Date: Wed, 15 Dec 2010 10:48:25 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Jan Kiszka <jan.kiszka@siemens.com>
cc: Jan Kiszka <jan.kiszka@web.de>, Avi Kivity <avi@redhat.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>, Tom Lyon <pugs@cisco.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH v3 2/4] genirq: Inform handler about line sharing state
In-Reply-To: <4D088C77.8030701@siemens.com>
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References: <cover.1292281184.git.jan.kiszka@web.de> <a59c76552ebeaa128022ba9bcc7ea0753b312447.1292281184.git.jan.kiszka@web.de> <alpine.LFD.2.00.1012142243540.12146@localhost6.localdomain6> <4D07F738.8080204@web.de> <alpine.LFD.2.00.1012150903560.12146@localhost6.localdomain6>
 <4D088C77.8030701@siemens.com>
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On Wed, 15 Dec 2010, Jan Kiszka wrote:
> 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@siemens.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.

Darn. Will think more about it.
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