* [PATCH] trace/hwlat: Add WARN_ON in move_to_next_cpu()
@ 2025-08-11 8:01 Fushuai Wang
2025-08-14 19:06 ` Steven Rostedt
0 siblings, 1 reply; 2+ messages in thread
From: Fushuai Wang @ 2025-08-11 8:01 UTC (permalink / raw)
To: linux-trace-kernel, linux-kernel
Cc: rostedt, mhiramat, mathieu.desnoyers, Fushuai Wang
Add a WARN_ON check in move_to_next_cpu(). Next_cpu should
never be greater than or equal to nr_cpu_ids.
Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
---
kernel/trace/trace_hwlat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 2f7b94e98317..5024b0dcdbba 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -328,7 +328,7 @@ static void move_to_next_cpu(void)
next_cpu = cpumask_next_wrap(raw_smp_processor_id(), current_mask);
cpus_read_unlock();
- if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */
+ if (WARN_ON(next_cpu >= nr_cpu_ids)) /* Shouldn't happen! */
goto change_mode;
cpumask_clear(current_mask);
--
2.36.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] trace/hwlat: Add WARN_ON in move_to_next_cpu()
2025-08-11 8:01 [PATCH] trace/hwlat: Add WARN_ON in move_to_next_cpu() Fushuai Wang
@ 2025-08-14 19:06 ` Steven Rostedt
0 siblings, 0 replies; 2+ messages in thread
From: Steven Rostedt @ 2025-08-14 19:06 UTC (permalink / raw)
To: Fushuai Wang
Cc: linux-trace-kernel, linux-kernel, mhiramat, mathieu.desnoyers
On Mon, 11 Aug 2025 16:01:09 +0800
Fushuai Wang <wangfushuai@baidu.com> wrote:
> Add a WARN_ON check in move_to_next_cpu(). Next_cpu should
> never be greater than or equal to nr_cpu_ids.
>
> Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
> ---
> kernel/trace/trace_hwlat.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> index 2f7b94e98317..5024b0dcdbba 100644
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -328,7 +328,7 @@ static void move_to_next_cpu(void)
> next_cpu = cpumask_next_wrap(raw_smp_processor_id(), current_mask);
> cpus_read_unlock();
>
> - if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */
> + if (WARN_ON(next_cpu >= nr_cpu_ids)) /* Shouldn't happen! */
> goto change_mode;
Yeah, it shouldn't happen but it doesn't mean we need to add a WARN_ON().
It might even happen if user space is messing with the tracing_cpumask at
the same time. It shouldn't happen but it doesn't mean it will not happen.
We do not add WARN_ON() for things that could be trigger by user space.
-- Steve
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2025-08-11 8:01 [PATCH] trace/hwlat: Add WARN_ON in move_to_next_cpu() Fushuai Wang
2025-08-14 19:06 ` Steven Rostedt
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