[PATCH 4/5] ARM: Disable jump-label on PREEMPT_RT.

[Steven Rostedt]

On Thu, 30 Oct 2025 10:56:15 +0100
Sebastian Andrzej Siewior <bigeasy at linutronix.de> wrote:

> trace events were an example and this is used to enable tracing in
> production or development to gather information if something is not
> working right _or_ on the edge to investigate. A latency spike at this
> point would be a timing violation forcing the system into a safe state
> an so not allowing further investigations.
> 
> I hope I made it clear that using jump-labels at this point is not
> doable at this point and a warning does not improve things. Improving
> the implementation on ARM as it has been done on ARM64 or X86 is how I
> would compare the situation to printk. Not adding a warning at boot
> time.

I wasn't talking about the print being at boot time. But when it gets
enabled (like when RT throttling happened). I wouldn't even do it the first
time it gets enabled, but print a waring when it is activated if the last
time it printed a warning was over a minute ago. Thus, even if it was
already printed, but it didn't cause any noticeable latency, it would print
again when it does.

Thus, if the system goes into a "safe state", it is obvious from the logs
it was caused by a user interaction.

-- Steve