kern/53931: posix_fadvise_reg test case fails randomly on real hardware

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

>Number:         53931
>Category:       kern
>Synopsis:       posix_fadvise_reg test case fails randomly on real hardware
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Feb 01 15:30:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The posix_fadvise_reg test case of the lib/libc/sys/t_posix_fadvise
test program is failing randomly on real amd64 hardware, with six
failures in the last 30 runs on my bare metal testbed.  It fails
with the message

  t_posix_fadvise.c:135: errno != 999: got: Operation already in progress

Log output from the latest failure:

  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/2019/2019.01.31.00.27.52/test.html#lib_libc_sys_t_posix_fadvise_posix_fadvise_reg

The first recorded failure was with source date 2015.10.30.03.08.56:

  http://www.gson.org/netbsd/bugs/build/amd64-baremetal/2015/2015.10.30.03.08.56/test.html#lib_libc_sys_t_posix_fadvise_posix_fadvise_reg

It's passing reliably on the qemu-based TNF testbed, with no failures
in 2018 nor any in 2019 so far.

>How-To-Repeat:

>Fix: