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

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Message-ID: <alpine.LFD.2.00.1012150903560.12146@localhost6.localdomain6>
Date:	Wed, 15 Dec 2010 09:05:04 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jan Kiszka <jan.kiszka@....de>
cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	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>,
	Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH v3 2/4] genirq: Inform handler about line sharing state

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.

Thanks,

	tglx
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