Re: [RFC PATCH] sched: Do not copy user_cpus_ptr when parent is reset_on_fork

[Waiman Long]

On 9/5/24 09:12, Phil Auld wrote:
> On Thu, Sep 05, 2024 at 08:42:33AM -0400 Waiman Long wrote:
> > On 9/5/24 05:04, Xuewen Yan wrote:
> > > Now, the task's user_cpus_ptr would dup from parent's user_cpus_ptr.
> > > It is better reset the user_cpus_ptr when parent's reset_on_fork
> > > is set.
> > According to sched(7):
> >
> >         Each thread has a reset-on-fork scheduling flag.  When this flag
> >         is set, children created by fork(2) do not inherit privileged
> >         scheduling policies.
> >
> > It can be argued what are considered privileged scheduling policies. AFAICS,
> > a restricted affinity doesn't seem to be a "privileged" scheduling policy.
> > That is my own opinion strictly from the definition point of view, I will
> > let others weigh in on that and I am OK to go either way.
> I think that one could argue that clearing a restricted affinity is
> increasing the privilege and not preventing inheritence of same.
> i.e. it would be the opposite of what reset-on-fork means.
>
> I'd say NAK to this one if I had that power.

Maybe I am not clear enough in my previous mail. My position is the same 
as yours. I think this patch is not necessary. More reasons should be 
provided as to why it is right to not inherited the restricted affinity 
when reset-on-fork flag is reset.

Cheers,
Longman