linux-kernel - Re: [PATCH 3/5] thermal/core: Remove unneeded mutex

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Date:   Thu, 19 Jan 2023 13:11:21 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Zhang, Rui" <rui.zhang@...el.com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amitk@...nel.org" <amitk@...nel.org>
Subject: Re: [PATCH 3/5] thermal/core: Remove unneeded mutex_destroy()

On Thu, Jan 19, 2023 at 10:30 AM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> On 19/01/2023 08:41, Zhang, Rui wrote:
> > On Wed, 2023-01-18 at 22:11 +0100, Daniel Lezcano wrote:
> >> If the thermal framework fails to initialize, the mutex can be used
> >> by
> >> the different functions registering a thermal zone anyway.
> >
> > Hmm, even with no governors and unregistered thermal sysfs class?
> >
> > IMO, thermal APIs for registering a thermal_zone/cooling_device should
> > yield early if thermal_init fails.
> > For other APIs that relies on a valid
> > thermal_zone_device/thermal_cooling_device pointer, nothing needs to
> > be changed.
> >
> > what do you think?
>
> I think you are right.
>
> It would be nice if we can check if the thermal class is registered and
> bail out if not. But there is no function to check that AFAICS.
>
> Alternatively we can convert the thermal class static structure to a
> pointer and set it to NULL in case of error in thermal_init() ?

It doesn't matter if this is a NULL pointer or a static object that's
clearly marked as unused.