Re: Issues using statprof (no samples taken)

[Boris Zbarsky <bzbarsky@MIT.EDU>]

Ludovic Courtès wrote:
> GDB supposedly shows all SIGPROFs that are raised, so if it shows only
> one, then something's wrong.

Sure.  The wrong thing is that profile-signal-handler is not called, so 
never resets the timer, so no more SIGPROFs.  Unless I'm misreading the 
code.

> Can you check the arguments passed to `setitimer(2)' to make sure it makes sense?

I can't check the values in the structs it's passed, unfortunately (no 
symbols here for guile or the libc).

> Perhaps you could also try
> increasing the sampling frequency, although that's arguably not
> required.

I'm sampling every 500us, so I doubt that's the issue.  The task I'm 
profiling takes 20 seconds.

> Another (remote) possibility could be that the Scheme-level handler is
> not called, even though the C handler in libguile is called, since
> Scheme-level signal handlers are actually asyncs (info "(guile)
> Asyncs").  You can try to force the execution of asyncs by adding a call
> like "(select '() '() '() 0)" (technically, it invokes `SCM_TICK', which
> runs asyncs).

Where would I add that?  For that matter, what's the C handler in 
libguile?  I should be able to breakpoint on that and see whether it's 
called, hopefully...

Note that I'm just using the statprof.scm from guile-lib

> One last thing would be to check whether `HAVE_SIGACTION' is defined in
> Guile's <config.h> on your platform, to see which version of
> `scm_sigaction_for_thread ()' is used.

Yes, HAVE_SIGACTION is defined (to 1).

-Boris