Messages in this thread | | | Date | Mon, 5 Jan 2009 22:07:25 +0000 (GMT) | From | "Maciej W. Rozycki" <> | Subject | Re: [regression 2.6.27.10 & 2.6.28] \"nolapic\" option causes \"nosmp\"? |
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On Mon, 5 Jan 2009, Tetsuo Handa wrote:
> Adding "nolapic" option to kernel command line causes /proc/cpuinfo to show > only 1 CPU, while the machine has 2 CPUs and the kernel was compiled with > CONFIG_SMP=y. > > Something is wrong with CPU recognition/initialization code?
This is correct behaviour. The hardware uses the local APIC to communicate between CPUs. With the subsystem disabled there is no way to reach secondary CPUs on a standard x86 system.
> This topic is continued from http://lkml.org/lkml/2008/12/30/104 . > I confirmed that this problem occurs on native Ubuntu 8.04 (i386) and > native CentOS 5.2 (x86_64) on ThinkPad X60 (Core 2 Duo). > > Kernel 2.6.26.8 seems to be OK.
If this is the case, then "nolapic" must have been dysfunctional in that version of the kernel.
Maciej
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