linux-kernel - RE: [PATCH] genirq: for edge interrupt IRQS

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Date:	Sat, 13 Oct 2012 00:24:38 +0900
From:	anish kumar <anish198519851985@...il.com>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
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
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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