linux-kernel - Re: [PATCH v2 3/3] genirq: Do not test disabled IRQs with DEBUG

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Date:   Wed, 17 Jun 2020 11:30:44 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mark Brown <broonie@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Vladimir Oltean <vladimir.oltean@....com>,
        linux-spi@...r.kernel.org,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Wolfram Sang <wsa@...nel.org>, kernel@...gutronix.de
Subject: Re: [PATCH v2 3/3] genirq: Do not test disabled IRQs with DEBUG_SHIRQ

Mark Brown <broonie@...nel.org> writes:
> On Tue, Jun 16, 2020 at 12:11:17PM +0200, Krzysztof Kozlowski wrote:
>> On Mon, Jun 15, 2020 at 01:08:44PM +0100, Mark Brown wrote:
>> > On Mon, Jun 15, 2020 at 10:07:19AM +0200, Krzysztof Kozlowski wrote:
>> > > Testing events during freeing of disabled shared interrupts
>> > > (CONFIG_DEBUG_SHIRQ) leads to false positives.  The driver disabled
>> > > interrupts on purpose to be sure that they will not fire during device
>> > > removal.
>
>> > Surely the whole issue with shared IRQs that's being tested for here is
>> > that when the interrupt is shared some other device connected to the
>> > same interrupt line may trigger an interrupt regardless of what's going
>> > on with this device?
>
>> Yes. However if that device disabled the interrupt, it should not be
>> fired for other users. In such case the testing does not point to a
>> real issue.
>
> To be honest I'd say that if you're disabling a shared interrupt that's
> a bit of an issue regardless of anything else that's going on, it'll
> disrupt other devices connected to it.

Correct.

Shared interrupts are broken by design and I really can't understand why
hardware people still insist on them.

Thanks,

        tglx