netdev - Re: Hang: 2.6.32.4 sky2/DMAR (was [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check

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Date:	Thu, 28 Jan 2010 17:43:34 -0500
From:	Michael Breuer <mbreuer@...jas.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Stephen Hemminger <shemminger@...ux-foundation.org>,
	David Miller <davem@...emloft.net>, akpm@...ux-foundation.org,
	flyboy@...il.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Michael Chan <mchan@...adcom.com>,
	Don Fry <pcnet32@...izon.net>,
	Francois Romieu <romieu@...zoreil.com>,
	Matt Carlson <mcarlson@...adcom.com>
Subject: Re: Hang: 2.6.32.4 sky2/DMAR (was [PATCH] sky2: Fix WARNING: at
 lib/dma-debug.c:902 check_sync)

On 1/28/2010 5:34 PM, Jarek Poplawski wrote:
> On Thu, Jan 28, 2010 at 01:46:17PM -0500, Michael Breuer wrote:
>    
>> On 1/28/2010 12:08 PM, Stephen Hemminger wrote:
>>      
>>> --- 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;
>>>   }
>>>
>>>        
>> Ok - applied. Noise gone... however I'm not sure whether I'll be
>> able to keep dma-debug going long enough to catch anything.
>> num_free_entries keeps dropping... looks like entries are not freed.
>> I'm running with a huge number for now&  sky2 as the driver filter.
>> Is there a reason that entries wouldn't be unmapped, or is
>> dma-debug.c just not processing the unmap correctly?
>>      
> Do you mean it's after this patch or earlier too? I think you might
> use my sky2/receive_copy/pci_unmap_len patch instead to get rid of
> this warning.
>
> Btw, since 1000 was too much, maybe you could try copybreak=256 yet,
> plus additional ping or some other source of shorter packets. And how
> about trying this new switch?
>
> Jarek P.
>    
This is with the pci_unmap_len patch as well as the dma-debug patch. I'm 
not getting any warnings - but dma-debug num-free-entries drops until 
zero and then debugging is disabled. I started with 8,000,000 about 
three hours ago - without load I'm already down to less than half that. 
Again - only looking at sky2. Looks like the dma-debug hash table is 
reducing one entry for every packet, but never increasing the 
num_entries (no unmap perhaps).
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