Question

I have uploaded my application on google play but users have reported the following exception

java.lang.RuntimeException: WakeLock under-locked C2DM_LIB. This exception occurs when I try to release the WakeLock. Can anyone tell what could be the problem.

Answer 1

I have traced same exception in new GCM Library too. Actually old C2DM Android library have same error, same crash, and Google hasn’t fixed it yet. As I can see by our statistics, about 0.1% of users experiencing this crash.

My investigations shows that problem is in incorrect releasing of network WakeLock in GCM library, when library tries to release WakeLock that holds nothing (internal lock counter becomes negative).

I was satisfied with simple solution – just catch this exception and do nothing, because we don’t need to do any extra job then our wakelock hold nothing.

In order to do this you need to import GCM library sources in your project, rather than already compiled .jar file. You can find GCM library sources under “$Android_SDK_Home$/extras/google/gcm/gcm-client/src” folder (you need to download it first using Android SDK Manager).

Next open GCMBaseIntentService class, find line

sWakeLock.release();

and surround it with try-catch.

It should look like this:

    synchronized (LOCK) {
        // sanity check for null as this is a public method
        if (sWakeLock != null) {
            Log.v(TAG, "Releasing wakelock");
            try {
                sWakeLock.release();
            } catch (Throwable th) {
                // ignoring this exception, probably wakeLock was already released
            }
        } else {
            // should never happen during normal workflow
            Log.e(TAG, "Wakelock reference is null");
        }
    }

UPDATE:
Alternativally, as suggested @fasti in his answer, you can use mWakeLock.isHeld() method to check if wakelock actually holding this lock.