Re: [PATCH v2 4/4] rv/rtapp: Add wakeup monitor

[Chao Liu]

Hi Nam,

I've been looking into the RV subsystem, and while reading this patch
I noticed a small inconsistency.

On Fri, Jun 19, 2026 at 09:21:22AM +0800, Nam Cao wrote:
> Add a wakeup monitor to detect a lower-priority task waking up a
> higher-priority task.
> 
> The rtapp/sleep monitor already detects this. However, that monitor
> triggers an error in the context of the wakee task and user only gets
> the stacktrace of that task. It is also extremely useful to get the
> stacktrace of the waker task, which this monitor offers. In other
> words, this monitor complements the rtapp/sleep monitor.
> 
> Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
> ---

[...]

> +Monitor wakeup
> +++++++++++++++
> +
> +The `wakeup` monitor reports real-time threads being woken by lower-priority threads,
> +which is a hint of priority inversion. Its specification is::
> +
> +  RULE = always (((RT and USER_THREAD) imply
> +                (not (WOKEN_BY_LOWER_PRIO or WOKEN_BY_SOFTIRQ)) or ALLOWLIST))
> +
> +  ALLOWLIST = BLOCK_ON_RT_MUTEX
> +           or FUTEX_LOCK_PI
> +

[...]

> +static void handle_sched_waking(void *data, struct task_struct *task)
> +{
> +	if (in_task()) {
> +		if (current->prio > task->prio)
> +			ltl_atom_pulse(task, LTL_WOKEN_BY_LOWER_PRIO, true);

The implementation also reports wakeups from softirq context through
WOKEN_BY_SOFTIRQ:

> +	} else if (in_serving_softirq()) {
> +		ltl_atom_pulse(task, LTL_WOKEN_BY_SOFTIRQ, true);
> +	}

Should this description mention softirq wakeups as well?

The Kconfig help text, struct rv_monitor's .description, and
MODULE_DESCRIPTION() seem to have the same omission.

I also have a small follow-up documentation patch based on this series,
which I plan to send as an RFC shortly.

Thanks,
Chao