On Tue, Dec 21, 2021 at 05:19:00PM +0000, Peter Oskolkov wrote:
> On Tue, Dec 14, 2021 at 09:44:48PM +0100, Peter Zijlstra wrote:
> > +static struct task_struct *umcg_get_task(u32 tid)
> > +{
> > + struct task_struct *tsk = NULL;
> > +
> > + if (tid) {
> > + rcu_read_lock();
> > + tsk = find_task_by_vpid(tid);
> > + if (tsk && current->mm == tsk->mm && tsk->umcg_task)
>
> This essentially limits all operations to a single mm/process.
> Fine for now, but a fast remote context switch is also a valid use
> case. It is not directly related to userspace scheduling, so I'm
> just mentioning it here. Maybe server-to-server cross-process
> context switches should be allowed for the same user/cgroup? (Again,
> this is for later to consider).
Doing cross-address-space UMCG will be a massive effort, too much
(pretty much everything) in this implementation assumes things are
directly addressable.
> > + get_task_struct(tsk);
> > + else
> > + tsk = NULL;
> > + rcu_read_unlock();
> > + }
> > +
> > + return tsk;
> > +}
