RE: [PATCH] genirq: for edge interrupt IRQS_ONESHOT support withirq thread

[anish kumar]

On Fri, 2012-10-12 at 15:29 +0000, Liu, Chuansheng wrote:
> 
> > -----Original Message-----
> > From: anish kumar [mailto:anish198519851985@xxxxxxxxx]
> > Sent: Friday, October 12, 2012 11:25 PM
> > To: Liu, Chuansheng
> > Cc: Thomas Gleixner; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: RE: [PATCH] genirq: for edge interrupt IRQS_ONESHOT support with irq
> > thread
> > 
> > On Fri, 2012-10-12 at 14:57 +0000, Liu, Chuansheng wrote:
> > > > On SMP an interrupt which is raised after the ack() again before the
> > > > handler finishes, can invoke another delivery on a different CPU,
> > > > which then sees the IRQ_INPROGESS flag, masks it and flags it
> > > > PENDING. When the primary handler on the first CPU returns, it sees
> > > > the PENDING flag, unmasks and invokes the handler another time.
> > > In this case, when IRQ_INPROGRESS flag is set, on another CPU, it will
> > > mask and ack it, if before the primary handler on the first CPU returns,
> > > the edge interrupt is raised again, it will be lost, right?
> > Why will the interrupt be raised again?Is not it masked?I read tglx
> I means because it is masked, if at this time device issues edge irq,
> It will not be delivered and lost.
That depends on the hardware, doesn't it?If if the frequency of
interrupt is too much that device is not able to cope up with that then
don't you think that the interrupt controller is faulty?

Well I am not a expert on the hardware but it looks to me that the
hardware should be at a fault here.
> 
> > statement as this:if the interrupt is being handled on one core, then
> > the delivery of new interrupt can be on the second core and in that case
> > it will see IRQ_INPROGRESS flag and it will *mask* it and set the flag
> > as pending.So there is no chance of any new interrupt.
> > > So I think set PENDING just confirm one time, it just depends on primary
> > handler
> > > execution time and irq frequency.
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> 


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