please help me about __builtin_return_address

[<shin.anzai@xxxxxxxxxxxxx>]

Hello,

I got following warning message using gcc-3.4.6-3 on IA64 server;

include/linux/smp_lock.h: In function `init':
include/linux/smp_lock.h:60: warning: unsupported arg to `__builtin_return_address'


The lock_kernel function referred by init is as follows;

static inline void lock_kernel(void)
{
        int depth = current->lock_depth+1;
        if (likely(!depth)) {
                get_kernel_lock();
                kernel_lock_trace_buffer[kernel_lock_trace_index%16] = current;
                kernel_lock_addr[kernel_lock_trace_index++%16]
                    = __builtin_return_address(2);
        }
        current->lock_depth = depth;
}

Could you let me know how can I use __builtin_return_address?
Or, is there any alternative to get caller' address of lock_kernel function or caller's caller? 

Thank you,

Shin Anzai