[Consortium ] 6/12 March 2017


This is my weekly ChangeLog, from 6 March 2017 to 12 March 2017.
You can see it in a better format by going here: http://log.smallworks.eu/web/search?from=6/3/2017&to=12/3/2017


10 March 2017:

* === libgit2(ssh) and linux
An update on the libgit2 (and consequently iceberg) problem on linux: SSH will not work on ITIMER VM (which is the zeroconf default, at least for now).

Here the reason:

ITIMER sends an signal to the VM thread using +pthread_kill(tickerThread, TICKER_SIGNAL)+ and that aborts system calls, which are used by +libssh2+, producing a ‘wait for packet’ to fail answering a timeout ( even if that timeout does not happens for real).

Here is an interesting comment from +sqUnixITimerTickerHeartbeat.c+ :

/* While we use SA_RESTART to ensure system calls are restarted, this is
* not universally effective. In particular, connect calls can abort if
* a system call is made in the signal handler, i.e. the pthread_kill in
* prodHighPriorityThread. So we avoid this if possible by not prodding
* the high-priority thread unless there are high-priority tickees as
* indicated by numAsyncTickees > 0.

… and sadly, as +OSSubprocess+, +libssh2+ calls falls under the category of “not universally effective”(they are connect calls… once disconnected, you cannot connect again ‘as is’).

So, the only workaround possible (at least for now), is to use the threaded version of VM… I improved the error message it throws when this fails, now looks like this:

You need to add a conf file to /etc/security/limits.d, executing this:

sudo cat >/etc/security/limits.d/%s.conf <<END\n”, VMNAME);
* hard rtprio 2
* soft rtprio 2

You need to log out and log back in for the limits to take effect.
For more information read https://github.com/OpenSmalltalk/opensmalltalk-vm/releases/tag/r3732#linux

which at least shows what’s happens and how you can easily fix it.

Now, I think this is a *sad solution*. Needing to touch system configuration in order to run a VM does not feels “professional”. I would like to have some time to find a fix.





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