From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759065Ab0J0ICE (ORCPT ); Wed, 27 Oct 2010 04:02:04 -0400 Received: from www.tglx.de ([62.245.132.106]:33220 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755195Ab0J0ICB (ORCPT ); Wed, 27 Oct 2010 04:02:01 -0400 Date: Wed, 27 Oct 2010 10:01:45 +0200 (CEST) From: Thomas Gleixner To: Abhijeet Dharmapurikar cc: Ingo Molnar , "H. Peter Anvin" , linux-kernel@vger.kernel.org, linux-arm-msm-owner@vger.kernel.org Subject: Re: [RFC IRQ] genirq: fix handle_nested_irq for lazy disable In-Reply-To: <1288144209-28086-1-git-send-email-adharmap@codeaurora.org> Message-ID: References: <1288144209-28086-1-git-send-email-adharmap@codeaurora.org> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 26 Oct 2010, adharmap@codeaurora.org wrote: > From: Abhijeet Dharmapurikar > > When lazy disabling is implemented and an interrupt is disabled the > genirq code ends up marking it as IRQ_DISABLED in the descriptor. > The interrupt stays enabled in the controller. If the interrupt > fires after disabling, the flow handlers namely handle_level_irq and > handle_edge_irq mask the interrupt in the controller. > > This is not the case with handle_nested_irq. The interrupt stays enabled in > the controller and if it were a level interrupt it keeps firing only to be > ignored by handle_nested_irq. > > Update handle_nested_irq to mask such an interrupt. > > Change-Id: Id0fa3280c49a36aa8b8db1d5cc20472bf5e53c5f > Signed-off-by: Abhijeet Dharmapurikar > --- > This problem shows up on my hardware because the interrupt controller is > over a slow bus and it doesnt deactivate the interrupt line to the processor > until an ack or mask operation is carried out for each of its active > interrupts. > > I could have updated the interrupt controller thread itself to check if the > interrupt is marked IRQ_DISABLED but didn't seem right to take the > desc->lock in there. Instead updating handle_nested_irq to handle this > seemed like the right thing to do. > > kernel/irq/chip.c | 10 +++++++++- > 1 files changed, 9 insertions(+), 1 deletions(-) > > diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c > index baa5c4a..35ccc41 100644 > --- a/kernel/irq/chip.c > +++ b/kernel/irq/chip.c > @@ -419,6 +419,7 @@ void handle_nested_irq(unsigned int irq) > { > struct irq_desc *desc = irq_to_desc(irq); > struct irqaction *action; > + int mask_this_irq = 0; > irqreturn_t action_ret; > > might_sleep(); > @@ -428,8 +429,10 @@ void handle_nested_irq(unsigned int irq) > kstat_incr_irqs_this_cpu(irq, desc); > > action = desc->action; > - if (unlikely(!action || (desc->status & IRQ_DISABLED))) > + if (unlikely(!action || (desc->status & IRQ_DISABLED))) { > + mask_this_irq = 1; > goto out_unlock; > + } > > desc->status |= IRQ_INPROGRESS; > raw_spin_unlock_irq(&desc->lock);e > @@ -443,6 +446,11 @@ void handle_nested_irq(unsigned int irq) > > out_unlock: > raw_spin_unlock_irq(&desc->lock); > + if (unlikely(mask_this_irq)) { > + chip_bus_lock(irq, desc); > + desc->chip->mask(irq); That does not work with current mainline due to the irq_chip changes, can you please respin against linus latest? Also there is no requirement for irq_chip instances to implement the mask function, so this might crash the kernel for innocent users of that infrastructure. mask_irq() is your friend. Aside of that this wont work for edge triggered interrupts, as you'd loose the edge, so this needs more thought and a thorough look at the users of handle_nested_irq(). One possible solution would be to change handle_nested_irq() to return int. So we could return 0 for the normal case and some sensible error code when the irq is disabled, so the caller can deal with it. Either that or we need a separate nested function for level irqs which then can implement the mask logic. Thanks, tglx