which Thread makes stop all the world - Gc logs

Question

I have found that gc logs without gc activites means that another activity that blocks the system.

1. How can find which thread can cause the stop all the world on the system

2. I have 8 CPU server. Why one thread is in a stuck (or in a loop), other threads cannot work simulteneously. They wait for the stuck Thread.

Regards Trustin

49024K->0K(49088K), 0.0134360 secs] 1143252K->1096715K(2170816K), 0.0136590 secs] [Times: user=0.08 sys=0.01, real=0.01 secs] Total time for which application threads were stopped: 0.0172190 seconds Application time: 9.3082360 seconds 2010-06-08T10:12:27.155-0500: 2015.285: [GC 2015.285: [ParNew Desired survivor size 32768 bytes, new threshold 0 (max 0) : 49024K->0K(49088K), 0.0163970 secs] 1145739K->1099201K(2170816K), 0.0165920 secs] [Times: user=0.07 sys=0.01, real=0.02 secs] Total time for which application threads were stopped: 0.0201840 seconds Application time: 5.4705750 seconds Total time for which application threads were stopped: 0.8505860 seconds Application time: 0.0012020 seconds Total time for which application threads were stopped: 0.8519010 seconds Application time: 0.0004510 seconds Total time for which application threads were stopped: 0.8508060 seconds Application time: 0.0007170 seconds