From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sander Eikelenboom Subject: Re: 3.14-mw regression: rtl8169 WARNING: DMA-API: exceeded 7 overlapping mappings of pfn 55ebe Date: Thu, 13 Feb 2014 22:49:22 +0100 Message-ID: <343228200.20140213224922@eikelenboom.it> References: <1859471893.20140126115521@eikelenboom.it> <20140127000305.GA14236@electric-eye.fr.zoreil.com> <84816226.20140206123631@eikelenboom.it> <942972114.20140206140909@eikelenboom.it> <1434499348.20140211205617@eikelenboom.it> <1392178661.1752.1.camel@edumazet-glaptop2.roam.corp.google.com> <1392322487.11022.4.camel@dwillia2-mobl2.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , Konrad Rzeszutek Wilk , Wei Liu , Francois Romieu , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Dave Jones , Russell King To: Dan Williams Return-path: In-Reply-To: <1392322487.11022.4.camel@dwillia2-mobl2.amr.corp.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Thursday, February 13, 2014, 9:14:47 PM, you wrote: > On Tue, 2014-02-11 at 20:17 -0800, Eric Dumazet wrote: >> On Tue, 2014-02-11 at 18:07 -0800, Dan Williams wrote: >> >> > The overlap granularity is too large. Multiple dma_map_single >> > mappings are allowed to a given page as long as they don't collide on >> > the same cache line. >> > >> >> I am not sure why you try number of mappings of a page. >> >> Try launching 100 concurrent netperf -t TCP_SENFILE >> >> Same page might be mapped more than 100 times, more than 10000 times in >> some cases. > Thanks for that test case. > I updated the fix patch with the following. > diff --git a/lib/dma-debug.c b/lib/dma-debug.c > index 42b12740940b..611010df1e9c 100644 > --- a/lib/dma-debug.c > +++ b/lib/dma-debug.c > @@ -513,6 +513,13 @@ static int active_cln_insert(struct dma_debug_entry *entry) > unsigned long flags; > int rc; > > + /* If the device is not writing memory then we don't have any > + * concerns about the cpu consuming stale data. This mitigates > + * legitimate usages of overlapping mappings. > + */ + if (entry->>direction == DMA_TO_DEVICE) > + return 0; > + > spin_lock_irqsave(&radix_lock, flags); > rc = radix_tree_insert(&dma_active_cacheline, to_cln(entry), entry); > if (rc == -EEXIST) > @@ -526,6 +533,10 @@ static void active_cln_remove(struct dma_debug_entry *entry) > { > unsigned long flags; > > + /* ...mirror the insert case */ + if (entry->>direction == DMA_TO_DEVICE) > + return; > + > spin_lock_irqsave(&radix_lock, flags); > /* since we are counting overlaps the final put of the > * cacheline will occur when the overlap count is 0. > Sander, barring a negative test result from you I'll send the attached > patch to Andrew. Hi Dan, That seems to effectively suppress the warning, thanks and: Tested-by; Sander Eikelenboom -- Sander > -- > Dan