os: test is timing out on plan9-arm

[millerresearch]

The os test has been timing out on plan9-arm after 18m on every run, apparently since CL313514

[millerresearch]

The TestExecutableDeleted test is hanging when subprocess testdel.exe goes into Plan 9 "Broken" state instead of exiting. This behaviour seems to be new with commit 02ab8d1.

[millerresearch]

Looking at the source of testdel.exe, I'm surprised this test has ever passed on Plan 9. The program deletes its own executable file while running, which is likely to cause it to crash because Plan 9 does demand paging directly from the executable file and doesn't protect files from deletion while being executed. I think the commit must have had the side effect of changing the program's paging behaviour such that it now touches a previously unreferenced page after the file deletion,.

This test is already skipped on windows, openbsd, freebsd, and aix. I think it should be skipped on plan9 too.

[gopherbot]

Change https://golang.org/cl/316829 mentions this issue: os: skip TestExecutableDeleted on plan9