port-arm/55385: ARM testbeds hang running lib/libpthread/t_mutex test

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         55385
>Category:       port-arm
>Synopsis:       ARM testbeds hang running lib/libpthread/t_mutex test
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Jun 14 08:50:00 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2020.06.04.00.45.32
>Organization:
>Environment:
System: NetBSD
Architecture: earmv7hf
Machine: evbarm
>Description:

The TNF evbarm-earmv7hf and evbarm-aarch64 testbeds are both hanging
at the mutex5 test case of the lib/libpthread/t_mutex test:

  lib/libpthread/t_mutex (407/847): 7 test cases
      mutex1: [606.695610s] Failed: Test case timed out after 300 seconds
      mutex2: [604.408457s] Failed: Test case timed out after 300 seconds
      mutex3: [602.468435s] Failed: Test case timed out after 300 seconds
      mutex4: [604.340654s] Failed: Test case timed out after 300 seconds
      mutex5:

Note that this is the whole test run hanging, not just an individual
test case.

The problem started with this commit:

  2020.06.04.00.45.32 joerg src/external/bsd/jemalloc/dist/src/tsd.c 1.3
  2020.06.04.00.45.32 joerg src/external/bsd/jemalloc/include/jemalloc/internal/jemalloc_internal_defs.h 1.13
  2020.06.04.00.45.32 joerg src/lib/libpthread/pthread.c 1.174

Logs:

  http://releng.netbsd.org/b5reports/evbarm-earmv7hf/commits-2020.06.html#2020.06.04.00.45.32
  http://releng.netbsd.org/b5reports/evbarm-aarch64/commits-2020.06.html#2020.06.04.00.45.32

>How-To-Repeat:

Run the ATF tests on arm.

>Fix: