-Xcheck:jni should check for threads making JNI calls made in critical regions.
A critical region for this purpose occurs when a thread has made one or
more calls to GetStringCritical or GetPrimitiveArrayCritical without yet
having made the matching Release call.

Violating this rule can cause deadlock.  Garbage collection may be blocked
in the critical region, and any attempt to allocate java objects in the
critical region might require garbage collectio in order to complete.