Why doesn't my GPU data sync with my CPU data? It's a strange problem. I don't kown how to solve it.

[xuexigua]

I try to print CPU data and GPU data in my loss layer Forward_gpu() function like this:
LOG(INFO)<<bottom[0]->cpu_data()[0];
LOG(INFO)<<bottom[0]->gpu_data()[0];
Finally, the CPU data was successfully printed, but the CPU data wasn't.
And SSD-caffe can run successfully.
This is my currnet server information:
Ubuntu 14.04
CUDA8.0
cudnn6.0

The same code executed successfully on my other computer.