In some cases the main/control PID of a service can be outside of the
services cgroups (for example, if logind readjusts the processes'
cgroup). In order to clarify this for the user show the main/control PID
in the cgroup tree nonetheless, but mark them specially.
Previously, we were brutally and onconditionally killing all processes
in a service's cgroup before starting the service anew, in order to
ensure that StartPre lines cannot be misused to spawn long-running
processes.
On logind-less systems this has the effect that restarting sshd
necessarily calls all active ssh sessions, which is usually not
desirable.
With this patch control processes for a service are placed in a
sub-cgroup called "control/". When starting a service anew we simply
kill this cgroup, but not the main cgroup, in order to avoid killing any
long-running non-control processes from previous runs.
https://bugzilla.redhat.com/show_bug.cgi?id=805942
gettys are nowadays mostly autospawned and hence usually subject to
being shut down on isolate requests, since they are no dependency of any
other unit. This is a bad idea if the user isolates between
multi-user.graphical and graphical.target, hence exclude them from the
isolation.
This has the effect that gettys no longer cleaned up when
emergency.target is isolated, which might actualy be considered a
feature, even though it is a change from previous behaviour...
Note that the one getty that really matters (the one on tty1) is still
removed when isolating to emergency.target since it conflicts with
emergency.service.
This adds minimal hardware watchdog support to PID 1. The idea is that
PID 1 supervises and watchdogs system services, while the hardware
watchdog is used to supervise PID 1.
This adds two hardware watchdog configuration options, for the runtime
watchdog and for a shutdown watchdog. The former is active during normal
operation, the latter only at reboots to ensure that if a clean reboot
times out we reboot nonetheless.
If the runtime watchdog is enabled PID 1 will automatically wake up at
half the configured interval and write to the watchdog daemon.
By default we enable the shutdown watchdog, but leave the runtime
watchdog disabled in order not to break independent hardware watchdog
daemons people might be using.
This is only the most basic hookup. If necessary we can later on hook
up the watchdog ping more closely with services deemed crucial.
This logic can be turned off by defining SD_JOURNAL_SUPPRESS_LOCATION
before including sd-journal.h.
This also saves/restores errno in all logging functions, in order to be
useful as logging calls without side-effects.
This also adds a couple of __unlikely__ around the early checks in the
logging calls, in order to minimize the runtime impact.
