[llvm-bugs] [Bug 45556] New: Threading.PhysicalConcurrency test fails when available cpus < physical cpus

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45556

            Bug ID: 45556
           Summary: Threading.PhysicalConcurrency test fails when
                    available cpus < physical cpus
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Support Libraries
          Assignee: unassignedbugs at nondot.org
          Reporter: john.brawn at arm.com
                CC: llvm-bugs at lists.llvm.org

If I do
 taskset -c 0 ./unittests/Support/SupportTests
--gtest_filter=Threading.PhysicalConcurrency
then the test fails with
 /home/jb/work/llvm-project/llvm/unittests/Support/Threading.cpp:25: Failure
 Expected: (Num.compute_thread_count()) <=
(hardware_concurrency().compute_thread_count()), actual: 4 vs 1

Num.compute_thread_count() examines /proc/cpuinfo which (on my machine) says
there are 4 cpus, hardware_concurrency().compute_thread_count() calls
sched_getaffinity which says there's one available cpu.

It looks like the commit that caused this to fail is:

commit 8404aeb56a73ab24f9b295111de3b37a37f0b841
Author: Alexandre Ganea <alexandre.ganea at ubisoft.com>
Date:   Thu Feb 13 22:49:57 2020 -0500

    [Support] On Windows, ensure hardware_concurrency() extends to all CPU
sockets and all NUMA groups

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