From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755490Ab1BSTIJ (ORCPT ); Sat, 19 Feb 2011 14:08:09 -0500 Received: from rcsinet10.oracle.com ([148.87.113.121]:50721 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755014Ab1BSTIG (ORCPT ); Sat, 19 Feb 2011 14:08:06 -0500 Message-ID: <4D6014F9.8040605@kernel.org> Date: Sat, 19 Feb 2011 11:07:37 -0800 From: Yinghai Lu User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20101125 SUSE/3.0.11 Thunderbird/3.0.11 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, tglx@linutronix.de CC: linux-tip-commits@vger.kernel.org Subject: Re: [tip:irq/core] genirq: Make nr_irqs runtime expandable References: In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Source-IP: acsmt355.oracle.com [141.146.40.155] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090208.4D601505.00DA,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/19/2011 04:15 AM, tip-bot for Thomas Gleixner wrote: > Commit-ID: e7bcecb7b1d29b9ad5af939149a945658620ca8f > Gitweb: http://git.kernel.org/tip/e7bcecb7b1d29b9ad5af939149a945658620ca8f > Author: Thomas Gleixner > AuthorDate: Wed, 16 Feb 2011 17:12:57 +0100 > Committer: Thomas Gleixner > CommitDate: Sat, 19 Feb 2011 12:58:06 +0100 > > genirq: Make nr_irqs runtime expandable > > We face more and more the requirement to expand nr_irqs at > runtime. The reason are irq expanders which can not be detected in the > early boot stage. So we speculate nr_irqs to have enough room. Further > Xen needs extra irq numbers and we really want to avoid adding more > "detection" code into the early boot. There is no real good reason why > we need to limit nr_irqs at early boot. > > Allow the allocation code to expand nr_irqs. We have already 8k extra > number space in the allocation bitmap, so lets use it. > > Signed-off-by: Thomas Gleixner > --- > kernel/irq/irqdesc.c | 22 +++++++++++++++++++--- > 1 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c > index a250d3a..6f6644f 100644 > --- a/kernel/irq/irqdesc.c > +++ b/kernel/irq/irqdesc.c > @@ -206,6 +206,14 @@ struct irq_desc * __ref irq_to_desc_alloc_node(unsigned int irq, int node) > return NULL; > } > > +static int irq_expand_nr_irqs(unsigned int cnt) > +{ > + if (nr_irqs + cnt > IRQ_BITMAP_BITS) > + return -ENOMEM; > + nr_irqs += cnt; > + return 0; > +} > + > int __init early_irq_init(void) > { > int i, initcnt, node = first_online_node; > @@ -287,6 +295,12 @@ static inline int alloc_descs(unsigned int start, unsigned int cnt, int node) > { > return start; > } > + > +static int irq_expand_nr_irqs(unsigned int cnt) > +{ > + return -ENOMEM; > +} > + > #endif /* !CONFIG_SPARSE_IRQ */ > > /* Dynamic interrupt handling */ > @@ -335,9 +349,11 @@ irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node) > if (irq >=0 && start != irq) > goto err; > > - ret = -ENOMEM; > - if (start >= nr_irqs) > - goto err; > + if (start >= nr_irqs) { > + ret = irq_expand_nr_irqs(cnt); > + if (ret) > + goto err; > + } may need following patch. [PATCH] genirq: use IRQ_BITMAP_BITS as search size instead of nr_irqs. Otherwise bitmap_find_next_area could exit with larger start and in extreme case we could fail to get wrong irqs return. For example: IRQ_BITMAP_BITS=10240 nr_irqs=8192 cnt=2048 and bit 0 to bit 8190 are set already. before patch start from bit_find_next_area() will be 8191+2048. later irq_expand_nr_irqs will set nr_irqs 10240. finally irq_alloc_descs will return [8191+2048, 8191+2048+2047] happily.. with this patch, will get correct [8191, 8191+2047] Signed-off-by: Yinghai Lu --- kernel/irq/irqdesc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) Index: linux-2.6/kernel/irq/irqdesc.c =================================================================== --- linux-2.6.orig/kernel/irq/irqdesc.c +++ linux-2.6/kernel/irq/irqdesc.c @@ -346,12 +346,13 @@ irq_alloc_descs(int irq, unsigned int fr mutex_lock(&sparse_irq_lock); - start = bitmap_find_next_zero_area(allocated_irqs, nr_irqs, from, cnt, 0); + start = bitmap_find_next_zero_area(allocated_irqs, IRQ_BITMAP_BITS, + from, cnt, 0); ret = -EEXIST; if (irq >=0 && start != irq) goto err; - if (start >= nr_irqs) { + if (start + cnt > nr_irqs) { ret = irq_expand_nr_irqs(cnt); if (ret) goto err;