On Thu, Aug 24, 2023 at 11:04 PM Hou Tao <houtao@xxxxxxxxxxxxxxx> wrote:
>
> > Could you try the following:
> > diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
> > index 9c49ae53deaf..ee8262f58c5a 100644
> > --- a/kernel/bpf/memalloc.c
> > +++ b/kernel/bpf/memalloc.c
> > @@ -442,7 +442,10 @@ static void bpf_mem_refill(struct irq_work *work)
> >
> > static void notrace irq_work_raise(struct bpf_mem_cache *c)
> > {
> > - irq_work_queue(&c->refill_work);
> > + if (!irq_work_queue(&c->refill_work)) {
> > + preempt_disable_notrace();
> > + preempt_enable_notrace();
> > + }
> > }
> >
> > The idea that it will ask for resched if preemptible.
> > will it address the issue you're seeing?
> >
> > .
>
> No. It didn't work.
why?
> If you are concerning about the overhead of
> preempt_enabled_notrace(), we could use local_irq_save() and
> local_irq_restore() instead.
That's much better.
Moving local_irq_restore() after irq_work_raise() in process ctx
would mean that irq_work will execute immediately after local_irq_restore()
which would make bpf_ma to behave like sync allocation.
Which is the ideal situation. preempt disable/enable game is more fragile.
