Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752095Ab2JMFVL (ORCPT ); Sat, 13 Oct 2012 01:21:11 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:37296 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751469Ab2JMFVK (ORCPT ); Sat, 13 Oct 2012 01:21:10 -0400 Subject: RE: [PATCH] genirq: for edge interrupt IRQS_ONESHOT support with irq thread From: anish kumar To: Thomas Gleixner , "Liu, Chuansheng" Cc: "linux-kernel@vger.kernel.org" In-Reply-To: References: <1350045084.13178.19.camel@cliu38-desktop-build> <27240C0AC20F114CBF8149A2696CBE4A19587A@SHSMSX101.ccr.corp.intel.com> <27240C0AC20F114CBF8149A2696CBE4A1958B9@SHSMSX101.ccr.corp.intel.com> <27240C0AC20F114CBF8149A2696CBE4A195A6B@SHSMSX101.ccr.corp.intel.com> <1350055478.8329.24.camel@anish-Inspiron-N5050> <27240C0AC20F114CBF8149A2696CBE4A195A8D@SHSMSX101.ccr.corp.intel.com> Content-Type: text/plain; charset="UTF-8" Date: Sat, 13 Oct 2012 14:21:03 +0900 Message-ID: <1350105663.8329.50.camel@anish-Inspiron-N5050> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2456 Lines: 51 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 > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/