linux-kernel - Re: [PATCH v2 05/12] thermal: core: Fix race between zone registration and system suspend

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Message-ID: <8556b1b6-e557-46db-bcc0-a2c542b7ed2c@arm.com>
Date: Mon, 21 Oct 2024 23:27:56 +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 05/12] thermal: core: Fix race between zone
 registration and system suspend



On 10/4/24 20:19, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> If the registration of a thermal zone takes place at the time when
> system suspend is started, thermal_pm_notify() can run before the new
> thermal zone is added to thermal_tz_list and its "suspended" flag will
> not be set.  Consequently, if __thermal_zone_device_update() is called
> for that thermal zone, it will not return early as expected which may
> cause some destructive interference with the system suspend or resume
> flow to occur.
> 
> To avoid that, make thermal_zone_init_complete() introduced previously
> set the "suspended" flag for new thermal zones if it runs during system
> suspend or resume.
> 
> Fixes: 4e814173a8c4 ("thermal: core: Fix thermal zone suspend-resume synchronization")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> This is a new iteration of
> 
> https://lore.kernel.org/linux-pm/3335807.44csPzL39Z@rjwysocki.net/
> 
> v1 -> v2: Rebase and add a fixes tag.
> 
> ---
>   drivers/thermal/thermal_core.c |   18 ++++++++++++++++--
>   1 file changed, 16 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -40,6 +40,8 @@ static DEFINE_MUTEX(thermal_governor_loc
>   
>   static struct thermal_governor *def_governor;
>   
> +static bool thermal_pm_suspended;
> +
>   /*
>    * Governor section: set of functions to handle thermal governors
>    *
> @@ -1337,6 +1339,14 @@ static void thermal_zone_init_complete(s
>   	mutex_lock(&tz->lock);
>   
>   	tz->state &= ~TZ_STATE_FLAG_INIT;
> +	/*
> +	 * If system suspend or resume is in progress at this point, the
> +	 * new thermal zone needs to be marked as suspended because
> +	 * thermal_pm_notify() has run already.
> +	 */
> +	if (thermal_pm_suspended)
> +		tz->state |= TZ_STATE_FLAG_SUSPENDED;
> +
>   	__thermal_zone_device_update(tz, THERMAL_EVENT_UNSPECIFIED);
>   
>   	mutex_unlock(&tz->lock);
> @@ -1514,10 +1524,10 @@ thermal_zone_device_register_with_trips(
>   	list_for_each_entry(cdev, &thermal_cdev_list, node)
>   		thermal_zone_cdev_bind(tz, cdev);
>   
> -	mutex_unlock(&thermal_list_lock);
> -
>   	thermal_zone_init_complete(tz);
>   
> +	mutex_unlock(&thermal_list_lock);
> +
>   	thermal_notify_tz_create(tz);
>   
>   	thermal_debug_tz_add(tz);
> @@ -1737,6 +1747,8 @@ static int thermal_pm_notify(struct noti
>   	case PM_SUSPEND_PREPARE:
>   		mutex_lock(&thermal_list_lock);
>   
> +		thermal_pm_suspended = true;
> +
>   		list_for_each_entry(tz, &thermal_tz_list, node)
>   			thermal_zone_pm_prepare(tz);
>   
> @@ -1747,6 +1759,8 @@ static int thermal_pm_notify(struct noti
>   	case PM_POST_SUSPEND:
>   		mutex_lock(&thermal_list_lock);
>   
> +		thermal_pm_suspended = false;
> +
>   		list_for_each_entry(tz, &thermal_tz_list, node)
>   			thermal_zone_pm_complete(tz);
>   
> 
> 
> 

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