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Bug 81396 - /proc/cpuinfo contains bogus values for SMP kernels on non-hyperthreaded processors
/proc/cpuinfo contains bogus values for SMP kernels on non-hyperthreaded proc...
Product: Red Hat Linux
Classification: Retired
Component: kernel (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: Arjan van de Ven
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2003-01-08 18:24 EST by Michael J. Saletnik
Modified: 2007-04-18 12:49 EDT (History)
0 users

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2004-09-30 11:40:22 EDT
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Description Michael J. Saletnik 2003-01-08 18:24:10 EST
Description of problem:
Red Hat has ported some of the hyperthreading support from the 2.5 to the 2.4
kernels. In particular, code which prints "Physical processor ID" and "Number of
siblings" in /proc/cpuinfo has been added as linux-2.4.18-cpuinfo-siblings.patch
as of kernel-2.4.18-18.7.x

However, although this is #ifdef'd for SMP kernels, if you look at the 2.5
series (arch/i386/kernel/cpu/proc.c) you will see that it also has to be wrapped
in an if (cpu_has_ht) test.

Otherwise, running on a non-hyperthreaded-cpu SMP system, the physical id and
number of siblings will print out uninitialized values, possibly different each

Version-Release number of selected component (if applicable):
kernel-2.4.18-18.7.x and newer

How reproducible:

Steps to Reproduce:
1. On an SMP system without hyperthreaded cpus:
   while /bin/true ; do egrep 'Physical|sibling' /proc/cpuinfo ; done
Actual results:
Physical processor ID   : 591210800
Number of siblings      : 1
Physical processor ID   : 741353507
Number of siblings      : 1

Expected results:
Nothing at all - this should not be displayed for non-hyperthreaded cpu's.

Additional info:
Comment 1 Bugzilla owner 2004-09-30 11:40:22 EDT
Thanks for the bug report. However, Red Hat no longer maintains this version of
the product. Please upgrade to the latest version and open a new bug if the problem

The Fedora Legacy project (http://fedoralegacy.org/) maintains some older releases, 
and if you believe this bug is interesting to them, please report the problem in
the bug tracker at: http://bugzilla.fedora.us/

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