From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: Hang: 2.6.32.4 sky2/DMAR (was [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check_sync) Date: Thu, 28 Jan 2010 09:08:35 -0800 Message-ID: <20100128090835.0d93e53a@nehalam> References: <20100120094103.GA6225@ff.dom.local> <4B58B217.8030001@majjas.com> <20100121204133.GB3085@del.dom.local> <4B59E7EB.3050605@majjas.com> <20100122215304.GA3105@del.dom.local> <4B5A2362.6000306@majjas.com> <20100122230605.GB3105@del.dom.local> <4B5A33D8.90501@majjas.com> <20100122234656.GC3105@del.dom.local> <4B5A39BD.8020305@majjas.com> <20100123232133.GA3487@del.dom.local> <4B605D1B.60402@majjas.com> <20100127085049.5b5048e9@nehalam> <4B60707F.1000608@majjas.com> <20100127095614.14313677@nehalam> <4B608128.7090607@majjas.com> <4B6089C7.4010803@majjas.com> <4B61ADF1.7060705@majjas.com> <4B61BEA4.1030905@majjas.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Jarek Poplawski , David Miller , akpm@linux-foundation.org, flyboy@gmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Michael Chan , Don Fry , Francois Romieu , Matt Carlson To: Michael Breuer Return-path: In-Reply-To: <4B61BEA4.1030905@majjas.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, 28 Jan 2010 11:43:16 -0500 Michael Breuer wrote: > Update: I played with dma-debug. Was being disabled due to lack of > memory. I forced it back on while pumping traffic through and got this: > Jan 28 11:39:30 mail kernel: ------------[ cut here ]------------ > Jan 28 11:39:30 mail kernel: WARNING: at lib/dma-debug.c:902 > check_sync+0xc1/0x43f() > Jan 28 11:39:30 mail kernel: Hardware name: System Product Name > Jan 28 11:39:30 mail kernel: sky2 0000:06:00.0: DMA-API: device driver > tries to sync DMA memory it has not allocated [device This test in dma-debug is bogus. Because the debug code matches dma based on address and size; and is perfectly valid to sync a value less than size. This is the patch I sent earlier, it isn't 100% correct but it will let you keep testing .................................... This should fix the dma-debug API code (and documentation), to avoid false positives when sync is done on a partial map. Signed-off-by: Stephen Hemminger --- a/Documentation/DMA-API.txt 2010-01-20 15:17:01.390143729 -0800 +++ b/Documentation/DMA-API.txt 2010-01-20 15:18:48.967875255 -0800 @@ -377,9 +377,10 @@ void pci_dma_sync_sg(struct pci_dev *hwdev, struct scatterlist *sg, int nelems, int direction) -Synchronise a single contiguous or scatter/gather mapping. All the -parameters must be the same as those passed into the single mapping -API. +Synchronise a single contiguous or scatter/gather mapping. The +device and handle must be the same as those passed into the single mapping +API. The size can be less than the original mapping if only part +of the mapping needs to be accessed. Notes: You must do this: --- a/lib/dma-debug.c 2010-01-20 15:22:55.919519883 -0800 +++ b/lib/dma-debug.c 2010-01-20 15:26:31.648895638 -0800 @@ -285,11 +285,9 @@ static struct dma_debug_entry *hash_buck } /* - * If we have multiple matches but no perfect-fit, just return - * NULL. + * If we have multiple matches but no perfect-fit + * return best value and let caller deal with it. */ - ret = (matches == 1) ? ret : NULL; - return ret; }