Re: [PATCH v2 1/7] sched/fair: Fix zero_vruntime tracking

[K Prateek Nayak]

Hello Peter,

On 3/30/2026 8:10 PM, Peter Zijlstra wrote:
> On Mon, Mar 30, 2026 at 08:07:06PM +0530, K Prateek Nayak wrote:
>> Hello Peter,
>>
>> On 3/30/2026 3:40 PM, Peter Zijlstra wrote:
>>> This means, that if the two tasks playing leapfrog can reach the
>>> critical speed to reach the overflow point inside one tick's worth of
>>> time, we're up a creek.
>>>
>>> If this is indeed the case, then the below should cure things.
>>
>> I have been running with this for four hours now and haven't seen
>> any splats or crashes on my setup. I could reliably trigger the
>> warning from __sum_w_vruntime_add() within an hour previously so
>> it is safe to say I was hitting exactly this.
>>
>> Feel free to include:
>>
>> Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> 
> Ha!, excellent. Thanks!

Turns out I spoke too soon and it did eventually run into that
problem again and then eventually crashed in pick_task_fair()
later so there is definitely something amiss still :-(

I'll throw in some debug traces and get back tomorrow.

-- 
Thanks and Regards,
Prateek