io apic + tsc = slowdown (bugreport + possible fix)

[Frederic Krueger <spamalltheway@bigfoot.com>]

Hi,

just wanted to point out the patch I imported from an older version of 
the 2.6.x kernel (not done by me at all ;-)).
It's basically causing the system to a near zero slowdown after one hour 
of uptime. And the reason for it must be the io_apic irq0 handling with 
TSC enabled systems (seems to show up on ibm pre-built boxes more often 
than on others though).
Funnily pressing any keys _all the time_ works around for this for the 
time a key is pressed ;)

The bug report entry contains a patch for arch/i386/kernel/io_apic.c  
which fixed it for me.
Maybe this should make it into the cvs tree since it's a _really_ 
annoying bug, basically rendering the computer unusable if present.

The link to the bug report with more detailed information can be found here:
http://bugme.osdl.org/show_bug.cgi?id=2964

Thanks for checking and considering :-)

Bye,
Frederic