Red Hat Bugzilla – Bug 184583
Kernel should export number and state of local APICs
Last modified: 2007-11-30 17:07:23 EST
Description of problem:
Userland (anaconda) needs to know how many CPUs are in a system, without concern
for the current CONFIG_NCPUS or "maxcpus=" setting. Apparently scanning this
from userland causes serious instability on some systems.
The kernel scans ACPI for this info during boot, but doesn't directly expose the
data to userland. So if the kernel could report how many local APICs there are
as well as which are enabled and disabled, regardless of the current "maxcpus"
setting, then we wouldn't need to do this dangerous scanning.
Preferably a file in /proc or /sys, though even an ioctl() would do.
This issue is on Red Hat Engineering's list of planned work items
for the upcoming Red Hat Enterprise Linux 4.4 release. Engineering
resources have been assigned and barring unforeseen circumstances, Red
Hat intends to include this item in the 4.4 release.
Yep -- got all that. The issue is that x86_apicid is not defined for i386 :(
I'll have to do some more thinkin' about the 32 bit side of things ...
committed in stream U4 build 35.3. A test kernel with this patch is available
I only see 35.2 there... what's the story?
Oh, nevermind, I see what you're saying.
seems like the first attempt to debug this would just to try loading the module
on say a U2 install, it'll be easiest to debug there if there's a problem with
Looks good as far as the kernel module itself is concerned. This is from an
Intel single dual-core CPU box.
[root@dhcp59-204 ~]# modprobe lapic_status
[root@dhcp59-204 ~]# cat /proc/lapics
0 0 1
1 -1 1
[root@dhcp59-204 ~]# uname -a
Linux dhcp59-204.rdu.redhat.com 2.6.9-39.EL #1 Thu Jun 1 17:47:54 EDT 2006
x86_64 x86_64 x86_64 GNU/Linux
I assume you loaded that on demand (ie, by using modprobe/lsmod)?
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
*** Bug 200746 has been marked as a duplicate of this bug. ***