linux-kernel - Re: [PATCH v4 3/5] irqchip: sifive-plic: Add warning in plic

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Message-ID: <CAAhSdy19yrGsXADNNSF8kuoUULqZCFdZ4JKc3_hxBZKHf=dJrg@mail.gmail.com>
Date:   Sat, 19 Jan 2019 10:33:55 +0530
From:   Anup Patel <anup@...infault.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Atish Patra <atish.patra@....com>,
        linux-riscv@...ts.infradead.org,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] irqchip: sifive-plic: Add warning in plic_init()
 if handler already present

On Tue, Jan 15, 2019 at 9:24 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Thu, Dec 27, 2018 at 04:48:19PM +0530, Anup Patel wrote:
> > We have two enteries (one for M-mode and another for S-mode) in the
> > interrupts-extended DT property of PLIC DT node for each HART. It is
> > expected that firmware/bootloader will set M-mode HWIRQ line of each
> > HART to 0xffffffff (i.e. -1) in interrupts-extended DT property
> > because Linux runs in S-mode only.
> >
> > If firmware/bootloader is buggy then it will not correctly update
> > interrupts-extended DT property which might result in a plic_handler
> > configured twice. This patch adds a warning in plic_init() if a
> > plic_handler is already marked present. This warning provides us
> > a hint about incorrectly updated interrupts-extended DT property.
> >
> > Signed-off-by: Anup Patel <anup@...infault.org>
> > Reviewed-by: Christoph Hellwig <hch@....de>
> > ---
> >  drivers/irqchip/irq-sifive-plic.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> > index 01bbbbffbcae..b9a0bcefe426 100644
> > --- a/drivers/irqchip/irq-sifive-plic.c
> > +++ b/drivers/irqchip/irq-sifive-plic.c
> > @@ -229,6 +229,11 @@ static int __init plic_init(struct device_node *node,
> >
> >               cpu = riscv_hartid_to_cpuid(hartid);
> >               handler = per_cpu_ptr(&plic_handlers, cpu);
> > +             if (handler->present) {
> > +                     pr_warn("handler already present for context %d.\n", i);
> > +                     continue;
> > +             }
> > +
>
> Just use WARN_ON_ONCE?

WARN_ON_ONCE() is not suitable here because we want know
all the context IDs for which handler is already present.

Regards,
Anup