Who can help with the strange linux multi-thread programming errors ??

Who can help with the strange linux multi-thread programming errors ?? -- Linux general technology-Linux technology and application information. For details, refer to the following section. I recently wrote a simple server program under ubuntu10.10, but there was a strange error. I have not found the cause so far. The details are as follows:

The main thread listens to port data and adopts the select method. The next thread accepts commands to control the data output of the serial port. So I thought of using the structure as a global variable, share data between threads (I don't know how to handle data sharing, which is usually used in most cases ). However, a problem occurs in the sub-thread (the main thread and the sub-thread are not in the same file). The prompt is as follows:
Error: request for member 'ctrollkind' in something not a structure or union
Error: request for member 'ctrollnum' in something not a structure or union
Error: request for member 'ctrolltype' in something not a structure or union

The structure is declared in the header file of the main thread and defined in the main thread. The Code is as follows:
Typedef struct ctroll ctr;
Struct CTROLL
{
Int ctrollKind;/* ctroll the motor or led */
Int ctrollType;/* the ctroll kind turn on or turn off */
Int ctrollNum;/* the number of the led */
};

The structure is defined in the main thread. The Code is as follows:
CTR ctroll;

The time code used by the sub-thread is as follows:
Extern ctroll;
...
Ctr_kind = ctroll. ctrollKind;
Num = ctroll. ctrollNum;
Action = ctroll. ctrollType;

The above problem occurs during compilation. The strange thing is that I used the same method and shared another variable without prompting similar errors.
After checking for a long time, I also found a lot of relevant information on the Internet, but I was confused these days. Who can help.