[FS#1481] procd: Not possible to stop procd task when in respawning state

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Oldřich Jedlička (oldium) 

Attached to Project - OpenWrt/LEDE Project
Summary - procd: Not possible to stop procd task when in respawning state
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Problem: when using procd init scripts, the started service cannot be stopped, when the respawning is in progress.

The test case for the simple start/stop case is attached. Save attached shell scripts procd-test in /etc/init.d, run-test in / and run the test - the /run-test.log output is attached too.

Same can be observed in more complicated test scripts too, for example removing a respawning service instance is not possible (switch from one instance to no instance - procd should just watch the registered configuration/interfaces for changes and restart when change happens) - the instance is still listed in "ubus call service list" and is actively respawning.

This is a problem, because when for example the service is running on PPPoE interface, which goes down for a minute, the service fails and is respawned several times by procd even when the init script tried to remove the instance. As a multi-fail consequence, the procd removes the respawn parameters and does not reintroduce them when the PPPoE is back up and the init script starts the instance again. Result is a started service, but with no respawning.

Expected result: procd should stop respawning as soon as possible and apply the requested changes afterwards.

Tested on OpenWrt git master (from github) on TP-Link TL-WR1043ND and on x86/64bit Hyper-V virtual machine (VDI converted to VHDX), both give the same result.

One or more files have been attached.

More information can be found at the following URL:
https://bugs.openwrt.org/index.php?do=details&task_id=1481