Question on checking the stack

[Frank Ch. Eigler]

Bryce <philip.copeland@oracle.com> writes:

> [...]
> >>probe kernel.function("generic_make_request") {
> >>    if (stack(1) == "submit_bio" ) { // where stack(1) was the last
> >>routine  and stack(2) was 2nd last etc
> >>         do_test/display
> >>    }
> >>}
> >>[...]

> *nod* Just Sebastiaens hack has the unfortunate problem of needing
> to know in advance what all the exit addresses from a routine and
> combing the stack looking for a string match is probably rather slow
> if it happens often enough.

If one is stuck with the general approach of PC testing at the callee,
then one could micro-optimize the lookup a little more.  For example,
one could return a numeric PC value for "stack(1)", like GCC's
__builtin_return_address(1).  Such numbers would need to be converted
to symbol strings only once, since a yes/no judgement could be
memoized.

- FChE