Re: [patch V5 00/20] sched: Rewrite MM CID management

[Peter Zijlstra]

On Tue, Jan 27, 2026 at 04:01:11PM -0800, Ihor Solodrai wrote:
> On 11/19/25 9:26 AM, Thomas Gleixner wrote:
> > This is a follow up on the V4 series which can be found here:
> > 
> >     https://lore.kernel.org/20251104075053.700034556@xxxxxxxxxxxxx
> > 
> > The V1 cover letter contains a detailed analyisis of the issues:
> > 
> >     https://lore.kernel.org/20251015164952.694882104@xxxxxxxxxxxxx
> > 
> > TLDR: The CID management is way to complex and adds significant overhead
> > into scheduler hotpaths.
> > 
> > The series rewrites MM CID management in a more simplistic way which
> > focusses on low overhead in the scheduler while maintaining per task CIDs
> > as long as the number of threads is not exceeding the number of possible
> > CPUs.
> 
> Hello Thomas, everyone.
> 
> BPF CI caught a deadlock on current bpf-next tip (35538dba51b4).
> Job: https://github.com/kernel-patches/bpf/actions/runs/21417415035/job/61670254640
> 
> It appears to be related to this series. Pasting a splat below.
> 
> Any ideas what might be going on?

That splat is only CPU2, that's not typically very useful in a lockup
scenario.