linux-kernel - Re: [PATCH v1] thermal: core: Fix the handling of invalid trip points

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Date: Fri, 17 May 2024 18:32:21 +0800
From: Wendy Wang <wendy.wang@...el.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
CC: Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>, Lukasz Luba <lukasz.luba@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>, Srinivas Pandruvada
	<srinivas.pandruvada@...ux.intel.com>, Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v1] thermal: core: Fix the handling of invalid trip points

Hi Rafael,

I have tested your patch '[PATCH v1] thermal: core: Fix the handling of invalid trip points'
on my server, which is running the v6.9 kernel, the thermal throttling test case has passed.

Tested-by: Wendy Wang <wendy.wang@...el.com>

On 2024-05-16 at 19:20:19 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Commit 9ad18043fb35 ("thermal: core: Send trip crossing notifications
> at init time if needed") overlooked the case when a trip point that
> has started as invalid is set to a valid temperature later.  Namely,
> the initial threshold value for all trips is zero, so if a previously
> invalid trip becomes valid and its (new) low temperature is above the
> zone temperature, a spurious trip crossing notification will occur and
> it may trigger the WARN_ON() in handle_thermal_trip().
> 
> To address this, set the initial threshold for all trips to INT_MAX.
> 
> There is also the case when a valid writable trip becomes invalid that
> requires special handling.  First, in accordance with the change
> mentioned above, the trip's threshold needs to be set to INT_MAX to
> avoid the same issue.  Second, if the trip in question is passive and
> it has been crossed by the thermal zone temperature on the way up, the
> zone's passive count has been incremented and it is in the passive
> polling mode, so its passive count needs to be adjusted to allow the
> passive polling to be turned off eventually.
> 
> Fixes: 9ad18043fb35 ("thermal: core: Send trip crossing notifications at init time if needed")
> Fixes: 042a3d80f118 ("thermal: core: Move passive polling management to the core")
> Reported-by: Zhang Rui <rui.zhang@...el.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/thermal/thermal_core.c |    9 ++++++++-
>  drivers/thermal/thermal_trip.c |   18 ++++++++++++++++++
>  2 files changed, 26 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/thermal/thermal_core.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_core.c
> +++ linux-pm/drivers/thermal/thermal_core.c
> @@ -1401,8 +1401,15 @@ thermal_zone_device_register_with_trips(
>  	tz->device.class = thermal_class;
>  	tz->devdata = devdata;
>  	tz->num_trips = num_trips;
> -	for_each_trip_desc(tz, td)
> +	for_each_trip_desc(tz, td) {
>  		td->trip = *trip++;
> +		/*
> +		 * Mark all thresholds as invalid to start with even though
> +		 * this only matters for the trips that start as invalid and
> +		 * become valid later.
> +		 */
> +		td->threshold = INT_MAX;
> +	}
>  
>  	thermal_set_delay_jiffies(&tz->passive_delay_jiffies, passive_delay);
>  	thermal_set_delay_jiffies(&tz->polling_delay_jiffies, polling_delay);
> Index: linux-pm/drivers/thermal/thermal_trip.c
> ===================================================================
> --- linux-pm.orig/drivers/thermal/thermal_trip.c
> +++ linux-pm/drivers/thermal/thermal_trip.c
> @@ -137,6 +137,24 @@ void thermal_zone_set_trip_temp(struct t
>  	if (trip->temperature == temp)
>  		return;
>  
> +	if (temp == THERMAL_TEMP_INVALID) {
> +		struct thermal_trip_desc *td = trip_to_trip_desc(trip);
> +
> +		if (trip->type == THERMAL_TRIP_PASSIVE &&
> +		    tz->temperature >= td->threshold) {
> +			/*
> +			 * The trip has been crossed, so the thermal zone's
> +			 * passive count needs to be adjusted.
> +			 */
> +			tz->passive--;
> +			WARN_ON_ONCE(tz->passive < 0);
> +		}
> +		/*
> +		 * Invalidate the threshold to avoid triggering a spurious
> +		 * trip crossing notification when the trip becomes valid.
> +		 */
> +		td->threshold = INT_MAX;
> +	}
>  	WRITE_ONCE(trip->temperature, temp);
>  	thermal_notify_tz_trip_change(tz, trip);
>  }
> 
> 
>