RE: [RESEND 1/1] gic: its: Make sure a LPI is discarded before free.

From: Zhao, Yuanyuan
Date: Wed Jan 09 2019 - 04:29:56 EST


Hi Marc:

Thank you for your reply.

As you said, APIs such as free_irq will deactivate irq
before free it. But deactivation is not forced by every API,
for example irq_dispose_mapping. So I think it's better to check
that irq was deactivated as expected.

BRs,
Yuanyuan


> -----Original Message-----
> From: Marc Zyngier [mailto:marc.zyngier@xxxxxxx]
> Sent: 2019年1月9日 15:43
> To: Zhao, Yuanyuan <yuanyuan.zhao@xxxxxxxxxxxxxxxx>
> Cc: tglx@xxxxxxxxxxxxx; jason@xxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; Zheng, Joey
> <yu.zheng@xxxxxxxxxxxxxxxx>; Wang, Dongsheng <dongsheng.wang@hxt-
> semitech.com>
> Subject: Re: [RESEND 1/1] gic: its: Make sure a LPI is discarded before free.
>
> On Wed, 9 Jan 2019 11:53:27 +0800
> Zhao Yuanyuan <yuanyuan.zhao@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Zhao,
>
> > Its device will be removed after all events be freed.
> > Undisarded events can lead to unpredictable behaviar.
> >
> > Signed-off-by: Zhao Yuanyuan <yuanyuan.zhao@xxxxxxxxxxxxxxxx>
> > ---
> > drivers/irqchip/irq-gic-v3-its.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c
> > b/drivers/irqchip/irq-gic-v3-its.c
> > index db20e99..4fee008 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -2572,6 +2572,10 @@ static void its_irq_domain_free(struct
> irq_domain *domain, unsigned int virq,
> > virq + i);
> > u32 event = its_get_event_id(data);
> >
> > + /* Discard irq before free */
> > + if (irqd_is_activated(d))
> > + its_send_discard(its_dev, event);
> > +
> > /* Mark interrupt index as unused */
> > clear_bit(event, its_dev->event_map.lpi_map);
> >
>
> But we already do send a discard on deactivate, which logically happens
> before we free the domain. So what are you fixing here?
>
> Thanks,
>
> M.
> --
> Without deviation from the norm, progress is not possible.