[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAPDyKFqzxnfh0kow5mzoApFMQpKOAv=e1b7Cy9H-iEh99Wmagw@mail.gmail.com>
Date: Fri, 7 Jan 2022 16:54:01 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: rjw@...ysocki.net, lukasz.luba@....com, robh@...nel.org,
heiko@...ech.de, arnd@...aro.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
Daniel Lezcano <daniel.lezcano@...nel.org>
Subject: Re: [PATCH v5 2/6] powercap/drivers/dtpm: Add hierarchy creation
[...]
> >> +static int dtpm_for_each_child(const struct dtpm_node *hierarchy,
> >> + const struct dtpm_node *it, struct dtpm *parent)
> >> +{
> >> + struct dtpm *dtpm;
> >> + int i, ret;
> >> +
> >> + for (i = 0; hierarchy[i].name; i++) {
> >> +
> >> + if (hierarchy[i].parent != it)
> >> + continue;
> >> +
> >> + dtpm = dtpm_node_callback[hierarchy[i].type](&hierarchy[i], parent);
> >> + if (!dtpm || IS_ERR(dtpm))
> >> + continue;
> >> +
> >> + ret = dtpm_for_each_child(hierarchy, &hierarchy[i], dtpm);
> >
> > Why do you need to recursively call dtpm_for_each_child() here?
> >
> > Is there a restriction on how the dtpm core code manages adding
> > children/parents?
>
> [ ... ]
>
> The recursive call is needed given the structure of the tree in an array
> in order to connect with the parent.
Right, I believe I understand what you are trying to do here, but I am
not sure if this is the best approach to do this. Maybe it is.
The problem is that we are also allocating memory for a dtpm and we
call dtpm_register() on it in this execution path - and this memory
doesn't get freed up nor unregistered, if any of the later recursive
calls to dtpm_for_each_child() fails.
The point is, it looks like it can get rather messy with the recursive
calls to cope with the error path. Maybe it's easier to store the
allocated dtpms in a list somewhere and use this to also find a
reference of a parent?
Later on, when we may decide to implement "dtpm_destroy_hierarchy()"
(or whatever we would call such interface), you probably need a list
of the allocated dtpms anyway, don't you think?
[...]
Kind regards
Uffe
Powered by blists - more mailing lists