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

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Date:   Thu, 2 Jul 2020 19:52:19 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     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>,
        Zhang Rui <rui.zhang@...el.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 02/07/2020 19:49, Daniel Lezcano wrote:

[ ... ]

>> Thanks!
>>
>> That confirms your suspicions.
>>
>> 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.
> 
> Why not add change_mode for the acpi in order to enable or disable the
> events and for imx_thermal use irq_enabled flag instead of the thermal
> zone mode? Moreover it is very unclear why this function is needed in
> imx_get_temp(), and I suspect we should be able to get rid of it.

If you agree with that you can send a patch on top of your series so I
can test it fixes the imx platform.


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