Casu firmware locks

[marselap]

Description:

When casu-fw is run from /etc/rc.local, it locks after 15-100 seconds and stays idle for around 100 s. Upon unlocking, continues to run normally until a new lock.

• When the firmware is run manually, no lock occurs.
• When only one firmware is run, no locking occurs.
• With two firmwares on the same bus, problem does occur.

Cause:

Probable cause in lockf used to protect i2c bus usage. Unclear why all 4 firmwares lock at the same time (at least one uses other bus which should not be affected by lockf to other bus).

Current solution:

Temporary workaround: redirect stdout (and stderr) to /dev/null (or any other file). Probably works because writing to a file slows down the process. Expected firmware locking in long firmware runs.

TODO:

Check if lockf is a problem. Check why firmwares unlock (lock timeout?). Unclear why only when run at boot, and not when run manually.

[marselap]

From #48 "Should check if issue persists with current version of the firmware."

[marselap]

It seems the problem is with systemd-journal which by default logs stdout and stderr to /run/log/journal and blocks process for a reason. Workaround is setting journal log destination to /dev/null and/or changing logging priority
solved here
Prettier solution is stdout/stderr redirection in /etc/systemd/journald.conf, but this works for now.

We should change the firmware so that the debug output is optional at firmware start, not to flood stdout when unnecessary. Stderr will be used for error and exception logging (issue #45).