kern/56499: v7fs_renamerace_cycle test case randomly fails

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

>Number:         56499
>Category:       kern
>Synopsis:       v7fs_renamerace_cycle test case randomly fails
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Nov 15 11:05:00 +0000 2021
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:
  
>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

When I run the ATF tests on real amd64 hardware, the
v7fs_renamerace_cycle test case fails with the error message
"Test program received signal 14" in roughly 1 out of every 30 runs.
The log output from a recent failure is here:

  https://www.gson.org/netbsd/bugs/build/amd64-baremetal/2021/2021.11.11.07.38.21/test.html#fs_vfs_t_renamerace_v7fs_renamerace_cycle

Signal 14 is a SIGALRM, which presumably comes from this piece of
code in src/tests/fs/vfs/t_renamerace.c:

        alarm(1);
        pthread_join(pt_rmdir, NULL);
        pthread_join(pt_rename1, NULL);
        pthread_join(pt_rename2, NULL);
        alarm(0);

The problem still occurs if I change the alarm(1) to alarm(10), so
this appears to be a deadlock of some sort rather than just the
timeout being too short.

>How-To-Repeat:

>Fix: