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Bug 814294 - numa_all_cpus_ptr reports the wrong thing when bound to cpu0
numa_all_cpus_ptr reports the wrong thing when bound to cpu0
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: numactl (Show other bugs)
All Linux
medium Severity medium
: rc
: ---
Assigned To: Petr Holasek
Depends On:
Blocks: 782183 787802 840699
  Show dependency treegraph
Reported: 2012-04-19 10:27 EDT by Travis Gummels
Modified: 2016-10-04 00:08 EDT (History)
5 users (show)

See Also:
Fixed In Version: numactl-2.0.7-4.el6
Doc Type: Bug Fix
Doc Text:
Cause: global pointer numa_all_cpus_ptr contained all possible CPU0 when taskset was set to cpu 0. Consequence: Wrong condition in code parsing /proc/self/stat Fix: Codepath fixed. Result: numa_all_cpus_ptr contains only specified CPUs, when taskset contains cpu 0.
Story Points: ---
Clone Of:
Last Closed: 2013-02-21 05:11:27 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
Reproducer (382 bytes, application/octet-stream)
2012-04-19 10:32 EDT, Travis Gummels
no flags Details
Proposed Patch (992 bytes, patch)
2012-04-19 10:34 EDT, Travis Gummels
no flags Details | Diff

  None (edit)
Description Travis Gummels 2012-04-19 10:27:59 EDT
Description of problem:

There is a global pointer named 'numa_all_cpus_ptr' which is broken in that it doesn't function as documented.  It is supposed to be set to ' a bitmask that is allocated by the library with bits representing all cpus on which the calling  thread  may  execute.  However, this seems to not work when the bitmask is set to only CPU0

numa_all_cpus_ptr: 1111111111111111111111111111111100
Number of CPUS in numa_all_cpus_ptr: 32

$ taskset -c 4 ./t
numa_all_cpus_ptr: 0000100000000000000000000000000000
Number of CPUS in numa_all_cpus_ptr: 1

$ taskset -c 0 ./t
numa_all_cpus_ptr: 1111111111111111111111111111111100
Number of CPUS in numa_all_cpus_ptr: 32

$ taskset -c 1 ./t
numa_all_cpus_ptr: 0100000000000000000000000000000000
Number of CPUS in numa_all_cpus_ptr: 1

Note that the taskset -c0 ./t case should only have 1 bit set in the 0th position.  So it must be the code that parses /proc/self/stat Cpus_allowed.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1.  See above
Actual results:

Expected results:
Not Broken

Additional info:
LLNL has requested this bug be public.
Comment 1 Travis Gummels 2012-04-19 10:32:52 EDT
Created attachment 578663 [details]

gcc -o t -lnuma t.c
Comment 2 Travis Gummels 2012-04-19 10:34:30 EDT
Created attachment 578665 [details]
Proposed Patch

commit 346e427204fba80e86d6ebd8965610b89dc5c7d6
Author: Mark A. Grondona <>
Date:   Tue Mar 27 15:51:28 2012 -0700

    libnuma: fix numa_all_cpus_ptr when bound to cpu0
    A bug in the test for invalid maxproccpu leads to resetting the
    numa_all_cpus_ptr mask when the cpu affinity mask of the current
    task only contains CPU0. This leads to numa_all_cpus_ptr having
    all CPUs instead of just one.
    Fix the test to be < 0 instead of <= 0 -- 0 is a valid CPU number.
Comment 8 errata-xmlrpc 2013-02-21 05:11:27 EST
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

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