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Subject: Re: [PATCH v7 00/11] Stop monitoring disabled devices
To:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Zhang Rui <rui.zhang@intel.com>, linux-pm@vger.kernel.org,
        linux-acpi@vger.kernel.org, netdev@vger.kernel.org,
        linux-wireless@vger.kernel.org,
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        linux-renesas-soc@vger.kernel.org,
        linux-rockchip@lists.infradead.org
Cc:     "Rafael J . Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Vishal Kulkarni <vishal@chelsio.com>,
        "David S . Miller" <davem@davemloft.net>,
        Jiri Pirko <jiri@mellanox.com>,
        Ido Schimmel <idosch@mellanox.com>,
        Johannes Berg <johannes.berg@intel.com>,
        Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
        Luca Coelho <luciano.coelho@intel.com>,
        Intel Linux Wireless <linuxwifi@intel.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        Peter Kaestle <peter@piie.net>,
        Darren Hart <dvhart@infradead.org>,
        Andy Shevchenko <andy@infradead.org>,
        Sebastian Reichel <sre@kernel.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Amit Kucheria <amit.kucheria@verdurent.com>,
        Support Opensource <support.opensource@diasemi.com>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        =?UTF-8?Q?Niklas_S=c3=b6derlund?= <niklas.soderlund@ragnatech.se>,
        Heiko Stuebner <heiko@sntech.de>,
        Orson Zhai <orsonzhai@gmail.com>,
        Baolin Wang <baolin.wang7@gmail.com>,
        Chunyan Zhang <zhang.lyra@gmail.com>,
        Allison Randal <allison@lohutok.net>,
        Enrico Weigelt <info@metux.net>,
        Gayatri Kammela <gayatri.kammela@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        kernel@collabora.com
References: <20200629122925.21729-1-andrzej.p@collabora.com>
 <aab40d90-3f72-657c-5e14-e53a34c4b420@linaro.org>
 <3d03d1a2-ac06-b69b-93cb-e0203be62c10@collabora.com>
 <47111821-d691-e71d-d740-e4325e290fa4@linaro.org>
 <be9b7ee3-cad0-e462-126d-08de9b226285@collabora.com>
 <4353a939-3f5e-8369-5bc0-ad8162b5ffc7@linaro.org>
 <a531d80f-afd1-2dec-6c77-ed984e97595c@collabora.com>
 <db1ff4e1-cbf8-89b3-5d64-b91a1fd88a41@linaro.org>
 <73942aea-ae79-753c-fe90-d4a99423d548@collabora.com>
 <374dddd9-b600-3a30-d6c3-8cfcefc944d9@linaro.org>
 <5a28deb7-f307-8b03-faad-ab05cb8095d1@collabora.com>
 <8aeb4f51-1813-63c1-165b-06640af5968f@linaro.org>
 <685ef627-e377-bbf1-da11-7f7556ca2dd7@collabora.com>
 <d41bf28f-ee91-6946-2334-f11ec81f96fe@linaro.org>
 <44c622dd7de8c7bf143c4435c0edd1b98d09a3d6.camel@intel.com>
 <58265668-fc6d-729a-c126-0c73c2ea853b@linaro.org>
From:   Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Message-ID: <625911aa-a55f-dcbf-66b3-719117c6aa32@collabora.com>
Date:   Fri, 3 Jul 2020 12:45:44 +0200
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Hi,

W dniu 03.07.2020 o 08:38, Daniel Lezcano pisze:
> 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!
> 
> 
> 

I sent a short series with fixes. Daniel, can you kindly test it?

Regards,

Andrzej