lockups with kernel-2.17-1.2187_FC5

[George Avrunin]

I have a machine running FC5, fully updated.  With the new kernel and
glibc, I rebooted this morning.  Since then, I am getting reproducible
lockups.

The machine is my home desktop.  I can cause the lockup by doing 
   ssh -Y host
where host is either my laptop on the same LAN or my office
workstation connecting through a cable modem, and then running any
program that displays through the X server.  For instance, xemacs,
xpdf, evince, ooffice.  (I seem to get the same results ssh'ing to,
for instance, a machine running FC4, too, but I haven't checked as
thoroughly.)  The home desktop, which is an old Dell Precision 350,
then locks up immediately.  The cursor disappears from the screen, the
machine doesn't respond to the mouse or keyboard, and it isn't
accessible in any way over the network.  I have to use the power
button to shutdown.  I haven't seen anything in /var/log/messages at
the times the lockup occurs.  The laptop is running the same 8187
kernel, and the office machine is running FC5 but still with the 2174
kernel.  (The office machine is another Dell Precision workstation of
slightly different vintage.  When I go in Monday I will try rebooting
to the 8187 kernel to see if it shows the same behavior; I don't want
to try that remotely.)

Everything seems to work fine with the 2174 kernel.  The machine has a
Radeon R100 video card and an Intel Gigabit ethernet card (that uses
the e1000 driver).

I do have tcp_window_scaling set to 0 because the filtering bridge at
work has problems with window scaling, but I've seen the same lockups
at home with tcp_window_scaling set to 1.  (And the problems with the
bridge only lock up the particular tcp connection, not the whole
machine.)  

I'd appreciate any suggestions about how to track this down.
Meanwhile, I've reverted to using the 2174 kernel.

  George