Re: [PATCH v5 1/3] sched: Use user_cpus_ptr for saving user provided cpumask in sched_setaffinity()

[Waiman Long]

On 8/17/22 04:28, Peter Zijlstra wrote:
> On Tue, Aug 16, 2022 at 03:27:32PM -0400, Waiman Long wrote:
>
> > This will be some changes in behavior for arm64 systems with asymmetric
> > CPUs in some corner cases. For instance, if sched_setaffinity()
> > has never been called and there is a cpuset change before
> > relax_compatible_cpus_allowed_ptr() is called, its subsequent call will
> > follow what the cpuset allows but not what the previous cpu affinity
> > setting allows.
> That's arguably a correctness fix, no? That is, the save/restore should
> not have been allowed to revert to an earlier cpuset state.

Yes, it is a correctness fix in a sense. I just want to highlight that 
there will be some slight changes in behavior in some corner cases for 
the arm64 arch.

Cheers,
Longman