linux-kernel - Re: [PATCH v2 03/12] thermal: core: Represent suspend-related thermal zone flags as bits

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Message-ID: <3adbae5c-f6c2-4a9c-8544-7020b84a8845@arm.com>
Date: Mon, 21 Oct 2024 23:23:42 +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 03/12] thermal: core: Represent suspend-related thermal
 zone flags as bits



On 10/4/24 20:11, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Instead of using two separate fields in struct thermal_zone_device for
> representing flags related to thermal zone suspend, represent them
> explicitly as bits in one u8 "state" field.
> 
> Subsequently, that field will be used for addressing race conditions
> related to thermal zone initialization and exit.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> This is a new iteration of
> 
> https://lore.kernel.org/linux-pm/2215885.irdbgypaU6@rjwysocki.net/
> 
> v1 -> v2: The thermal zone guard has not been introduced yet, so adjust for that.
> 
> ---
>   drivers/thermal/thermal_core.c |   11 +++++------
>   drivers/thermal/thermal_core.h |   11 +++++++----
>   2 files changed, 12 insertions(+), 10 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -547,7 +547,7 @@ void __thermal_zone_device_update(struct
>   	int low = -INT_MAX, high = INT_MAX;
>   	int temp, ret;
>   
> -	if (tz->suspended || tz->mode != THERMAL_DEVICE_ENABLED)
> +	if (tz->state != TZ_STATE_READY || tz->mode != THERMAL_DEVICE_ENABLED)
>   		return;
>   
>   	ret = __thermal_zone_get_temp(tz, &temp);
> @@ -1662,7 +1662,7 @@ static void thermal_zone_device_resume(s
>   
>   	mutex_lock(&tz->lock);
>   
> -	tz->suspended = false;
> +	tz->state &= ~(TZ_STATE_FLAG_SUSPENDED | TZ_STATE_FLAG_RESUMING);

I see, we now clean both in on go...

>   
>   	thermal_debug_tz_resume(tz);
>   	thermal_zone_device_init(tz);
> @@ -1670,7 +1670,6 @@ static void thermal_zone_device_resume(s
>   	__thermal_zone_device_update(tz, THERMAL_TZ_RESUME);
>   
>   	complete(&tz->resume);
> -	tz->resuming = false;

so handled as well.

>   
>   	mutex_unlock(&tz->lock);
>   }
> @@ -1679,7 +1678,7 @@ static void thermal_zone_pm_prepare(stru
>   {
>   	mutex_lock(&tz->lock);
>   
> -	if (tz->resuming) {
> +	if (tz->state & TZ_STATE_FLAG_RESUMING) {
>   		/*
>   		 * thermal_zone_device_resume() queued up for this zone has not
>   		 * acquired the lock yet, so release it to let the function run
> @@ -1692,7 +1691,7 @@ static void thermal_zone_pm_prepare(stru
>   		mutex_lock(&tz->lock);
>   	}
>   
> -	tz->suspended = true;
> +	tz->state |= TZ_STATE_FLAG_SUSPENDED;
>   
>   	mutex_unlock(&tz->lock);
>   }
> @@ -1704,7 +1703,7 @@ static void thermal_zone_pm_complete(str
>   	cancel_delayed_work(&tz->poll_queue);
>   
>   	reinit_completion(&tz->resume);
> -	tz->resuming = true;
> +	tz->state |= TZ_STATE_FLAG_RESUMING;
>   
>   	/*
>   	 * Replace the work function with the resume one, which will restore the
> Index: linux-pm/drivers/thermal/thermal_core.h
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.h
> +++ linux-pm/drivers/thermal/thermal_core.h
> @@ -61,6 +61,11 @@ struct thermal_governor {
>   	struct list_head	governor_list;
>   };
>   
> +#define	TZ_STATE_FLAG_SUSPENDED	BIT(0)
> +#define	TZ_STATE_FLAG_RESUMING	BIT(1)
> +
> +#define TZ_STATE_READY		0
> +
>   /**
>    * struct thermal_zone_device - structure for a thermal zone
>    * @id:		unique id number for each thermal zone
> @@ -100,8 +105,7 @@ struct thermal_governor {
>    * @node:	node in thermal_tz_list (in thermal_core.c)
>    * @poll_queue:	delayed work for polling
>    * @notify_event: Last notification event
> - * @suspended: thermal zone suspend indicator
> - * @resuming:	indicates whether or not thermal zone resume is in progress
> + * @state: 	current state of the thermal zone
>    * @trips:	array of struct thermal_trip objects
>    */
>   struct thermal_zone_device {
> @@ -134,8 +138,7 @@ struct thermal_zone_device {
>   	struct list_head node;
>   	struct delayed_work poll_queue;
>   	enum thermal_notify_event notify_event;
> -	bool suspended;
> -	bool resuming;
> +	u8 state;
>   #ifdef CONFIG_THERMAL_DEBUGFS
>   	struct thermal_debugfs *debugfs;
>   #endif
> 
> 
> 

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