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Date: Fri, 15 Mar 2002 13:56:27 -0800
From: Dan Kegel <dank@ixiacom.com>
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To: Jakub Jelinek <jakub@redhat.com>
CC: Dan Kegel <dkegel@ixiacom.com>, Ulrich Drepper <drepper@redhat.com>,
        darkeye@tyrell.hu, libc-gnats@gnu.org, gnats-admin@cygnus.com,
        sam@zoy.org, Xavier Leroy <Xavier.Leroy@inria.fr>,
        linux-kernel@vger.kernel.org, babt@us.ibm.com
Subject: Re: libc/1427: gprof does not profile threads <synopsis of the problem 
 (one li\ne)>
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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
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