On 2020-11-03 12:37:49 [+0100], Oleg Nesterov wrote:
> On 11/02, Sebastian Andrzej Siewior wrote:
> >
> > On 2020-11-02 16:50:01 [+0100], Oleg Nesterov wrote:
> > >
> > > static void ptrace_unfreeze_traced(struct task_struct *task)
> > > {
> > > - if (task->state != __TASK_TRACED)
> > > - return;
> > > + bool frozen = true;
> >
> > Is this okay for !PREEMPT_RT or is this considered as an important
> > fast-path on !PREEMPT_RT?
>
> I do not know how can ptrace_unfreeze_traced() check both ->state and
> ->saved_state lockless.
>
> If it is possible then task_is_traced() can avoid pi_lock too?
Now we can't. That lock is the only thing that guarantees consistent
state.
> OK, I'll send V2 in a minute.
>
> > This `saved_state' is only used for RT so it might make sense to avoid
> > the PI-lock on non-RT.
>
> The same is true for ptrace_freeze_traced(), we can probably add ifdef's
> but I am not sure this makes sense...
Okay. Then we keep it as it for now.
> Oleg.
Sebastian
