Re: [PATCH v2] sched/rt: Have RT_PUSH_IPI be default off for non PREEMPT_RT

[Steven Rostedt]

On Wed, 20 May 2026 08:09:04 -1000
Tejun Heo <tj@xxxxxxxxxx> wrote:

> On Wed, May 20, 2026 at 10:34:35PM +0530, Shrikanth Hegde wrote:
> > By any chance it is running with preempt=none/voluntary?
> > If so it might never call schedule until it goes back to user space.  
> 
> I think this might be it. In the production dump, the locked up cpus were
> often running btrfs compression / decompression. The kernel is PREEMPT_NONE
> and while that path has resched_curr()'s, with high enough irq frequency, it
> wouldn't be that difficult to catch the cpu enough times before it reaches
> the resched point.

But it should still be making forward progress. The IPI handler is very short.

Are the other CPUs running very short lived RT tasks that constantly
trigger the IPI push logic? I mean it would need to run a lot of RT
tasks that keep going to sleep to cause a IPI storm to trigger.

-- Steve