linux-kernel - Re: [PATCH v1 3/3] thermal: core: Rework thermal zone availability check

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Date:   Tue, 12 Dec 2023 11:28:58 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>
Cc:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Lukasz Luba <lukasz.luba@....com>
Subject: Re: [PATCH v1 3/3] thermal: core: Rework thermal zone availability
 check

On 08/12/2023 20:20, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> In order to avoid running __thermal_zone_device_update() for thermal
> zones going away, the thermal zone lock is held around device_del()
> in thermal_zone_device_unregister() and thermal_zone_device_update()
> passes the given thermal zone device to device_is_registered().
> This allows thermal_zone_device_update() to skip the
> __thermal_zone_device_update() if device_del() has already run for
> the thermal zone at hand.
> 
> However, instead of looking at driver core internals, the thermal
> subsystem may as well rely on its own data structures for this
> purpose.  Namely, if the thermal zone is not present in
> thermal_tz_list, it can be regarded as unavailable, which in fact is
> already the case in thermal_zone_device_unregister().  Accordingly,
> the device_is_registered() check in thermal_zone_device_update() can
> be replaced with checking whether or not the node list_head in struct
> thermal_zone_device is empty, in which case it is not there in
> thermal_tz_list.
> 
> To make this work, though, it is necessary to initialize tz->node
> in thermal_zone_device_register_with_trips() before registering the
> thermal zone device and it needs to be added to thermal_tz_list and
> deleted from it under its zone lock.
> 
> After the above modifications, the zone lock does not need to be
> held around device_del() in thermal_zone_device_unregister() any more.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>


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