[Bug libc/28865] linux: _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN are inaccurate without /sys and /proc

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28865

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The release/2.35/master branch has been updated by Dmitry Levin
<ldv@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=491f2ef1f0ff849490f374917957018d07ee0586

commit 491f2ef1f0ff849490f374917957018d07ee0586
Author: Dmitry V. Levin <ldv@altlinux.org>
Date:   Sat Feb 5 08:00:00 2022 +0000

    linux: fix accuracy of get_nprocs and get_nprocs_conf [BZ #28865]

    get_nprocs() and get_nprocs_conf() use various methods to obtain an
    accurate number of processors.  Re-introduce __get_nprocs_sched() as
    a source of information, and fix the order in which these methods are
    used to return the most accurate information.  The primary source of
    information used in both functions remains unchanged.

    This also changes __get_nprocs_sched() error return value from 2 to 0,
    but all its users are already prepared to handle that.

    Old fallback order:
      get_nprocs:
        /sys/devices/system/cpu/online -> /proc/stat -> 2
      get_nprocs_conf:
        /sys/devices/system/cpu/ -> /proc/stat -> 2

    New fallback order:
      get_nprocs:
        /sys/devices/system/cpu/online -> /proc/stat -> sched_getaffinity -> 2
      get_nprocs_conf:
        /sys/devices/system/cpu/ -> /proc/stat -> sched_getaffinity -> 2

    Fixes: 342298278e ("linux: Revert the use of sched_getaffinity on
get_nproc")
    Closes: BZ #28865
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

    (cherry picked from commit e1d32b836410767270a3adf1f82b1a47e6e4cd51)

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