[LEDE-DEV] procd: service instance restart does not wait for old process to be closed before lanching the new one

[Alin Năstac]

Hi John,

One of the daemons I use takes sometime a couple of seconds to close
after receiving SIGTERM, so when I issue "/etc/init.d/mydaemon
restart" there will be 2 instances of that service running in parallel
until the initial instance will finally manage to handle the SIGTERM
signal. This daemon registers its own ubus object, but new instance
will fail to register its object due to name conflict with an object
that is already existing.

The root cause of this defect is the way procd restarts a service by
issuing a service_stop followed immediately by a service_start:
  1) service_stop call translates to
    - instance_stop() ->  send SIGTERM signal to the old instance
    - instance_free() -> call uloop_process_delete(), which means
in->proc.pending will be set to 0
  2) sevice_start will launch the new instance becaise previous
process has been already deleted

Shouldn't uloop_process_delete() be called only when process was
closed, as it is the case in uloop.c? If so, instance_start() should
at least set restart to 1 when (in->proc.pending && in->halt).

And isn't a bit too optimistic to assume all daemons will be stopped by SIGTERM?

BR,
Alin