Re: emacs crash on SMP notebook only

[Joost Helberg]

Richard,

>>>>> "Richard" == Richard M Stallman <address@hidden> writes:
 > Date: Sat, 26 Nov 2005 19:31:52 -0500

 >     I've investigated further and came to the conclusion that this is
 >     related to using gcc-4.0.2.
 >     Using a gcc-3.4 compiled GNU Emacs works fine now.

 > That is disturbing.  It could be a GCC bug.

 >     I'm using GNU/Linux of the Debian sort on Intel 4 3.6GHz with
 >     hyperthreading enabled. Using NO hyperthreading (a kernel option) with
 >     gcc-4.0.2 compiled emacs shows no crashes.

 > I am not sure what hyperthreading is.  Does it alter the execution of
 > machine code?

It presents the kernel with 2 CPU's. The CPU can then use wait-states
etc. for time-sharing on a CPU-level.
Intel claims a 30% performance gain and better `interactive'
performance. 

 > Please confirm the meaning of these statements.  Are you saying that
 > the same Emacs executable (made with GCC 4) crashes with
 > hyperthreading but does not crash when run without hyperthreading?

I was saying exactly that.

 > Does the Emacs executable made with GCC 3.4 run correctly both
 > with and without hyperthreading?
Now I know that the GCC 3.4 compiled Emacs crashes too, but not as
often. But there is less alarming news:

  Emacs-22 (from CVS) works OK (i.e. with hyperthreading, GCC 4).

  Emacs-21.4 as bundled with my OS but recompiled, crashes often with
                hyperthreading and GCC 4, crashed twice with GCC 3.4.

  Emacs-21.4 as deliverd by the FSF works fine using GCC 4 or
                GCC 3.4.

It looks as if the problem is either gcc or the patches from Debian or
Ubuntu. We can safely assume that gcc deserves more credits than
Debian and Ubuntu together.

I'm currently checking out the patches from Debian and Ubuntu, as I'm
pretty sure these make the crashes appear.

I'm sorry for any hassle I caused, as it looks like the problem sits
in people modifying code for no reason whatsoever.

I'll look further into the problem in order to complete feedback to
the Debian people, I feel a but reluctant though as no good can come
from the way their packaging works.

 > I think that is what you are saying, but let's make sure there is no
 > misunderstanding.

There is a clearer picture now which is a lot less disturbing.

 >     Can I help narrowing this thing down to a gcc or emacs issue?

 > The way to investigate further is to compile some of the files with
 > each compiler, and see if it crashes.  That way you can determine
 > which file has the problem.

 > Would you like to do that?

I will try to pin down the problem by looking further and suspecting
both GCC and the Debian/Ubuntu patches.

Regards,

Joost Helberg

-- 
Joost Helberg
Snow B.V.        http://snow.nl Tel 0418-653333 Fax 0418-653666
Voorzitter VOSN  http://www.vosn.nl Tel 0418-653336 Fax 0418-653666