LinuxQuestions.org
Review your favorite Linux distribution.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Newbie
User Name
Password
Linux - Newbie This Linux forum is for members that are new to Linux.
Just starting out and have a question? If it is not in the man pages or the how-to's this is the place!

Notices


Reply
  Search this Thread
Old 06-11-2010, 11:15 AM   #1
ertl
LQ Newbie
 
Registered: Jun 2010
Posts: 3

Rep: Reputation: 0
Missing CPU Core on Boot


I'm running Linux on an Intel Core 2 Duo processor. When I apply power to my computer, it boots into one core but appears to leave the other one idle. On the screen, it prints:

....
SMP: Allowing 2 CPUs, 1 hotplug CPUs
.....

I can confirm that only 1 CPU is active by logging in and examining /proc/interrupts and /proc/cpuinfo. After issuing a "reboot" command, the screen shows:

...
SMP: Allowing 2 CPUs, 0 hotplug CPUs
...

So, when I do a cold boot, I one get 1 CPU. When I do a warm boot, I get both CPUs. This is a problem for me because I'm running Linux on an embedded board and I need both CPUs to be running.

I've played around with BIOS settings, the boot string, kernel configuration, and CPU hot plugging. I can't seem to find a way to get both processors running without booting the system twice.

I thought that the CPU hot plugging path showed some promise but I can't seem to get that feature working on my system. The first issue is that the Linux documentation doesn't seem to match with what I'm seeing. It states that you should be able to go into /sys/devices/system/cpu/cpuX/ and write a zero or a one to the file labeled 'online' to disable it or enable it. When I go to /sys/devices/system/cpu I only see a directory for cpu0. There isn't a directory for cpu1.

After a reboot, I do see two directories int /sys/devices/system/cpu (cpu0 and cpu1). At this point, it won't let me 'offline' the second processor. The echo command gives me an error. (By the Way: the 'online' file in each cpuX directory has read only permissions.) This error occurs after I've changed the permissions on the file to read/write.

I confirmed that the following parameters are set in my .config file: CONFIG_HOTPLUG, CONFIG_HOTPLUG_CPU, CONFIG_SMP, CONFIG_SUSPEND_SMP

I've done searches on google until my eyes popped out and can't find much information. I see others have had similar problems but they all seem to link back to ACPI in BIOS. I've already played with all of those settings and I didn't see any effect. One reason I don't think it's a BIOS problem is because a warm boot (reboot) seems to 'fix' it.

I've tried different kernels, different distributions, and different computers. I see similar behavior in all configurations. I feel like I'm missing something fundamental.

Any help or ideas would be greatly appreciated!

Thanks.
 
Old 06-11-2010, 12:34 PM   #2
amani
Senior Member
 
Registered: Jul 2006
Location: Kolkata, India
Distribution: Debian 64-bit GNU/Linux, Kubuntu64, Fedora QA, Slackware,
Posts: 2,766

Rep: Reputation: Disabled
It does look like a bios feature
 
Old 06-11-2010, 01:07 PM   #3
onebuck
Moderator
 
Registered: Jan 2005
Location: Midwest USA, Central Illinois
Distribution: SlackwareŽ
Posts: 12,716
Blog Entries: 27

Rep: Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058
Hi,

Welcome to LQ!

Since you are running an embed why not use the supported distribution & toolbox? Which board are you using? Most manufactures do have a streamlined/custom distribution to use for their systems.
 
Old 06-14-2010, 03:08 PM   #4
ertl
LQ Newbie
 
Registered: Jun 2010
Posts: 3

Original Poster
Rep: Reputation: 0
Thumbs up

I emailed the manufacturer of my embedded board and gave them a detailed description about this problem. After some investigation, they determined that the BIOS is somehow getting confused.

On some cold boots, the BIOS thinks the board is coming out of a standby mode instead of a cold boot. When it comes out of standby, the BIOS doesn't reload the ACPI tables that are necessary for Linux to bring up both CPU cores. They are sending me an updated BIOS image.

Thanks for suggesting that I contact the manufacturer.
 
Old 06-14-2010, 03:17 PM   #5
onebuck
Moderator
 
Registered: Jan 2005
Location: Midwest USA, Central Illinois
Distribution: SlackwareŽ
Posts: 12,716
Blog Entries: 27

Rep: Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058Reputation: 2058
Hi,

Glad to hear things are looking better.

Thanks for the feedback.

BTW, as the OP you can mark this thread as [Solved] via the Thread Tools.

 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
Get process running CPU core and the utilisation on that core... chamila1986 Programming 5 04-28-2010 05:00 PM
cpu frequency scaling with Pentium(R) Dual-Core CPU E5200 @ 2.50GHz tramni1980 Slackware 5 08-16-2009 08:29 AM
Can you install two OS on a dual-core computer (one OS on each CPU core?) kushalkoolwal Linux - Software 7 10-17-2008 05:57 AM
Boot with 'acpi=no'-Ubuntu shows one core,normal boot-kacpid process is eating 70%CPU WebEyeX Ubuntu 5 05-18-2008 06:48 AM
Intel DG33FB motherboard - cannot run second core on cpu (core 2 duo) rmitev Linux - Enterprise 2 09-28-2007 04:54 AM


All times are GMT -5. The time now is 02:59 AM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration