[PATCH] thermal: Fix CPU mask truncation in power limit trace event

[PATCH] thermal: Fix CPU mask truncation in power limit trace event

[Hungyu Lin]

num_possible_cpus() counts CPUs, but CPU IDs need not be contiguous.
Using it to size the thermal_power_cpu_limit bitmap can omit CPUs with
higher IDs. For example, possible CPUs 0 and 64 produce an eight-byte
bitmap on a 64-bit system, dropping CPU 64.

Use nr_cpumask_bits for both sizing and copying the bitmap.

Fixes: 6828a4711f99 ("thermal: add trace events to the power allocator governor")
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
 drivers/thermal/thermal_trace.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/thermal_trace.h b/drivers/thermal/thermal_trace.h
index df8f4edd6068..2f953fd8289d 100644
--- a/drivers/thermal/thermal_trace.h
+++ b/drivers/thermal/thermal_trace.h
@@ -119,7 +119,7 @@ TRACE_EVENT(thermal_power_cpu_limit,
 	TP_ARGS(cpus, freq, cdev_state, power),
 
 	TP_STRUCT__entry(
-		__bitmask(cpumask, num_possible_cpus())
+		__bitmask(cpumask, nr_cpumask_bits)
 		__field(unsigned int,  freq      )
 		__field(unsigned long, cdev_state)
 		__field(u32,           power     )
@@ -127,7 +127,7 @@ TRACE_EVENT(thermal_power_cpu_limit,
 
 	TP_fast_assign(
 		__assign_bitmask(cpumask, cpumask_bits(cpus),
-				num_possible_cpus());
+				nr_cpumask_bits);
 		__entry->freq = freq;
 		__entry->cdev_state = cdev_state;
 		__entry->power = power;

base-commit: 503bb6e70bbf6304b8113373d09dfffcc4aa9183
-- 
2.43.0

Re: [PATCH] thermal: Fix CPU mask truncation in power limit trace event

[Rafael J. Wysocki (Intel)]

On Fri, Oct 23, 2026 at 8:08 AM Hungyu Lin <dennylin0707@gmail.com> wrote:
>
> num_possible_cpus() counts CPUs, but CPU IDs need not be contiguous.
> Using it to size the thermal_power_cpu_limit bitmap can omit CPUs with
> higher IDs. For example, possible CPUs 0 and 64 produce an eight-byte
> bitmap on a 64-bit system, dropping CPU 64.
>
> Use nr_cpumask_bits for both sizing and copying the bitmap.
>
> Fixes: 6828a4711f99 ("thermal: add trace events to the power allocator governor")
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
> ---
>  drivers/thermal/thermal_trace.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/thermal/thermal_trace.h b/drivers/thermal/thermal_trace.h
> index df8f4edd6068..2f953fd8289d 100644
> --- a/drivers/thermal/thermal_trace.h
> +++ b/drivers/thermal/thermal_trace.h
> @@ -119,7 +119,7 @@ TRACE_EVENT(thermal_power_cpu_limit,
>         TP_ARGS(cpus, freq, cdev_state, power),
>
>         TP_STRUCT__entry(
> -               __bitmask(cpumask, num_possible_cpus())
> +               __bitmask(cpumask, nr_cpumask_bits)
>                 __field(unsigned int,  freq      )
>                 __field(unsigned long, cdev_state)
>                 __field(u32,           power     )
> @@ -127,7 +127,7 @@ TRACE_EVENT(thermal_power_cpu_limit,
>
>         TP_fast_assign(
>                 __assign_bitmask(cpumask, cpumask_bits(cpus),
> -                               num_possible_cpus());
> +                               nr_cpumask_bits);
>                 __entry->freq = freq;
>                 __entry->cdev_state = cdev_state;
>                 __entry->power = power;
>
> base-commit: 503bb6e70bbf6304b8113373d09dfffcc4aa9183
> --

Applied as 7.4-rc material, thanks!