diagnosing emacs hangs

diagnosing emacs hangs

[Matt Price]

Hi all,

I'm now using emacs for almost everything and of course that's great,
except that it is essentially a single-threaded OS that currently
HANGS with some frequency (100% CPU usgte that will continue for hours
if you let it go.  I think this probably has something to do with
wanderlust or possibly org-mode (and/or misconfigurations i've made to
both of these); but at present i cna't be sure since i have no idea
how to diagnose these hangs.  Can someone give me some general
directions on how to proceed with the diagnosis, and if you have them,
some pointers on how you fixed a similar problem that you used to
have?  Right now it's very frustrating -- I find myself losing
substantial amounts of work when I kill emacs & maybe more
importantly, i'm constantly losing my train of thought.

This is all under Ubuntu Lucid with emacs-snapshot 20090909,
wanderlust=wl-beta 2.15.9+0.20100303, org-mode 6.34c (some of htese
are debian sid packages).

Thanks much in advance,

matt

Re: diagnosing emacs hangs

[Qiang Guo]

Hi Matt

I run into the same problem some time ago. I guess it's
probably the cause of wanderlust. After some idle time,
emacs will hang unless I restart the program. Try to set
'elmo-network-session-idle-timeout' variable to a reasonable
value (thanks to somebody on wanderlust's mailinglist :-)).

Hope it helps

Qiang

Re: diagnosing emacs hangs

[Ian Barton]

On 22/06/10 02:18, Matt Price wrote:
> Hi all,
>
> I'm now using emacs for almost everything and of course that's great,
> except that it is essentially a single-threaded OS that currently
> HANGS with some frequency (100% CPU usgte that will continue for hours
> if you let it go.  I think this probably has something to do with
> wanderlust or possibly org-mode (and/or misconfigurations i've made to
> both of these); but at present i cna't be sure since i have no idea
> how to diagnose these hangs.  Can someone give me some general
> directions on how to proceed with the diagnosis, and if you have them,
> some pointers on how you fixed a similar problem that you used to
> have?  Right now it's very frustrating -- I find myself losing
> substantial amounts of work when I kill emacs&  maybe more
> importantly, i'm constantly losing my train of thought.
>
> This is all under Ubuntu Lucid with emacs-snapshot 20090909,
> wanderlust=wl-beta 2.15.9+0.20100303, org-mode 6.34c (some of htese
> are debian sid packages).
>
Have you tried starting Emacs from a terminal? That might give you some 
better idea of the error.

Ian.

Re: diagnosing emacs hangs

[Tassilo Horn]

Hi!

Usually, you debug hangs by doing `M-x toggle-debug-on-quit' and hitting
`C-g' when it hangs.  Then you'll get a backtrace, which should point
you to the infinte loop or something like that.

Bye,
Tassilo

Re: diagnosing emacs hangs

[Nick Dokos]

Matt Price <moptop99@gmail.com> wrote:


> I'm now using emacs for almost everything and of course that's great,
> except that it is essentially a single-threaded OS that currently
> HANGS with some frequency (100% CPU usgte that will continue for hours
> if you let it go.  I think this probably has something to do with
> wanderlust or possibly org-mode (and/or misconfigurations i've made to
> both of these); but at present i cna't be sure since i have no idea
> how to diagnose these hangs.  Can someone give me some general
> directions on how to proceed with the diagnosis, and if you have them,
> some pointers on how you fixed a similar problem that you used to
> have?  Right now it's very frustrating -- I find myself losing
> substantial amounts of work when I kill emacs & maybe more
> importantly, i'm constantly losing my train of thought.
> 
> This is all under Ubuntu Lucid with emacs-snapshot 20090909,
> wanderlust=wl-beta 2.15.9+0.20100303, org-mode 6.34c (some of htese
> are debian sid packages).
> 

I assume only emacs is stuck, so you can open an xterm: what does ``ps
awlx | grep emacs'' say?  In particular, the state and the wchan are of
interest: normally, it should be in S state and waiting on select: idle
and waiting for input. If it's persistently in D state, it's stuck
somewhere in the kernel - the wchan gives an idea where. Do it a few times
to make sure that things are not changing.

The next step is to do ``strace -p<emacs_pid>'' to see whether it's going
in and out of the kernel (perhaps in an infinite loop).

If it is *not* going into the kernel, but accumulates CPU runtime (check
the ps awlx output a few times), then it's stuck in a loop in user
space. Attaching to it with ``gdb -p<emacs_pid>'' and getting a
backtrace should give an idea of where it's stuck. But if the loop is in
lisp code, the backtrace is not going to tell you where: it'll just be
in eval. If that's the case, then bisecting through your .emacs setup is
probably the best idea (maybe start by commenting out the org/wanderlust
stuff, particularly if you started getting these problems recently,
after making changes to their configuration.)

It's always a good idea to do these things with a working emacs first, so
that you learn what "normal" looks like. Then you have a better idea
of what's wrong when you try them on the stuck emacs.

This only scratches the surface but...

HTH,
Nick