misc/51041: ATF tests hang in usr.bin/sdiff/t_sdiff:merge

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

>Number:         51041
>Category:       misc
>Synopsis:       ATF tests hang in usr.bin/sdiff/t_sdiff:merge
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    misc-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 03 18:30:00 +0000 2016
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2016.04.02.20.38.40
>Organization:

>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

The ATF tests are currently hanging during the "merge" test case of
the usr.bin/sdiff/t_sdiff test:

  babylon5.netbsd.org:/bracket/i386/results$ zgrep ' merge:' 2016*/test.log.gz | grep -v buffer | grep -v before | tail -10
  2016.04.01.12.37.48/test.log.gz:    merge: [4.647366s] Passed.
  2016.04.01.19.59.08/test.log.gz:    merge: [5.301491s] Passed.
  2016.04.01.20.21.45/test.log.gz:    merge: [3.860391s] Passed.
  2016.04.02.08.16.54/test.log.gz:    merge: [5.127778s] Passed.
  2016.04.02.08.54.47/test.log.gz:    merge: [3.616784s] Passed.
  2016.04.02.11.18.26/test.log.gz:    merge: [3.469399s] Passed.
  2016.04.02.16.18.54/test.log.gz:    merge: [4.021238s] Passed.
  2016.04.03.01.00.26/test.log.gz:    merge: Traceback (most recent call last):
  2016.04.03.01.49.51/test.log.gz:    merge: Traceback (most recent call last):
  2016.04.03.02.28.46/test.log.gz:    merge: Traceback (most recent call last):

Because of this, the remainder of the tests do not run, and even the
tests that did run are missing HTML reports.

Because the problem appeared during a period of build breakage, I
can't easily bisect it down to a single commit.  Here is the full list
of commits that could have caused it:

  2016.04.02.20.38.40 christos src/sys/kern/kern_exit.c 1.249
  2016.04.02.20.38.40 christos src/sys/sys/Makefile 1.158
  2016.04.02.20.38.40 christos src/sys/sys/idtype.h 1.1
  2016.04.02.20.38.40 christos src/sys/sys/pset.h 1.5
  2016.04.02.20.38.40 christos src/sys/sys/resource.h 1.34
  2016.04.02.20.38.40 christos src/sys/sys/wait.h 1.28
  2016.04.02.20.46.37 christos src/distrib/sets/lists/comp/mi 1.2025
  2016.04.02.21.01.32 christos src/sys/kern/syscalls.master 1.282
  2016.04.02.21.02.39 christos src/sys/kern/init_sysent.c 1.307
  2016.04.02.21.02.39 christos src/sys/kern/syscalls.c 1.297
  2016.04.02.21.02.39 christos src/sys/kern/syscalls_autoload.c 1.16
  2016.04.02.21.02.39 christos src/sys/rump/include/rump/rump_syscalls.h 1.97
  2016.04.02.21.02.39 christos src/sys/sys/syscall.h 1.291
  2016.04.02.21.02.39 christos src/sys/sys/syscallargs.h 1.275
  2016.04.02.21.02.40 christos src/sys/rump/librump/rumpkern/rump_syscalls.c 1.124
  2016.04.02.21.03.13 christos src/sys/kern/systrace_args.c 1.16
  2016.04.02.21.09.43 christos src/sys/sys/wait.h 1.29
  2016.04.02.21.21.57 christos src/sys/sys/idtype.h 1.2
  2016.04.02.22.08.14 mrg src/share/mk/bsd.own.mk 1.916
  2016.04.02.22.37.03 riastradh src/sys/external/bsd/drm2/dist/drm/via/via_drv.c 1.3
  2016.04.02.22.40.43 riastradh src/sys/external/bsd/drm2/drm/drm_lock.c 1.4
  2016.04.03.00.18.01 christos src/sys/sys/idtype.h 1.3
  2016.04.03.00.19.42 christos src/lib/libc/gen/Makefile.inc 1.194
  2016.04.03.00.19.42 christos src/lib/libc/gen/waitid.c 1.1
  2016.04.03.00.19.42 christos src/lib/libc/include/namespace.h 1.180
  2016.04.03.00.19.42 christos src/lib/libc/shlib_version 1.263
  2016.04.03.00.19.42 christos src/lib/libc/sys/Makefile.inc 1.229
  2016.04.03.00.19.42 christos src/lib/libc/sys/wait.2 1.28
  2016.04.03.00.20.22 christos src/distrib/sets/lists/base/shl.mi 1.767
  2016.04.03.00.20.22 christos src/distrib/sets/lists/comp/mi 1.2026
  2016.04.03.00.20.23 christos src/distrib/sets/lists/debug/shl.mi 1.129
  2016.04.03.00.48.29 christos src/lib/libc/sys/makelintstub 1.26
  2016.04.03.01.00.26 christos src/sys/kern/syscalls.master 1.283

I'm guessing it's not gcc 5.3 related, because sparc is also affected.

>How-To-Repeat:

Run the ATF tests.

>Fix: