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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Mark Brown <broonie@kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>
Cc:     Vladimir Oltean <vladimir.oltean@nxp.com>,
        linux-spi@vger.kernel.org,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        Wolfram Sang <wsa@kernel.org>, kernel@pengutronix.de
Subject: Re: [PATCH v2 3/3] genirq: Do not test disabled IRQs with DEBUG_SHIRQ
In-Reply-To: <20200616103956.GL4447@sirena.org.uk>
References: <1592208439-17594-1-git-send-email-krzk@kernel.org> <1592208439-17594-3-git-send-email-krzk@kernel.org> <20200615120844.GL4447@sirena.org.uk> <CAJKOXPfEpLN9jS11WW367Na3Ukfi8p3urKDcJoafg9dHuCDSUA@mail.gmail.com> <20200616103956.GL4447@sirena.org.uk>
Date:   Wed, 17 Jun 2020 11:30:44 +0200
Message-ID: <87mu52ca4b.fsf@nanos.tec.linutronix.de>
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Mark Brown <broonie@kernel.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