Re: [PATCH] tasks: Extract rcu_users out of union

Oleg Nesterov
2023-02-17T10:26:23Z

On 02/16, David Vernet wrote:
>
> On Thu, Feb 16, 2023 at 09:04:59AM +0100, Oleg Nesterov wrote:
> >
> > > a task that's successfully looked
> > > up in e.g. the pid_list with find_task_by_pid_ns(), can always have a
> > > 'usage' reference acquired on them, as it's guaranteed to be >
> > > 0 until after the next gp.
> >
> > Yes. So it seems you need another key-to-task_struct map with rcu-safe
> > lookup/get and thus the add() method needs inc_not_zero(task->rcu_users) ?
>
> Yes, exactly.

OK, in this case I agree, inc_not_zero(rcu_users) makes sense and thus we need
this patch.

Just I was confused by the previous part of the changelog due to my bad English.

Thanks,

Oleg.