Re: [PATCH sched/core] sched/rt: Fix RT_PUSH_IPI soft lockup loop

[Tejun Heo <tj@kernel.org>]

Hello,

On Wed, May 13, 2026 at 09:31:08PM -0400, Steven Rostedt wrote:
> OK, this is what I was missing. The fact that the CPU was running a
> softirq at the time that was running for a very long time that prevents
> the schedule from happening.

Right, although, in prod case, I don't think each softirq invocation is that
long. It's maybe a few msecs, if that. However, there's a constant stream of
them and if you slow down the CPU enough with IPIs, the CPU can't ever clear
pending softirq although it only runs a short time each time it enters
softirq.

> So if the current task running is SCHED_OTHER we still need to handle
> the case where the next task is pinned, as it will cause a warning
> again if it tries to move the fair task, especially since that doesn't
> fix the overloading.
> 
> I think this requires a bit more complex fix. Perhaps if the current
> task is fair and the next task is pinned, it needs to look for the task
> after that one to move.

I see. You know the code and history a lot better than I do. Wanna take
over?

Thanks.

-- 
tejun