netdev - Re: [PATCH v7 00/11] Stop monitoring disabled devices

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Date:   Fri, 3 Jul 2020 08:38:48 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Zhang Rui <rui.zhang@...el.com>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
        netdev@...r.kernel.org, linux-wireless@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org,
        linux-rockchip@...ts.infradead.org
Cc:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Vishal Kulkarni <vishal@...lsio.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Peter Kaestle <peter@...e.net>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Sebastian Reichel <sre@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        Support Opensource <support.opensource@...semi.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        Heiko Stuebner <heiko@...ech.de>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Allison Randal <allison@...utok.net>,
        Enrico Weigelt <info@...ux.net>,
        Gayatri Kammela <gayatri.kammela@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        kernel@...labora.com
Subject: Re: [PATCH v7 00/11] Stop monitoring disabled devices

On 03/07/2020 03:49, Zhang Rui wrote:
> On Thu, 2020-07-02 at 19:49 +0200, Daniel Lezcano wrote:

[ ... ]

>>> So the reason is that ->get_temp() is called while the mutex is
>>> held and
>>> thermal_zone_device_is_enabled() wants to take the same mutex.
>>
>> Yes, that's correct.
>>
>>> Is adding a comment to thermal_zone_device_is_enabled() to never
>>> call
>>> it while the mutex is held and adding another version of it which
>>> does
>>> not take the mutex ok?
>>
>> The thermal_zone_device_is_enabled() is only used in two places, acpi
>> and this imx driver, and given:
>>
>> 1. as soon as the mutex is released, there is no guarantee the
>> thermal
>> zone won't be changed right after, the lock is pointless, thus the
>> information also.
>>
>> 2. from a design point of view, I don't see why a driver should know
>> if
>> a thermal zone is disabled or not
>>
>> It would make sense to end with this function and do not give the
>> different drivers an opportunity to access this information.
> 
> I agree.
>>
>> Why not add change_mode for the acpi in order to enable or disable
>> the
>> events
> 
> thermal_zone_device_is_enabled() is invoked in acpi thermal driver
> because we only want to do thermal_zone_device_update() when the acpi
> thermal zone is enabled.
> 
> As thermal_zone_device_update() can handle a disabled thermal zone now,
> we can just remove the check.

Ah yes, good point!



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