Messages in this thread | | | Subject | RE: [PATCH] genirq: for edge interrupt IRQS_ONESHOT support with irq thread | From | anish kumar <> | Date | Sun, 21 Oct 2012 23:45:08 +0900 |
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On Sat, 2012-10-13 at 14:21 +0900, anish kumar wrote: > On Fri, 2012-10-12 at 22:52 +0200, Thomas Gleixner wrote: > > On Fri, 12 Oct 2012, Liu, Chuansheng wrote: > > > > -----Original Message----- > > > > From: anish kumar [mailto:anish198519851985@gmail.com] > > > > Sent: Friday, October 12, 2012 11:25 PM > > > > To: Liu, Chuansheng > > > > Cc: Thomas Gleixner; linux-kernel@vger.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 > > > I means because it is masked, if at this time device issues edge irq, > > > It will not be delivered and lost. > > > > No, it is NOT lost. The irq is marked PENDING already, so we invoke > It is fairly easy for an edge triggered interrupt to be missed - for > example if interrupts have to be masked for a period - and unless there > is some type of hardware latch that records the event it is impossible > to recover. > tglx, explanation will only work if we have a hardware latch which when > unmasked sends all those edge interrupts again (which had come when it > was masked while the CPU was handling the same interrupts). > > PS:http://kernel.org/doc/htmldocs/genericirq.html Hello tglx, Does this explanation makes sense? > > the handler again and handle it. And before we invoke the handler > > another time we unmask it. > > > > It does not matter at all whether the interrupt has been sent five > > times while it was masked. What matters is that we recorded the first > > one and set the PENDING flag. That way we invoke the interrupt handler > > again and keep stuff rolling. > > > > Thanks, > > > > tglx >
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