linux-kernel - Re: [PATCH] genirq: Check irq disabled & masked states in irq

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Date:   Sat, 27 May 2017 10:16:37 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     jeffy <jeffy.chen@...k-chips.com>
cc:     LKML <linux-kernel@...r.kernel.org>, briannorris@...omium.org,
        dianders@...omium.org, tfiga@...omium.org,
        Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH] genirq: Check irq disabled & masked states in
 irq_shutdown

On Sat, 27 May 2017, jeffy wrote:
> On 05/26/2017 09:20 PM, Thomas Gleixner wrote:
> > On Fri, 26 May 2017, Jeffy Chen wrote:
> > 
> > > If irq is already disabled and masked, we would hit a unbalanced irq
> > > shutdown/disable/mask when freeing it.
> > 
> > Errr? What exactly is unbalanced? None of the called functions has any
> > counter or whatever.
> > 
> > Can you please explain what you are trying to fix?
> 
> sorry, i'll try to rewrite the commit message.
> 
> for example when a driver(drivers/net/wireless/marvell/mwifiex/main.c) try to
> do these:
> 
> devm_request_irq->irq_startup->irq_enable
> disable_irq                                     <-- disabled and masked
> devm_free_irq->irq_shutdown                     <-- disable it again

This driver is broken as hell. It requests the interrupt _BEFORE_ the whole
thing is initialized. If there is a pending interrupt on that line, it will
explode nicely before it is able to disable the irq. But that's a different
problem.

Thanks,

	tglx