__builtin_return_address()

[Der Herr Hofrat]

Hi !

 I wanted to locate a delay in a Linux kernel module and to do this added a few

 addr1=__builtin_return_address(0);
 addr2=__builtin_return_address(1);
 addr3=__builtin_return_address(2);
 ...

 to the code if a cirtain delay was reached - the problem was that it 
 segfaults if I try to grab __builtin_return_address(2) which I don't 
 understand why , or maby more precisely, how can I check how deep I 
 can backtrace calls ?

thx !
hofrat