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

[David Vernet]

On Fri, Feb 17, 2023 at 11:25:21AM +0100, Oleg Nesterov wrote:
> 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.

Thanks again for taking a look.

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

No worries at all -- the commit summary definitely could have been more
clear.

Does anyone else have any thoughts? Is there anything else we need to do
for this patch to land?

Thanks,
David