Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757980Ab3FEWqq (ORCPT ); Wed, 5 Jun 2013 18:46:46 -0400 Received: from mail-ea0-f180.google.com ([209.85.215.180]:46026 "EHLO mail-ea0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757660Ab3FEWqp (ORCPT ); Wed, 5 Jun 2013 18:46:45 -0400 From: Grant Likely Subject: Re: [PATCH] No need to call irq_domain_legacy_revmap() for twice To: Mike Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, benh@kernel.crashing.org In-Reply-To: <1366181299.2439.1.camel@localhost> References: <1348479475-13074-1-git-send-email-qiudayu@linux.vnet.ibm.com> <20121126201739.13F213E09C2@localhost> <1353980506.2309.13.camel@localhost> <20121211083023.5C5D03E076D@localhost> <1366181299.2439.1.camel@localhost> Date: Wed, 05 Jun 2013 23:46:40 +0100 Message-Id: <20130605224640.7F60F3E10E4@localhost> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3651 Lines: 86 On Wed, 17 Apr 2013 14:48:19 +0800, Mike wrote: > 在 2012-12-11二的 08:30 +0000，Grant Likely写道： > > On Tue, 27 Nov 2012 09:41:46 +0800, Mike wrote: > > > 在 2012-11-26一的 20:17 +0000，Grant Likely写道： > > > > On Mon, 24 Sep 2012 17:37:55 +0800, Mike Qiu wrote: > > > > > Function irq_create_mapping() calls irq_find_mapping(). The later > > > > > function has checked if the indicated IRQ domain has hw IRQ mapped to > > > > > virtual IRQ through legacy mode or not and return the value of the > > > > > legacy irq number by call irq_domain_legacy_revmap(). We needn't > > > > > to call irq_domain_legacy_revmap() to do same check in > > > > > irq_create_mapping() again. > > > > > > > > > > The patch removes the duplicate call. > > > > > > > > > > Signed-off-by: Mike Qiu > > > > > --- > > > > > kernel/irq/irqdomain.c | 7 +++++-- > > > > > 1 files changed, 5 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c > > > > > index 49a7772..286d672 100644 > > > > > --- a/kernel/irq/irqdomain.c > > > > > +++ b/kernel/irq/irqdomain.c > > > > > @@ -547,9 +547,12 @@ unsigned int irq_create_mapping(struct irq_domain *domain, > > > > > return virq; > > > > > } > > > > > > > > > > - /* Get a virtual interrupt number */ > > > > > + /* > > > > > + * For IRQ domain with type of IRQ_DOMAIN_MAP_LEGACY, we needn't > > > > > + * create the IRQ mapping for non-existing one, so just return 0. > > > > > + */ > > > > > if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY) > > > > > - return irq_domain_legacy_revmap(domain, hwirq); > > > > > + return 0; > > > > > > > > But it does need to return the virq assigned to the hwirq. That is why > > > > it has to call the revmap function. > > > > > > > Yes, thanks > > > > > > this judgment has been done in > > > /*Check if mapping already exists*/ > > > virq = irq_find_mapping(domain, hwirq); > > > > > > if the virq equals none zero, the func irq_create_mapping will > > > return the virq value directly(already exists). > > > > > > otherwise, that means virq equals zero, this has two meanings, one is > > > haven't find the already exist mapping, the other one is in > > > irq_find_mapping() > > > case IRQ_DOMAIN_MAP_LEGACY: > > > return irq_domain_legacy_revmap(domain, hwirq); > > > this may return zero. > > > > > > So, when we check if it is a IRQ_DOMAIN_MAP_LEGACY, we just return zero > > > is OK. because if it is none zero, it will be return after check if > > > mapping already exists, and never come here. also we never try to assign > > > the virq for the legacy map. > > > > > > I don't know if you have understand my explanation. > > > > Yes, your explanation makes sense and you are correct. I'm not going to > > apply this for v3.8 (I've left it too late before the merge window), but > > I'll look again after the merge window closes. > > > Hi Grant > > I don't know if you forget this patch ... > > I haven't see this patch in 3.9-rc7 > > just for a reminder After taking another look at it, I'm not going to apply this patch. It isn't actively dangerous for the revmap to get called twice, and I've got a patch pending that removes the legacy map entirely and replaces it with a pre-populated linear map. g. -- 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/