user mode backtrace

[David Boreham]

>
>
>We don't yet have a good answer to user-space stuff in general.  We
>may adopt a mixture of two approaches: one where the compiled
>systemtap probes get some extract of backtrace-enabling unwind
>information for selected user-space programs and libraries (so the
>backtrace processing can be done instantly right there); and another
>one where the probe may snapshot only an approximation (say a vector
>of probable PCs from the thread's stack frame), and rely on a
>user-space helper to correct/complete it for output later, off-line.
>  
>
Given the choice I'd prefer the latter because it'd be less intrusive.