netdev - Re: lan78xx: WARNING: irq 79 handler enabled interrupts

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Date:   Sat, 29 Dec 2018 09:41:38 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Stefan Wahren <stefan.wahren@...e.com>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        Eric Anholt <eric@...olt.net>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        <netdev@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: lan78xx: WARNING: irq 79 handler enabled interrupts

On Sat, 29 Dec 2018 00:02:57 +0000,
Stefan Wahren <stefan.wahren@...e.com> wrote:

Hi Stephan,

> 
> Hi,
> while booting my Raspberry Pi 3 B+ with Linux 4.20 (arm64/defconfig)
> i'm getting the following warning:
> 
> [   11.005738] irq 79 handler irq_default_primary_handler+0x0/0x8 enabled interrupts

[...]

> This seems to come from the lan78xx driver, because i don't get this
> warning on the RPI 3B (smsc95xx).
> 
> What's the approach to fix this issue?  Is it just simply replace
> spin_lock_irq() with spin_lock_irqsave() at the right places?

No, this is more pathological than that. The USB framework seems to be
using threaded interrupts, which implies that interrupts are
re-enabled as soon as it has run.

In turn, this driver is using handle_simple_irq() as its flow, which
definitely expect interrupts to be disabled.

I have no insight in how this driver works, but I'm happy to help if
someone explains the interrupt flow of this thing.

	M.

-- 
Jazz is not dead, it just smell funny.