linux-kernel - Re: [PATCH] genirq: Fix bad IRQ

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Message-ID: <20150918.195645.642918355603329874.okuno.kohji@jp.panasonic.com>
Date:	Fri, 18 Sep 2015 19:56:45 +0900
From:	Kohji Okuno <okuno.kohji@...panasonic.com>
To:	<marc.zyngier@....com>
CC:	<tglx@...utronix.de>, <linux-kernel@...r.kernel.org>,
	<okuno.kohji@...panasonic.com>
Subject: Re: [PATCH] genirq: Fix bad IRQ_ONSHOT in forced IRQ setting

From: Marc Zyngier <marc.zyngier@....com>
Date: Fri, 18 Sep 2015 11:03:12 +0100
> On Fri, 18 Sep 2015 18:22:07 +0900
> Kohji Okuno <okuno.kohji@...panasonic.com> wrote:
> 
>> From: Thomas Gleixner <tglx@...utronix.de>
>> Date: Fri, 18 Sep 2015 11:04:23 +0200
>> > That's weird. The flow is:
>> > 
>> > interrupt()
>> >   mask()
>> >   ret = primary_handler()
>> >   if (ret == WAKE_THREAD)
>> >     wake_thread()
>> >   else
>> >     unmask()
>> > 
>> > thread_handler()
>> >   ....
>> >   unmask()
>> > 
>> > So if an interrupt is triggered on the device while the interrupt is
>> > masked it should be raised again immediately when the unmask happens
>> > because its level type.
>> > 
>> > I'm wondering why that doesn't work.
>> 
>> Yes. I think so. And, I have just found that sdhci_thread_irq() don't
>> finish in this case. I'm analyzing about this now. But, after I apply
>> my patch, sdhci_thread_irq() can finish. I will share the result with
>> you.
> 
> What do you mean exactly by "don't finish"? Does it hang somewhere? Or
> keeps processing data but never drains?
> 
> Thanks,
> 
> 	M.

Hi Marc and tglx,

irq thread(runs sdhci_thread_irq()) is waiting on
drivers/mmc/core/core.c:mmc_wait_for_req_done() in order to access
a SDIO register. And, this thread shoud be woken up from
sdhci_irq() after the completion of the register access.
But, since the IRQ is masked, sdhci_irq() is not called and  irq
thread can not wake up. This is root cause, I think.
What do you think about this?

Best regards,
 Kohji Okuno

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