linux-kernel - Re: [PATCH v2] dma-debug: enhance dma_debug_device

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Date:	Fri, 10 Jan 2014 17:25:45 -0700
From:	Shuah Khan <shuah.kh@...sung.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	akpm@...ux-foundation.org, alexander.h.duyck@...el.com,
	linux-kernel@...r.kernel.org, shuahkhan@...il.com,
	Shuah Khan <shuah.kh@...sung.com>,
	"shuahkhan@...il.com" <shuahkhan@...il.com>
Subject: Re: [PATCH v2] dma-debug: enhance dma_debug_device_change() to check
 for mapping errors

On 01/07/2014 10:22 AM, Shuah Khan wrote:
> On 01/07/2014 08:12 AM, Joerg Roedel wrote:
>> On Tue, Jan 07, 2014 at 08:00:33AM -0700, Shuah Khan wrote:
>>> This patch and a follow-on cocinelli warning fix patch are in
>>> linux-next. Would you like me to send a patch relative to the change
>>> in linux-next or cut a new patch against the latest Linus's git. I
>>> can go either way. We just have to remember to drop those two
>>> patches from linux-next.
>>
>> Please do a patch against linus.git and drop the two patches from
>> linux-next. Over which tree did they go into linux-next anyway?
>>
>>
>
> ok. It went through mm tree.
>

I have a separate routine now for scanning for entries with map error 
flag set and I also have a new err_printk() call to print the entry from 
dma_debug_device_change() right after device_dma_allocations() check and 
corresponding err_printk(). Snippet of the diff below. Only one warning 
gets printed. Looking at err_printk(): if (!show_all_errors && 
show_num_errors > 0) conditional, it appears that is the way it is 
supposed to work, unless I am missing something

One way to not miss the second warning is to just generate just a 
pr_err() for the mapping error instead of err_printk(). Leaked entries 
is a bigger problem that should really be shown and the same entry might 
not have the map error flag set. Thoughts?

  static int dma_debug_device_change(struct notifier_block *nb, unsigned 
long action, void *data)
  {
         struct device *dev = data;
@@ -758,6 +784,18 @@ static int dma_debug_device_change(struct 
notifier_block *nb, unsigned long acti
                                 "[mapped with %s] [mapped as %s]\n",
                         count, entry->dev_addr, entry->size,
                         dir2name[entry->direction], 
type2name[entry->type]);
+
+               count = device_dma_map_errors(dev, &entry);
+               if (count == 0)
+                       break;
+               err_printk(dev, entry,
+                               "DMA-API: device driver failed to check 
map err"
+                               ": [count=%d]\n"
+                               "Details of an entry with map error flag 
set: "
+                               "[device address=0x%016llx] [size=%llu 
bytes] "
+                               "[mapped with %s] [mapped as %s]\n",
+                       count, entry->dev_addr, entry->size,
+                       dir2name[entry->direction], type2name[entry->type]);
                 break;


-- 
Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley)
shuah.kh@...sung.com | (970) 672-0658
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