compile failed with a break in a RT module task

Hi, everyone
I am trying to work with the RT task in module now in LinuxCNC with a kernel version of 3.4.9 and a RTAI version of 3.9.
I use the source in /usr/rtai/testsuite/kern/latency as a start point, and add an break in the while loop. Then the make process warned that: "__fixunsdfsi"  undefined!, and the insert of the module failed with the message on terminal window: Error: could not insert module *.ko: Unknown symbol in module
and an message showed with dmesg: Unknown symbol __fixunsdfsi (err 0)

Some results by google says that this problem may be caused by the float point computation, but I only added a break in the loop. 

Have you ever met the similar problem before? 
Or can you give me some suggestion?
3Q~

                                                                      yours  C.P.
                                                                    2016-10-20

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