0ace9335e1
We need to retry to opening of the watchdog, because the device becomes
available asynchronously.
The watchdog is opened in two places:
- in pid1 in the main loop. The loop has a ratelimit, but during a boot we
iterate in it fairly quickly. On my test VM with 'iTCO_wdt', version 2:
$ journalctl -b --grep 'Failed to open any watchdog'|wc -l
3398
After the device has been processed by udev, it is initialized successfully.
- in shutdown. In that case, we most likely don't need to try more than once,
because we mostly care about the case where the watchdog device was present
and configured previously. But in principle it is possible that we might
attempt shutdown while the machine was initializing, so we don't want to
disable retries. Nevertheless, watchdog_ping() is called from a loop that
might be fairly tight, so we could end up trying to reopen the device fairly
often. This probably doesn't matter *too* much, but it's still ugly to try to
open the device without any ratelimit.
Usually the watchdog timeout would be set to something like 30 s or a few
minutes. OTOH, on my VM, the device becomes avaiable at 4.35 s after boot. So
let's use 5 s as a value that is small enough to be much smaller than any
normal watchdog timeout, but large enough that we can expect to do no more than
a 1-2 retries during a normal boot.
System and Service Manager
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