Re: [PATCH 0/4] sched: Various reweight_entity() fixes

[Peter Zijlstra]

On Thu, Feb 12, 2026 at 06:16:11PM +0100, Peter Zijlstra wrote:
> On Thu, Feb 12, 2026 at 12:59:43PM +0100, Peter Zijlstra wrote:
> > On Thu, Feb 12, 2026 at 01:13:30PM +0530, K Prateek Nayak wrote:
> 
> > >     Enqueue cfs_rq: depth(1) weight(2144337920) nr_queued(2045) sum_w_vruntime(18343811230990336)    sum_weight(2144337920) zero_vruntime(18337852274) sum_shift(0) avg_vruntime(18337852274)
> > >     Dequeue cfs_rq: depth(1) weight(2144337920) nr_queued(2045) sum_w_vruntime(1303379968)           sum_weight(2143289344) zero_vruntime(18354971669) sum_shift(0) avg_vruntime(18354971669)
> 
> After staring at waaay too many traces of my own, which confirm what
> you're seeing, but didn't want to make any sense either...
> 
> ... I thinks I found it ...
> 
> Note that sum_weight, that has _just_ flipped bit 31 and thus turned
> negative *if* it were a 32bit number. Every time, exactly at this point
> things started to go sideways.
> 
> So I went looking for where this might be and I found the below.
> 
> My latest run has passed 0x8000000/(1024*1024) = 2048 tasks and is still
> running. Numbers are still sane, fingers crossed.
> 

I made it all the way to 3k tasks on the one CPU and all is well.