[systemd-devel] [PATCHv2] core: do not spawn jobs or touch other units during coldplugging

[Lennart Poettering]

On Sat, 25.04.15 05:48, Ivan Shapovalov (intelfx100 at gmail.com) wrote:

> On 2015-04-25 at 04:00 +0300, Ivan Shapovalov wrote:
> > On 2015-04-24 at 16:04 +0200, Lennart Poettering wrote:
> > > [...]
> > > 
> > > Actually, it really is about the UNIT_TRIGGERS dependencies only,
> > > since we don't do the retroactive deps stuff at all when we are
> > > coldplugging, it's conditionalized in m->n_reloading <= 0.
> > 
> > So, I think I understand the problem. We should do this not only for
> > UNIT_TRIGGERS, but also for any dependencies which may matter
> > when activating that unit. That is, anything which is referenced by
> > transaction_add_job_and_dependencies()... recursively.
> 
> Here is what I have in mind. Don't know whether this is correct, but
> it fixes the problem for me.
> 
> From 515d878e526e52fc154874e93a4c97555ebd8cff Mon Sep 17 00:00:00 2001
> From: Ivan Shapovalov <intelfx100 at gmail.com>
> Date: Sat, 25 Apr 2015 04:57:59 +0300
> Subject: [PATCH] core: coldplug all units which participate in jobs
> 
> This is yet another attempt to fix coldplugging order (more especially,
> the problem which happens when one creates a job during coldplugging, and
> it references a not-yet-coldplugged unit).
> 
> Now we forcibly coldplug all units which participate in jobs. This
> is a superset of previously implemented handling of the UNIT_TRIGGERS
> dependencies, so that handling is removed.
> ---
>  src/core/transaction.c | 6 ++++++
>  src/core/unit.c        | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/src/core/transaction.c b/src/core/transaction.c
> index 5974b1e..a02c02c 100644
> --- a/src/core/transaction.c
> +++ b/src/core/transaction.c
> @@ -848,6 +848,12 @@ int transaction_add_job_and_dependencies(
>          assert(type < _JOB_TYPE_MAX_IN_TRANSACTION);
>          assert(unit);
>  
> +        /* Before adding jobs for this unit, let's ensure that its state has been loaded.
> +         * This matters when jobs are spawned as part of coldplugging itself (see. e. g. path_coldplug().
> +         * This way, we "recursively" coldplug units, ensuring that we do not look at state of
> +         * not-yet-coldplugged units. */
> +        unit_coldplug(unit);

I like the simplicity of this patch actually, but it's unfortunately
too simple: coldplugging is to be applied only for services that are
around at the time we come back from a reload. If you start a service
during runtime, without any reloading anywhere around, we should not
coldplug at all.

I figure we need a "coldplugging" bool or so in Manager, which we set
while coldplugging and can then check here.

Lennart

-- 
Lennart Poettering, Red Hat