linux-kernel - Re: [PATCH v3 2/4] genirq: Inform handler about line sharing state

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Message-ID: <4D088C77.8030701@siemens.com>
Date:	Wed, 15 Dec 2010 10:37:59 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Jan Kiszka <jan.kiszka@....de>, Avi Kivity <avi@...hat.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>, Tom Lyon <pugs@...co.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH v3 2/4] genirq: Inform handler about line sharing state

Am 15.12.2010 09:05, Thomas Gleixner wrote:
> On Wed, 15 Dec 2010, Jan Kiszka wrote:
> 
>> Am 14.12.2010 22:46, Thomas Gleixner wrote:
>>> On Mon, 13 Dec 2010, Jan Kiszka wrote:
>>>> From: Jan Kiszka <jan.kiszka@...mens.com>
>>>>  	chip_bus_lock(desc);
>>>>  	retval = __setup_irq(irq, desc, action);
>>>>  	chip_bus_sync_unlock(desc);
>>>>  
>>>> -	if (retval)
>>>> +	if (retval) {
>>>> +		if (desc->action && !desc->action->next)
>>>> +			desc->irq_data.drv_status &= ~IRQS_SHARED;
>>>
>>> This is redundant. IRQS_SHARED gets set in a code path where all
>>> checks are done already.
>>
>> Nope, it's also set before entry of __setup_irq in case we call an
>> IRQF_ADAPTIVE handler.
>>
>> We need to set it that early as we may race with IRQ events for the
>> already registered handler happening between the sharing notification
>> and the actual registration of the second handler.
> 
> Hmm, ok. Though the MAKE_SHAREABLE flag should be sufficient to do the
> notification.

For notification, yes. But we need SHARED once we reenable the line
after the notification.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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