Where is this ParcelFileDescriptor Leak Occurring?

问题

I have implemented a BackupAgent following the guidelines for Data Backup. The code behaves as expected until StrictMode.VmPolicy is set to detect leaked closeable objects. After a backup is performed and GC occurs, CloseGuard reports a leaked ParcelFileDescriptor with this stack trace:

06-28 21:47:39.683  25072-25081/com.qbix.nub E/StrictMode﹕ A resource was acquired at attached stack trace but never released. See java.io.Closeable for information on avoiding resource leaks.
    java.lang.Throwable: Explicit termination method 'close' not called
            at dalvik.system.CloseGuard.open(CloseGuard.java:184)
            at android.os.ParcelFileDescriptor.<init>(ParcelFileDescriptor.java:179)
            at android.os.ParcelFileDescriptor$1.createFromParcel(ParcelFileDescriptor.java:905)
            at android.os.ParcelFileDescriptor$1.createFromParcel(ParcelFileDescriptor.java:897)
            at android.app.IBackupAgent$Stub.onTransact(IBackupAgent.java:64)
            at android.os.Binder.execTransact(Binder.java:404)
            at dalvik.system.NativeStart.run(Native Method)
06-28 21:47:39.683  25072-25081/com.qbix.nub W/System.err﹕ StrictMode VmPolicy violation with POLICY_DEATH; shutting down.
06-28 21:47:39.683  25072-25081/com.qbix.nub I/Process﹕ Sending signal. PID: 25072 SIG: 9

To confirm that I was not leaking the ParcelFileDescriptor in my BackupAgent, I stubbed onBackup() like this:

@Override
public void onBackup(ParcelFileDescriptor oldState, BackupDataOutput data, ParcelFileDescriptor newState) throws IOException {
    if (oldState != null) {
        oldState.close();
    }
    newState.close();
    return;
}

This change did not fix the leak.

These are the steps I use to reproduce the problem:

Modify app data to trigger a call to BackupManager.dataChanged()
Use adb shell bmgr run to force a backup operation
Initiate GC from Android Studio

I don't know enough about bound services to understand if the stack trace provides clues about whether the leak is in the system BackupService or is caused by an error in my code I am unable to see. The continued occurrence of the leak when running with the stubbed onBackup() suggests to me that the leak is in the service.

While researching this issue, I found these other issues posted in the last few months that included the same leak report in their logcats:

Resource leak in Android

Having problems With navigation Drawer in Android

Android - HTTP Get - Explicit Termination not called error. What am I missing?

Resolving java.lang.Throwable exception in an android

The logcat shown above is from a KitKat device. On another device running Lollipop, I think the same error is occurring. The app is killed but the logcat does not include the CloseGuard dump. Don't know what I need to do to see that.

来源：https://stackoverflow.com/questions/31108503/where-is-this-parcelfiledescriptor-leak-occurring

标签

android

android-backup-service

android-strictmode