On Dienstag, 16. Mai 2017 16:38:29 CEST Namhyung Kim wrote:
> On Tue, May 16, 2017 at 10:59:51AM +0200, Milian Wolff wrote:
> > As the documentation for dwfl_frame_pc says, frames that
> > are no activation frames need to have their program counter
> > decremented by one to properly find the function of the caller.
> >
> > This fixes many cases where perf report currently attributes
> > the cost to the next line. I.e. I have code like this:
> >
> > ~~~~~~~~~~~~~~~
> >
> > #include <thread>
> > #include <chrono>
> >
> > using namespace std;
> >
> > int main()
> > {
> >
> > this_thread::sleep_for(chrono::milliseconds(1000));
> > this_thread::sleep_for(chrono::milliseconds(100));
> > this_thread::sleep_for(chrono::milliseconds(10));
> >
> > return 0;
> >
> > }
> >
> > ~~~~~~~~~~~~~~~
>
> It'd be nice if the test program has a signal frame for verification.
I have pretty much zero experience about signals. Would it be enough to add a
signal handler for, say, SIGUSR1 to my test application and then trigger a
sleep when that signal is delivered? If that should be enough, I'll write and
test it out.
<snip>
> > diff --git a/tools/perf/util/unwind-libunwind-local.c
> > b/tools/perf/util/unwind-libunwind-local.c index
> > f8455bed6e65..30ab26375c80 100644
> > --- a/tools/perf/util/unwind-libunwind-local.c
> > +++ b/tools/perf/util/unwind-libunwind-local.c
> > @@ -690,8 +690,22 @@ static int get_entries(struct unwind_info *ui,
> > unwind_entry_cb_t cb,>
> > if (ret)
> >
> > display_error(ret);
> >
> > + bool previous_frame_was_signal = false;
> >
> > while (!ret && (unw_step(&c) > 0) && i < max_stack) {
> >
> > unw_get_reg(&c, UNW_REG_IP, &ips[i]);
> >
> > +
> > + /*
> > + * Decrement the IP for any non-activation frames.
> > + * this is required to properly find the srcline
> > + * for caller frames.
> > + * See also the documentation for dwfl_frame_pc,
> > + * which this code tries to replicate.
> > + */
> > + bool frame_is_signal = unw_is_signal_frame(&c) > 0;
> > + if (!previous_frame_was_signal && !frame_is_signal)
> > + --ips[i];
> > + previous_frame_was_signal = frame_is_signal;
>
> Does it need to check previous frame too?
That's what dwfl_frame_pc does, if I'm not misunderstanding it's source code?
Bye
--
Milian Wolff | [email protected] | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts
smime.p7s
Description: S/MIME cryptographic signature
