[systemd-devel] bug 88401 / daemon-reload causes Type=oneshot services to be re-started / path_coldplug() is non-deserialization-aware

[Ivan Shapovalov]

On 2015-01-18 at 04:21 +0300, Ivan Shapovalov wrote:
> Hi folks,
> 
> I'm trying to fix this bug:
> https://bugs.freedesktop.org/show_bug.cgi?id=88401
> 
> The initial problem (as reported) looks following: performing a reload
> (maybe implicitly) re-starts alsa-restore.service if it is enabled.
> 
> With a bit of debugging I've apparently found a root cause. Explanation
> following.
> 
> Suppose we have CUPS installed and org.cups.cupsd.{path,service} are
> started.
> 
> We enter manager_reload(), units are serialized, reset, re-read,
> deserialized and then cold-plugged. (Note that e. g. unit_notify() has
> special "protection" to avoid spawning jobs when a reload is in
> progress.)
> 
> So, if org.cups.cupsd.path is started, *it is almost first to be
> cold-plugged*. The call chain is:
> 
> unit_coldplug()
> path_coldplug()
> path_enter_waiting() // recheck == true
> path_check_good() // returns true
> path_enter_running()
> manager_add_job() // at this point we're fucked up
> 
> So, a job is enqueued for org.cups.cupsd.service. This is already wrong,
> because a reload should never enqueue any jobs (IIUC). So, the job is
> enqueued... remember that almost all units are inactive by now. Thus we
> end up re-starting half a system (the whole basic.target) as
> dependencies.
> 
> Questions:
> - is my analysis correct?
> - if yes, then how to fix this? Maybe add a similar
>   "if (UNIT(p)->manager->n_reloading <= 0)" check to
>   path_enter_running() to avoid calling manager_add_job() during
>   reloading?

Anyone?

-- 
Ivan Shapovalov / intelfx /
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