is JNI in cocos2d-x thread safe?

my cocos version: 2.1.3
I wana put audio,file operation into non-main threads, but i got a “Failed to get the environment using GetEnv()” error.

I found JNI tips here : http://developer.android.com/training/articles/perf-jni.html
it means I could discover JNIEnv.

how can i do? thanks for any suggestion.