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

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Date:   Wed, 9 Jan 2019 09:29:41 +0000
From:   "Zhao, Yuanyuan" <yuanyuan.zhao@...-semitech.com>
To:     Marc Zyngier <marc.zyngier@....com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "jason@...edaemon.net" <jason@...edaemon.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "Zheng, Joey" <yu.zheng@...-semitech.com>,
        "Wang, Dongsheng" <dongsheng.wang@...-semitech.com>
Subject: RE: [RESEND 1/1] gic: its: Make sure a LPI is discarded before free.

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@....com]
> Sent: 2019年1月9日 15:43
> To: Zhao, Yuanyuan <yuanyuan.zhao@...-semitech.com>
> Cc: tglx@...utronix.de; jason@...edaemon.net; linux-
> kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; Zheng, Joey
> <yu.zheng@...-semitech.com>; Wang, Dongsheng <dongsheng.wang@...-
> 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@...-semitech.com> 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@...-semitech.com>
> > ---
> >  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.