Mark common android.os.Parcel methods as FastNative

Mark the marshaling functions for non-primitive parameters as being
@FastNative: they're all expected to complete quickly.

According to the table in CriticalNative.java, the difference between
a regular JNI call and a FastNative call is about 80ns, so this change
should shave about 160ns per non-primitive parameter off the latency
of a binder transaction. The actual savings will be greater as we also
use these Parcel methods to marshal and unmarshal complex objects like
PackageInfo sent as objects over Binder.

Bug: 142271139
Test: boots
Change-Id: I85c3ee8498640193b9c0777c8c5e7eb349c7b23c

core/java/android/os/Parcel.java

@@ -305,8 +305,11 @@ public final class Parcel {
     private static native void nativeWriteFloat(long nativePtr, float val);
     @FastNative
     private static native void nativeWriteDouble(long nativePtr, double val);
+    @FastNative
     static native void nativeWriteString(long nativePtr, String val);
+    @FastNative
     private static native void nativeWriteStrongBinder(long nativePtr, IBinder val);
+    @FastNative
     private static native long nativeWriteFileDescriptor(long nativePtr, FileDescriptor val);
 
     private static native byte[] nativeCreateByteArray(long nativePtr);
@@ -320,8 +323,11 @@ public final class Parcel {
     private static native float nativeReadFloat(long nativePtr);
     @CriticalNative
     private static native double nativeReadDouble(long nativePtr);
+    @FastNative
     static native String nativeReadString(long nativePtr);
+    @FastNative
     private static native IBinder nativeReadStrongBinder(long nativePtr);
+    @FastNative
     private static native FileDescriptor nativeReadFileDescriptor(long nativePtr);
 
     private static native long nativeCreate();

core/jni/android_os_Parcel.cpp

@@ -721,8 +721,11 @@ static const JNINativeMethod gParcelMethods[] = {
     {"nativeWriteFloat",          "(JF)V", (void*)android_os_Parcel_writeFloat},
     // @FastNative
     {"nativeWriteDouble",         "(JD)V", (void*)android_os_Parcel_writeDouble},
+    // @FastNative
     {"nativeWriteString",         "(JLjava/lang/String;)V", (void*)android_os_Parcel_writeString},
+    // @FastNative
     {"nativeWriteStrongBinder",   "(JLandroid/os/IBinder;)V", (void*)android_os_Parcel_writeStrongBinder},
+    // @FastNative
     {"nativeWriteFileDescriptor", "(JLjava/io/FileDescriptor;)J", (void*)android_os_Parcel_writeFileDescriptor},
 
     {"nativeCreateByteArray",     "(J)[B", (void*)android_os_Parcel_createByteArray},
@@ -736,8 +739,11 @@ static const JNINativeMethod gParcelMethods[] = {
     {"nativeReadFloat",           "(J)F", (void*)android_os_Parcel_readFloat},
     // @CriticalNative
     {"nativeReadDouble",          "(J)D", (void*)android_os_Parcel_readDouble},
+    // @FastNative
     {"nativeReadString",          "(J)Ljava/lang/String;", (void*)android_os_Parcel_readString},
+    // @FastNative
     {"nativeReadStrongBinder",    "(J)Landroid/os/IBinder;", (void*)android_os_Parcel_readStrongBinder},
+    // @FastNative
     {"nativeReadFileDescriptor",  "(J)Ljava/io/FileDescriptor;", (void*)android_os_Parcel_readFileDescriptor},
 
     {"nativeCreate",              "()J", (void*)android_os_Parcel_create},

core/jni/android_util_Binder.cpp

@@ -697,6 +697,9 @@ BinderProxyNativeData* getBPNativeData(JNIEnv* env, jobject obj) {
 // same IBinder, and the original BinderProxy is still alive, return the same BinderProxy.
 jobject javaObjectForIBinder(JNIEnv* env, const sp<IBinder>& val)
 {
+    // N.B. This function is called from a @FastNative JNI method, so don't take locks around
+    // calls to Java code or block the calling thread for a long time for any reason.
+
     if (val == NULL) return NULL;
 
     if (val->checkSubclass(&gBinderOffsets)) {