netdev - Re: [PATCH RFC net-next] bnx2x: avoid printing unnecessary messages during register dump

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Message-Id: <57ED3F1B.2040602@linux.vnet.ibm.com>
Date:   Thu, 29 Sep 2016 13:19:39 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...ux.vnet.ibm.com>
To:     David Miller <davem@...emloft.net>, ariel.elior@...gic.com,
        Yuval.Mintz@...gic.com
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH RFC net-next] bnx2x: avoid printing unnecessary messages
 during register dump



On 09/27/2016 11:43 PM, David Miller wrote:
> From: "Guilherme G. Piccoli" <gpiccoli@...ux.vnet.ibm.com>
> Date: Tue, 27 Sep 2016 15:33:54 -0300
> 
>> The bnx2x driver prints multiple error messages during register dump,
>> with "ethtool -d" for example. The driver even warn that many messages
>> might be seen during the register dump, but they are harmless. A typical
>> kernel log after register dump looks like this:
>>
>>   [9.375] bnx2x: [bnx2x_get_regs:987(net0)]Generating register dump. Might trigger harmless GRC timeouts
>>   [9.439] bnx2x: [bnx2x_attn_int_deasserted3:4342(net0)]LATCHED attention 0x04000000 (masked)
>>   [9.439] bnx2x: [bnx2x_attn_int_deasserted3:4346(net0)]GRC time-out 0x010580cd
>>   [...]
>>
>> The notation [...] means that some messages were supressed - in our
>> tests we saw 78 more "LATCHED attention" and "GRC time-out" messages,
>> supressed here.
>>
>> This patch avoid these messages to be printed on register dump instead
>> of just warn they are harmless.
>>
>> Signed-off-by: Guilherme G. Piccoli <gpiccoli@...ux.vnet.ibm.com>
> 
> Although "ethtool -d" is really a debugging facility, I still think that
> serious care should be placed into arranging what gets dumped in such
> a way that such access timeouts and errors are minimized.
> 

David, thanks for your comment. I confess I didn't understand your
statement quite well. You say we shouldn't dump registers that will
cause timeouts, that's it?

If yes, I guess this is a valid point. We will however loose some debug
information (as you mentioned, 'ethtool -d' is a debug facility). Now,
since I'm no expert in QLogic adapter hw/fw, I want to ask Yuval/Ariel
why those timeouts are hit anyway. Are they completely harmless?

In my understanding/opinion, hiding the messages entirely (as this patch
does) OR avoid the timeouts by disabling some registers' dump are both
better alternatives than the current behavior of the driver.

Thanks,



Guilherme