Re: [PATCH v2 4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing outside task context

[Yosry Ahmed <yosryahmed@google.com>]

On Thu, Mar 30, 2023 at 1:15 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Thu 30-03-23 01:06:26, Yosry Ahmed wrote:
> [...]
> > If we achieve that, do you think it makes sense to add
> > WARN_ON_ONCE(irqs_disabled()) instead to prevent future users from
> > flushing while disabling irqs or in irq context?
>
> WARN_ON (similar to BUG_ON) will not prevent anybody from doing bad
> things. We already have means to shout about sleepable code being
> invoked from an atomic context and there is no reason to duplicate that.
> As I've said earlier WARN_ON might panic the system in some
> configurations (and yes they are used also in production systems - do
> not ask me why...). So please be careful about that and use that only
> when something really bad (yet recoverable) is going on.

Thanks for the information (I was about to ask why about production
systems, but okay..). I will avoid WARN_ON completely. For the
purposes of this series I will drop this patch anyway.

Any idea how to shout about "hey this may take too long, why are you
doing it with irqs disabled?!"?

>
> --
> Michal Hocko
> SUSE Labs