bug#33239: 'guix offload' regularly hangs in 'channel-get-exit-status' call

["Ludovic Courtès" <ludo@gnu.org>]

Hello!

Ludovic Courtès <ludo@gnu.org> skribis:

> ludo@gnu.org (Ludovic Courtès) skribis:
>
>> The ‘guix offload’ processes on berlin regularly hang while calling
>> ‘channel-get-exit-status’:
>>
>> (gdb) bt
>> #0  0x00007f299fb330f1 in __GI___poll (fds=0x1dd58c0, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
>> #1  0x00007f2994287577 in ssh_poll_ctx_dopoll () from target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
>> #2  0x00007f29942884d9 in ssh_handle_packets () from target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
>> #3  0x00007f29942885ad in ssh_handle_packets_termination () from target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
>> #4  0x00007f2994275080 in ssh_channel_get_exit_status () from target:/gnu/store/wmpg67bn7i7pqc0p4xjp1npnqixk9znd-libssh-0.7.6/lib/libssh.so.4
>> #5  0x00007f29946dd11a in guile_ssh_channel_get_exit_status () from target:/gnu/store/i3nfl17wfx7sryq6w15r9wxl7ilmq4rb-guile-ssh-0.11.3/lib/libguile-ssh.so.11
>> #6  0x00007f29a1765965 in vm_regular_engine (thread=0x1dd58c0, vp=0x1d4df30, registers=0xffffffff, resume=-1615646479) at vm-engine.c:786
>
> I was able to come up with a reduced test case for Guile-SSH:
>
>   https://github.com/artyom-poptsov/guile-ssh/issues/11

It turned out that the code to start a REPL server in (ssh dist node)
would currently hang, as I wrote in the bug report above.

After investigation, I decided that inferiors are more appropriate than
Guile-SSH’s node to address this use case, after all.  Commit
ed7b44370f71126087eb953f36aad8dc4c44109f changes ‘guix offload’ to
inferiors.

As a result, build machines must now run Guix > 0.15.0, which provides
‘guix repl’.  That in turn simplifies setup of build machines: no need
to fiddle with GUILE_LOAD_PATH.

On berlin, build machines were running an older Guix so I copied a
recently pulled Guix on each of them and installed it in
~/.config/guix/current.  They’re now operational, except for the ARMv7
one which is still pulling.  So far it seems to be working well but
we’ll have to keep an eye on it.

Thanks,
Ludo’.