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

From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Zhang Rui <rui.zhang@intel.com>,
	Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
	linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org,
	netdev@vger.kernel.org, linux-wireless@vger.kernel.org,
	platform-driver-x86@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	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>,
	"Niklas Söderlund" <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
Subject: Re: [PATCH v7 00/11] Stop monitoring disabled devices
Date: Fri, 3 Jul 2020 08:38:48 +0200	[thread overview]
Message-ID: <58265668-fc6d-729a-c126-0c73c2ea853b@linaro.org> (raw)
In-Reply-To: <44c622dd7de8c7bf143c4435c0edd1b98d09a3d6.camel@intel.com>

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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