Strange error message during kernel execution: "No kernel updates in a while..."

Hi,I also meet this problem.I used the board of DE4 530.I guess the reason of the error is that some kernels have been hung because of global mem synchronization. For some reasons the code can make the global mem synchronized, but I use the command of "barrier(CLK_GLOBAL_MEM_FENCE)" .So the kernels is stopped and blocking. The host is still waiting for the kernels.After I removed "barrier(CLK_GLOBAL_MEM_FENCE)" in my code,this error disappeared. Hope this can help you more or less.