linux-kernel - Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to

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Message-ID: <68ed6185-a602-c0fc-721e-b5d68fea83f8@huawei.com>
Date: Wed, 21 Aug 2024 16:49:52 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM
	<linux-pm@...r.kernel.org>
CC: LKML <linux-kernel@...r.kernel.org>, Daniel Lezcano
	<daniel.lezcano@...aro.org>, Lukasz Luba <lukasz.luba@....com>, Zhang Rui
	<rui.zhang@...el.com>
Subject: Re: [PATCH v3 02/14] thermal: core: Rearrange checks in
 thermal_bind_cdev_to_trip()


在 2024/8/19 23:51, Rafael J. Wysocki 写道:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> It is not necessary to look up the thermal zone and the cooling device
> in the respective global lists to check whether or not they are
> registered.  It is sufficient to check whether or not their respective
> list nodes are empty for this purpose.
>
> Use the above observation to simplify thermal_bind_cdev_to_trip().  In
> addition, eliminate an unnecessary ternary operator from it.
>
> Moreover, add lockdep_assert_held() for thermal_list_lock to it because
> that lock must be held by its callers when it is running.
>
> No intentional functional impact.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> v1 -> v3: No changes
>
> ---
>   drivers/thermal/thermal_core.c |   16 ++++------------
>   1 file changed, 4 insertions(+), 12 deletions(-)
>
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -781,25 +781,17 @@ int thermal_bind_cdev_to_trip(struct the
>   {
>   	struct thermal_instance *dev;
>   	struct thermal_instance *pos;
> -	struct thermal_zone_device *pos1;
> -	struct thermal_cooling_device *pos2;
>   	bool upper_no_limit;
>   	int result;
>   
> -	list_for_each_entry(pos1, &thermal_tz_list, node) {
> -		if (pos1 == tz)
> -			break;
> -	}
> -	list_for_each_entry(pos2, &thermal_cdev_list, node) {
> -		if (pos2 == cdev)
> -			break;
> -	}
> +	lockdep_assert_held(&thermal_list_lock);
>   
> -	if (tz != pos1 || cdev != pos2)
> +	if (list_empty(&tz->node) || list_empty(&cdev->node))
The old verification is ensure that tz and cdev already add to 
thermal_tz_list and thermal_cdev_list，respectively.
Namely, tz and cdev are definitely registered and intialized.
The check is ok for all untizalized thermal_zone_device and cooling device.
But the new verification doesn't seem to do that.
>   		return -EINVAL;
>   
>   	/* lower default 0, upper default max_state */
> -	lower = lower == THERMAL_NO_LIMIT ? 0 : lower;
> +	if (lower == THERMAL_NO_LIMIT)
> +		lower = 0;
>   
>   	if (upper == THERMAL_NO_LIMIT) {
>   		upper = cdev->max_state;
>
>
>
>
> .