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Date: Tue, 14 Oct 2014 12:48:07 +0200
Message-ID: <CAAfyv34btPrqW5Z=wzdFi7e+tOYF6XPdxY6sKcMy0CBzBsVFqA@mail.gmail.com> (sfid-20141014_124812_718208_7170DF15)
Subject: Re: mwifiex_usb_submit_rx_urb: dev_alloc_skb failed when conected to 5GHz
From: Belisko Marek <marek.belisko@gmail.com>
To: James Cameron <quozl@laptop.org>
Cc: Amitkumar Karwar <akarwar@marvell.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	Avinash Patil <patila@marvell.com>
Content-Type: text/plain; charset=UTF-8
Sender: linux-wireless-owner@vger.kernel.org

Dear James Cameron,

On Tue, Oct 14, 2014 at 12:20 PM, James Cameron <quozl@laptop.org> wrote:
> On Tue, Oct 14, 2014 at 10:25:01AM +0200, Belisko Marek wrote:
>> Hi Amitkumar,
>>
>> On Tue, Oct 14, 2014 at 9:08 AM, Amitkumar Karwar <akarwar@marvell.com> wrote:
>> > Hi Marek,
>> >
>> > > I tried both (slightly modified as we're in 3.9 kernel) but
>> > > issue is still reproducible. My patch against 3.9 sources:
>> >
>> > Thanks a lot for the tests.
>> >
>> > > One thing which is not yet still clear to me why kernel console
>> > > is completely unresponsive when receiving packets in high
>> > > rates. When use iperf (on client) with -b40m it is OK but when
>> > > increase to -b100m then console is completely unresponsive until
>> > > iperf finish.
>> >
>> > Does the system recover when "-b100M" iperf is finished? Can we
>> > run iperf with "-b40M" later?  Do you see "dev_alloc_skb failed"
>> > messages in dmesg when console is unresponsive?
>> When we get "dev_alloc_skb failed" then interface is dead (cannot
>> ping ...) so no recovery is possible only system reboot.
>
> This symptom was familiar to me, but on sdio.c, which is very
> different code.
>
> I've had a brief look at usb.c and offer the following comments:
>
> - a list of six data endpoint urb is allocated in mwifiex_usb_rx_init,
>   because MWIFIEX_RX_DATA_URB is 6,
>
> - when data endpoint urb is submitted, a new skb is allocated, in
>   mwifiex_usb_submit_rx_urb, and this is the only source of
>   "dev_alloc_skb failed" message,
>
> - in normal situation, when data endpoint urb is complete, skb is
>   either freed or handed up to mwifiex_usb_recv, and the urb is
>   resubmitted, which causes a new skb to be allocated.
>
> - if "dev_alloc_skb failed" message appears, one data endpoint urb has
>   been lost and is not re-used,
>
> - if six "dev_alloc_skb failed" messages appear, the interface should
>   be dead for data receive only.
>
> Amitkumar mentioned this on 9th October; "corresponding URB won't get
> submitted".  I think this should be fixed; dev_alloc_skb should be
> harmless failure, please retry.
>
> I don't see why interface is dead with only one "dev_alloc_skb
> failed" message.
Maybe my description wasn't  not correct. I see 6 "dev_alloc_skb
failed" messages and then interface is dead
as you wrote.
>
>> I don't see  dev_alloc_skb failed when console is unresponsive.
>> >
>> > > Any other ideas
>> > > what to change to check? Thanks.
>> >
>> > Could you please share dmesg log with dynamic debug enabled (using
>> > attached script) captured when the problem occurs?
>> I tried to capture logs but when enable DYNAMIC_DEBUG I cannot
>> reproduce issue (running test > 30 minutes without allocation
>> failure).
>
> Yes, I've seen similar; turn on debugging, and timing critical bug
> goes away.
>
> Serial console?  If so, try turning it off, and logging to dmesg
> buffer only.
When turning off serial console how then I get kernel messages from
dmesg buffer?
>
> --
> James Cameron
> http://quozl.linux.org.au/

BR,

marek

-- 
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-------------------------------------------------
Marek Belisko - OPEN-NANDRA
Freelance Developer

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