Re: [PATCH -tip 22/32] sched: Split the cookie and setup per-task cookie on fork

[Joel Fernandes]

On Wed, Nov 25, 2020 at 12:07:09PM +0100, Peter Zijlstra wrote:
> On Tue, Nov 17, 2020 at 06:19:52PM -0500, Joel Fernandes (Google) wrote:
> > Also, for the per-task cookie, it will get weird if we use pointers of any
> > emphemeral objects. For this reason, introduce a refcounted object who's sole
> > purpose is to assign unique cookie value by way of the object's pointer.
> 
> Might be useful to explain why exactly none of the many pid_t's are
> good enough.

I thought about this already and it does not seem a good fit. When 2
processes share, it is possible that more processes are added to that logical
group. Then the original processes that share die, but if we hold on to the
pid_t or task_struct, that would be awkward. It seemed introducing a new
refcounted struct was the right way to go. I can add these details to the
change log.

thanks!

 - Joel