Re: libc/1427: gprof does not profile threads <synopsis of the problem

[Dan Kegel]

Jakub Jelinek wrote:
> 
> On Wed, Mar 13, 2002 at 04:19:02PM -0800, Dan Kegel wrote:
> > Ulrich Drepper wrote:
> > >
> > > On Wed, 2002-03-13 at 15:17, Dan Kegel wrote:
> > >
> > > > So let's break the logjam and fix glibc's linuxthreads' pthread_create
> > > > to [support profiling multithreaded programs]
> > >
> > > I will add nothing like this.  The implementation is broken enough and
> > > any addition just makes it worse.  If you patch your own code you'll get
> > > what you want at your own risk.
> >
> > OK.  What's the right way to fix this, then?
> 
> Surely don't use timer for profiling.
> Have the compiler generate profiling calls both at function entry and exit
> and use rdtsc/whatever other register your machine has (or even better
> profiling registers) to note time of that function being entered/left.

That's a different style of profiling.  There is a fellow
working on that (see http://sourceforge.net/projects/fnccheck )
but there's value in the gprof-style of profiling as well.
(For instance, I suspect it's lower overhead.)

I think it's reasonable for us to get gprof working; it's
a useful part of classic Unix, and the fix looks easy.

Ulrich, do you at least agree that it would be desirable for
gprof to work properly on multithreaded programs?

- Dan