxies);
+ }
}
} else {
- // nativeData wasn't used. Reuse it the next time.
- gNativeDataCache = nativeData;
+ delete nativeData;
}
return object;
@@ -959,8 +947,7 @@
jint android_os_Debug_getProxyObjectCount(JNIEnv* env, jobject clazz)
{
- AutoMutex _l(gProxyLock);
- return gNumProxies;
+ return gNumProxies.load();
}
jint android_os_Debug_getDeathObjectCount(JNIEnv* env, jobject clazz)
@@ -1008,8 +995,6 @@
{
JNIEnv *env = AndroidRuntime::getJNIEnv();
{
- // Calls into BinderProxy must be serialized
- AutoMutex _l(gProxyLock);
env->CallStaticObjectMethod(gBinderProxyOffsets.mClass,
gBinderProxyOffsets.mDumpProxyDebugInfo);
}
@@ -1367,9 +1352,6 @@
static void BinderProxy_destroy(void* rawNativeData)
{
- // Don't race with construction/initialization
- AutoMutex _l(gProxyLock);
-
BinderProxyNativeData * nativeData = (BinderProxyNativeData *) rawNativeData;
LOGDEATH("Destroying BinderProxy: binder=%p drl=%p\n",
nativeData->mObject.get(), nativeData->mOrgue.get());