linux-kernel - Re: [PATCH v2 05/11] thermal: core: Call thermal_governor_update

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Message-ID: <ea44a43b-a02f-47ca-8143-38ae21f476be@arm.com>
Date: Tue, 22 Oct 2024 22:10:56 +0100
From: Lukasz Luba <lukasz.luba@....com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux PM <linux-pm@...r.kernel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: Re: [PATCH v2 05/11] thermal: core: Call thermal_governor_update_tz()
 outside of cdev lock



On 10/10/24 23:12, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Holding a cooling device lock under thermal_governor_update_tz() is not
> necessary and it may cause lockdep to complain if any governor's
> .update_tz() callback attempts to lock a cdev.
> 
> For this reason, move the thermal_governor_update_tz() calls in
> thermal_bind_cdev_to_trip() and thermal_unbind_cdev_from_trip() from
> under the cdev lock.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> This is a resend of
> 
> https://lore.kernel.org/linux-pm/1921484.CQOukoFCf9@rjwysocki.net/
> 
> ---
>   drivers/thermal/thermal_core.c |   11 +++++------
>   1 file changed, 5 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -832,13 +832,13 @@ static int thermal_bind_cdev_to_trip(str
>   	if (!result) {
>   		list_add_tail(&dev->trip_node, &td->thermal_instances);
>   		list_add_tail(&dev->cdev_node, &cdev->thermal_instances);
> -
> -		thermal_governor_update_tz(tz, THERMAL_TZ_BIND_CDEV);
>   	}
>   	mutex_unlock(&cdev->lock);
>   
> -	if (!result)
> +	if (!result) {
> +		thermal_governor_update_tz(tz, THERMAL_TZ_BIND_CDEV);
>   		return 0;
> +	}
>   
>   	device_remove_file(&tz->device, &dev->weight_attr);
>   remove_trip_file:
> @@ -873,9 +873,6 @@ static void thermal_unbind_cdev_from_tri
>   		if (pos->cdev == cdev) {
>   			list_del(&pos->trip_node);
>   			list_del(&pos->cdev_node);
> -
> -			thermal_governor_update_tz(tz, THERMAL_TZ_UNBIND_CDEV);
> -
>   			mutex_unlock(&cdev->lock);
>   			goto unbind;
>   		}
> @@ -885,6 +882,8 @@ static void thermal_unbind_cdev_from_tri
>   	return;
>   
>   unbind:
> +	thermal_governor_update_tz(tz, THERMAL_TZ_UNBIND_CDEV);
> +
>   	device_remove_file(&tz->device, &pos->weight_attr);
>   	device_remove_file(&tz->device, &pos->attr);
>   	sysfs_remove_link(&tz->device.kobj, pos->name);
> 
> 
> 

Reviewed-by: Lukasz Luba <lukasz.luba@....com>