Re: [PATCHSET v2 sched_ext/for-7.3] sched_ext: Follow-up fixes and missing cap enforcement

[Andrea Righi]

Hi Tejun,

On Fri, Jul 24, 2026 at 09:16:46AM -1000, Tejun Heo wrote:
> Hello,
> 
> Follow-up fixes and enforcement holes plugged from the recent
> sub-scheduler work. The first patch fixes the tools' restart loop
> clobbering an exit that was requested while a restart was pending.
> 
> The rest tighten how cid-addressed operations from sub-schedulers are
> handled when the caller lacks the necessary caps. Reenq to another
> sched's local DSQs is now denied and counted, and a new event counts
> the already-denied kicks. These checks are lockless - transient false
> positives from cap rotation are harmless and false negatives can't
> happen by visibility. cpuperf control moves behind a new SCX_CAP_PERF
> which only the root holds by default, and scx_bpf_cidperf_set() reports
> the result synchronously as its check is authoritative under the
> target's rq lock.

I haven’t found any issues in this series, everything looks good to me.

Reviewed-by: Andrea Righi <arighi@xxxxxxxxxx>

Thanks,
-Andrea

> 
> v2: - Kernel-doc comment moved to scx_bpf_cpuperf_set() instead of being
>       left attached to the factored-out helper (0004, reported by
>       sashiko).
>     - The versioned scx_bpf_cidperf_set___v2() interface and the tools
>       compat wrapper are dropped. The cid-form interface is still under
>       initial development, so the signature is changed in place to
>       return s32 (0005).
> 
> v1: https://lore.kernel.org/r/20260724182125.985061-1-tj@xxxxxxxxxx
> 
>  0001-tools-sched_ext-Don-t-restart-over-a-pending-exit-re.patch
>  0002-sched_ext-Gate-local-DSQ-reenq-on-baseline-cid-acces.patch
>  0003-sched_ext-Count-kicks-denied-for-lacking-baseline-ci.patch
>  0004-sched_ext-Factor-out-scx_cpuperf_set.patch
>  0005-sched_ext-Gate-scx_bpf_cidperf_set-behind-a-new-SCX_.patch
> 
> Based on sched_ext/for-7.3 (c509d8107026).
> 
> The patches are also available in the following git branch:
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-sub-cap-gates-v2
> 
> diffstat follows. Thanks.
> 
>  kernel/sched/ext/ext.c                   | 139 +++++++++++++++++++++----------
>  kernel/sched/ext/internal.h              |  31 ++++++-
>  tools/sched_ext/include/scx/common.bpf.h |   2 +-
>  tools/sched_ext/scx_central.c            |   2 +-
>  tools/sched_ext/scx_cpu0.c               |   2 +-
>  tools/sched_ext/scx_flatcg.c             |   2 +-
>  tools/sched_ext/scx_pair.c               |   2 +-
>  tools/sched_ext/scx_qmap.bpf.c           |  17 ++--
>  tools/sched_ext/scx_qmap.c               |   2 +-
>  tools/sched_ext/scx_sdt.c                |   2 +-
>  tools/sched_ext/scx_simple.c             |   2 +-
>  tools/sched_ext/scx_userland.c           |  11 +--
>  12 files changed, 149 insertions(+), 65 deletions(-)
> 
> --
> tejun