user memory accessl in the pthread

["Anmo Kim" <kanmo@cisl.snu.ac.kr>]

We want to use some system functions in the pthread, such as sys_open(), sys_read(), sys_close(), etc.
As many developer knew, those functions require user memory segment for the passing of their arguments.
We can use those functions  only after including <uaccess.h> 
and replacing the current segment from  the kernel level to the user level by using get_ds(), set_ds(), etc.

This mechanism operates well without pthread in the RT-Linux module.
i.e. We can use sys_open(), sys_read(), etc. in init_module() without any problem.

However, Those system functions can't be used with pthread.
When we changed the segment in the pthread for those system functions, we met system halt always.

I guess that current pthread code of RT-Linux was written 
without any consideration of the functions in the <uaccess.h>.

Tell me
Why user segment access is impossible in the pthread.
How I can get user segment in the pthread.
Where I can obtain helpful documents for this problem.

Thank you.

Anmo Kim.
Control Information Systems Lab.
Seoul National Univ., Korea(ROK)