[PATCH] kernel/sys: Optimize do_prlimit lock scope to reduce contention

[Oleg Nesterov]

On 11/28, Oleg Nesterov wrote:
>
> On 11/28, Oleg Nesterov wrote:
> >
> > The problem is that task_lock(tsk->group_leader) doesn't look right with or
> > without this patch. I'll try to make a fix on weekend.
> >
> > If the caller is sys_prlimit64() and tsk != current, then ->group_leader is
> > not stable, do_prlimit() can race with mt exec and take the wrong lock.
>
> ... and task_unlock(tsk->group_leader) is simply unsafe.
>
> perhaps something like below,

No, this is wrong too,

> I'll try to think more.

Yes...

Oleg.