linux-kernel - Re: [PATCH 2/4] thermal/drivers/exynos: fix set_trip

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Message-ID: <Y5nhpfAislGiIQOU@hovoldconsulting.com>
Date:   Wed, 14 Dec 2022 15:45:57 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Johan Hovold <johan+linaro@...nel.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Amit Kucheria <amitk@...nel.org>,
        Thara Gopinath <thara.gopinath@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        linux-pm@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 2/4] thermal/drivers/exynos: fix set_trip_temp() deadlock

On Wed, Dec 14, 2022 at 02:16:15PM +0100, Johan Hovold wrote:
> The set_trip_temp() callback is used when changing the trip temperature
> through sysfs. As it is called with the thermal-zone-device lock held
> it must not use thermal_zone_get_trip() directly or it will deadlock.
> 
> Fixes: 169865e317f2 ("thermal/drivers/exynos: Use generic thermal_zone_get_trip() function")
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/thermal/samsung/exynos_tmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
> index 37465af59262..cf9028f80415 100644
> --- a/drivers/thermal/samsung/exynos_tmu.c
> +++ b/drivers/thermal/samsung/exynos_tmu.c
> @@ -354,7 +354,7 @@ static void exynos4210_tmu_set_trip_temp(struct exynos_tmu_data *data,
>  	struct thermal_trip trip;
>  	u8 ref, th_code;
>  
> -	if (thermal_zone_get_trip(data->tzd, 0, &trip))
> +	if (__thermal_zone_get_trip(data->tzd, 0, &trip))
>  		return;
>  
>  	ref = trip.temperature / MCELSIUS;

As Daniel noted, this patch is not correct as this function is not
actually a thermal_zone_device_ops::set_trip_temp callback.

Please drop this one.

Johan