Subject: FVWM: Weird fvwm crash bug

From: Nix <[email-masked]>
Date: 03 Nov 2001 13:21:13 +0000

With fvwm-2.4.1 and above, I've been experiencing really weird X
crashes. fvwm works fine, until I switch virtual consoles away from X
and back again. When using any window manager but fvwm-2.4.x, nothing
bad happens; but if fvwm-2.4.x is running in the X session[1], every X
client that was being managed by fvwm at the time of the switch freezes
solid. fvwm thinks it's still there (so you can manipulate the --- now
forever unrepainted --- windows), and the process is still there, but
it's blocked in select() forevermore.

I'm using XFree86-4.1.0 (from CVS at XFree86) on an i586-pc-linux-gnu
box with glibc-2.2.4 and the mga driver.

I'm not sure if this is really a fvwm bug, but fvwm is implicated
(somehow); if it's not a fvwm bug it's an XFree86 bug triggered by
fvwm-2.4.x. To be honest, I'm not even sure where to start searching for
the bug; nothing's looping and eating CPU or I could hit it with gprof,
nothing dumps core, and I'd rather eat my own intestines than try to
debug a running X server. Everything just, well, stops working.

(This probably started happening somewhere in the 2.3.x range, but I
jumped straight from 2.2.5 to 2.4.1. It still happens with 2.4.3.)

I'm stumped. Anyone else got any clues?

[1] I'm not sure if the session being switched away from or the one
    being switched to crashes.

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---

From: Marcus Lundblad <[email-masked]>
Date: Sun, 4 Nov 2001 01:01:39 +0100 (CET)

> jumped straight from 2.2.5 to 2.4.1. It still happens with 2.4.3.)

I've also experianced similar things. Sometimes everything hangs when
switchning VC. And it happens that my X-Server crashes when trying to log
out from fvwm2.

fvwm2 2.4.3 i686-pc-linux-gnu kernel 2.4.2-2, Xfree 4.0.3-5

I thought maybe it was a hardware problem, perhaps it wasn't...

//Marcus

---

From: Nix <[email-masked]>
Date: 04 Nov 2001 13:45:44 +0000

> fvwm2 2.4.3 i686-pc-linux-gnu kernel 2.4.2-2, Xfree 4.0.3-5

Well, it's nice to know I'm not on drugs, and that whatever it is it
isn't remotely XFree86-version or kernel-version dependent. :)

> I thought maybe it was a hardware problem, perhaps it wasn't...

Doesn't look like it. Test it; stick something in your X startup files
so you get an xterm before the wm starts and when you exit it, the wm
starts up; you'll find you can switch VCs with that xterm running with
impunity. But when fvwm starts, switching VCs is the kiss of death :(

---

From: Dominik Vogt <[email-masked]>
Date: Mon, 5 Nov 2001 11:39:11 +0100

> box with glibc-2.2.4 and the mga driver.

I had similar problems with XFree 4.0.x and the mga driver (G200).
XFree sometimes just exited or froze when switching between VC and
X - or worse: between two X servers.  But now that you mention it:
the problem seems to have gone away with my new machine
(GeForce2), but maybe I didn't test this enough yet.  This never
happened with XFree 3.3.x.  I really don't know what to do about
that.

> I'm stumped. Anyone else got any clues?

You could try using the svga driver instead.  Don't ask me how you
do this with XFree 4, though.

Bye

Dominik ^_^  ^_^

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---

From: Marcus Lundblad <[email-masked]>
Date: Mon, 5 Nov 2001 16:58:16 +0100 (CET)

> I had similar problems with XFree 4.0.x and the mga driver (G200).

I have a G200, so this seems it could be common.
Nix, what kind of card do you have?

I don't know if this is related, but in one of our departments the
standard setup uses fvwm2 2.0.46 on Solaris, and sometimes when logging
out (only on SunRay terminals) the X-server hangs (leaving a gray screen).
"Gray screen of death (GSOD)"... *lol*)

---

From: Dan Espen <[email-masked]>
Date: Tue, 06 Nov 2001 08:55:14 -0500

> impunity. But when fvwm starts, switching VCs is the kiss of death :(

A while back I had to debug a VC hanging problem with the S3 Savage4
card.  I'm slightly familiar with what goes on when the VC is
switched.

I don't see how FVWM can be to blame.  FVWM might be doing something
thats triggering the problem, like using a memory location on the
card or a feature that the Xterm or some other window manager
might not be using, but I think the problem is in the VC logic.

It was in my case.

If you can log into the machine while its hung, and attach dbx
to the xserver, that might point to the problem.  It would have
in my case, except that I couldn't log in from anywhere else,
and had to debug the problem with lots of printfs and flushes.

-- 
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