CTDB: simple/90_debug_hung_script.sh test fails on some machines

[Tim Beale]

Hi,

I noticed a problem trying to run the samba_build_ctdb test on the
rackspace machines. The tests/simple/90_debug_hung_script.sh test-case
seems to reliably fail.

I could reproduce the failure by running the ctdb autobuild on my PC.
Basically the test is failing because the 'cat "/proc/${pid}/stack"' in
debug-hung-script.sh fails (Operation not permitted). The reason for the
failure seems to be the Yama ptrace_scope setting on the host machine.
https://www.kernel.org/doc/Documentation/security/Yama.txt

My PC had kernel.yama.ptrace_scope set to 1. If I set it to zero, then
the CTDB test passes. It seems like the gitlab CI machines must use a
ptrace_scope=0 setting.

Any idea what to do here? It seems like we'd want the
debug-hung-script.sh to still do something useful even if
yama.ptrace_scope=1.

Thanks,
Tim