how to store static data in a multi-thread program?

["Andrew Makhorin" <mao@mai2.rcnet.ru>]

Hi,

I've got a multi-thread program (in C) running under Debian/GNU Linux.
And I need to store a pointer somewhere in a system place related to an
particular thread in order to pass it to other routines running in the
same thread. In other words I need to pass a pointer within a thread as
if it would be declared as extern (i.e. not as a formal parameter), but
in a thread safe manner. Could anyone please tell me how to do that?

Thank you,

Andrew Makhorin