Re: [PATCH v2 6/6] sched: warn for high latency with TIF_NEED_RESCHED_LAZY

[Sebastian Andrzej Siewior]

On 2024-11-06 12:17:58 [-0800], Ankur Arora wrote:
> Add support for warning if the TIF_NEED_RESCHED_LAZY bit is set
> without rescheduling for more than the latency_warn_ms period.

You fail to explain _why_ it is required to also check
TIF_NEED_RESCHED_LAZY to not be set.

The problem with NEED_RESCHED set but no scheduling in 100ms is a long
preempt-off or IRQ-off region .
The problem with NEED_RESCHED_LAZY set but no scheduling in 100ms is a
missing timer tick in that time. Also the previous mentioned things
might have happen.
And the code acting on NEED_RESCHED_LAZY is invoked before this check
is.

Sebastian