ThreadState during GC
I'm investigating odd CPU spikes we're experiencing in our J2EE app running on Glassfish. When it happens, I notice that there are full GC's running back to back to back and the server becomes non-responsive. I've also been taking jstack dumps during these periods and noticed that most worker threads at this point have the ThreadState: BLOCKED (on object monitor). So, my question is:
Is it normal to see many threads in ThreadState: BLOCKED (on object monitor) during a full GC? If not, is there a usual or common ThreadState during full GCs?