Re: uprobe splat in PREEMP_RT

Oleg Nesterov
2025-04-03T12:28:45Z

On 04/03, Sebastian Sewior wrote:
>
> On 2025-04-02 16:12:46 [+0200], Oleg Nesterov wrote:
> > >
> > > Yes. This would work for here just to skip the check because of all
> > > details that are hard to express. Therefore I suggested to use
> > > raw_write_seqcount_begin() instead of write_seqcount_begin() in
> > > 20250402122158.j_8VoHQ-@linutronix.de. Would that work?
> >
> > If this can work, then let me repeat: why can't we turn ->ri_seqcount
> > into a boolean?
>
> I just stumbled here due to the warning. Now that you ask the question,
> it is used a bool in the current construct. So yes, I also don't see
> why.

Well, Andrii has already explained why he decided to abuse seqcount_t,
to avoid the explicti barriers in this code... I won't argue.

So, just in case, I agree that your suggestion to use
raw_write_seqcount_begin/end should obviously fix the problem.

Oleg.