kern/54842: Various NFS tests now fail randomly

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

>Number:         54842
>Category:       kern
>Synopsis:       Various NFS tests now fail randomly
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 07 16:35:01 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:

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

Various NFS tests that used to reliably pass are now randomly failing
on my i386 testbed running on real 8-core hardware, since some time
around the new year.  You can find a number of such failures by
searching for "nfs" in this summary report for January 2020:

  http://www.gson.org/netbsd/bugs/build/i386-baremetal/commits-2020.01.html

Here are direct links to a few of the latest failures:

  http://www.gson.org/netbsd/bugs/build/i386-baremetal/2020/2020.01.06.11.24.30/test.html#fs_vfs_t_io_nfs_extendfile
  http://www.gson.org/netbsd/bugs/build/i386-baremetal/2020/2020.01.06.11.24.30/test.html#fs_vfs_t_vfsops_nfs_tfhinval
  http://www.gson.org/netbsd/bugs/build/i386-baremetal/2020/2020.01.06.21.04.58/test.html#fs_vfs_t_renamerace_nfs_renamerace_dirs
  http://www.gson.org/netbsd/bugs/build/i386-baremetal/2020/2020.01.06.21.04.58/test.html#fs_vfs_t_unpriv_nfs_dirperms

Contrast with the lack of such failures in December 2019:

  http://www.gson.org/netbsd/bugs/build/i386-baremetal/commits-2019.12.html

>How-To-Repeat:

>Fix: