Stack behavior in Solaris threads is generally the same as that in pthreads. For more information about stack setup and operation, see About Stacks.
You can get the absolute minimum on stack size by calling thr_min_stack(), which returns the amount of stack space required for a thread that executes a null procedure. Useful threads need more than this, so be very careful when reducing the stack size.
You can specify a custom stack in two ways. The first is to supply a NULL for the stack location, thereby asking the runtime library to allocate the space for the stack, but to supply the desired size in the stacksize parameter to thr_create().
The other approach is to take overall aspects of stack management and supply a pointer to the stack to thr_create(). This means that you are responsible not only for stack allocation but also for stack deallocation—when the thread terminates, you must arrange for the disposal of its stack.