From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933964AbdKBRd4 convert rfc822-to-8bit (ORCPT ); Thu, 2 Nov 2017 13:33:56 -0400 Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:60086 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933113AbdKBRdx (ORCPT ); Thu, 2 Nov 2017 13:33:53 -0400 Date: Thu, 2 Nov 2017 18:33:50 +0100 From: Sebastian Andrzej Siewior To: Joerg Roedel Cc: iommu@lists.linux-foundation.org, vinadhy@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] iommu/iova: Use raw_cpu_ptr() instead of get_cpu_ptr() for ->fq Message-ID: <20171102173349.btd3b2xfklcfopmz@breakpoint.cc> References: <20170906103459.oi2nn7jondjqdo5m@linutronix.de> <20170919094119.bibxslqyeefbx7gf@8bytes.org> <20170921152140.grayy3a7ok2im7xa@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <20170921152140.grayy3a7ok2im7xa@linutronix.de> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-09-21 17:21:40 [+0200], Sebastian Andrzej Siewior wrote: > get_cpu_ptr() disabled preemption and returns the ->fq object of the > current CPU. raw_cpu_ptr() does the same except that it not disable > preemption which means the scheduler can move it to another CPU after it > obtained the per-CPU object. > In this case this is not bad because the data structure itself is > protected with a spin_lock. This change shouldn't matter however on RT > it does because the sleeping lock can't be accessed with disabled > preemption. Did this make to your tree Jörg? > Cc: Joerg Roedel > Cc: iommu@lists.linux-foundation.org > Reported-by: vinadhy@gmail.com > Signed-off-by: Sebastian Andrzej Siewior > --- > On 2017-09-19 11:41:19 [+0200], Joerg Roedel wrote: > > Hi Sebastian, > Hi Jörg, > > > I moved the flushing to driver/iommu/iova.c to share it with the Intel > > IOMMU and possibly other drivers too, so this patch does no longer apply > > to v4.14-rc1. Can you update the patch to these changes? > > Sure. > > v1…v2: move the change from amd_iommu.c to iova.c > > drivers/iommu/iova.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c > index 33edfa794ae9..b30900025c62 100644 > --- a/drivers/iommu/iova.c > +++ b/drivers/iommu/iova.c > @@ -570,7 +570,7 @@ void queue_iova(struct iova_domain *iovad, > unsigned long pfn, unsigned long pages, > unsigned long data) > { > - struct iova_fq *fq = get_cpu_ptr(iovad->fq); > + struct iova_fq *fq = raw_cpu_ptr(iovad->fq); > unsigned long flags; > unsigned idx; > > @@ -600,8 +600,6 @@ void queue_iova(struct iova_domain *iovad, > if (atomic_cmpxchg(&iovad->fq_timer_on, 0, 1) == 0) > mod_timer(&iovad->fq_timer, > jiffies + msecs_to_jiffies(IOVA_FQ_TIMEOUT)); > - > - put_cpu_ptr(iovad->fq); > } > EXPORT_SYMBOL_GPL(queue_iova); > > -- > 2.14.1 > Sebastian