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SubjectRe: Error: DMA: Out of SW-IOMMU space [was: External USB drives become unresponsive after few hours.]
From
I think the case is closed.
Now that I know it's not USB, but wireless driver, I looked through
the new k3.19.5's changelog and saw this:


commit b943e69d33fac1e5f6db57868e061096b0aae67a
Author: Larry Finger <Larry.Finger@lwfinger.net>
Date: Sat Mar 21 15:16:05 2015 -0500

rtlwifi: Fix IOMMU mapping leak in AP mode

commit be0b5e635883678bfbc695889772fed545f3427d upstream.

Transmission of an AP beacon does not call the TX interrupt service routine,
which usually does the cleanup. Instead, cleanup is handled in a tasklet
completion routine. Unfortunately, this routine has a serious bug
in that it does
not release the DMA mapping before it frees the skb, thus one
IOMMU mapping is
leaked for each beacon. The test system failed with no free IOMMU
mapping slots
approximately one hour after hostapd was used to start an AP.

This issue was reported and tested at
https://github.com/lwfinger/rtlwifi_new/issues/30.

Reported-and-tested-by: Kevin Mullican <kevin@mullican.com>
Cc: Kevin Mullican <kevin@mullican.com>
Signed-off-by: Shao Fu <shaofu@realtek.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


Looks very related, especially because my wireless card is also always
in AP mode, however I haven't been actually using it lately, so
probably that's why I didn't notice anything related to it (and kept
focused on USB), until I used dump_dma.

Well, due to my minimal knowledge regarding kernel's internals I can't
be 100% sure that this was it, but so far 3.19.5 is working stable
(uptime 6hrs and counting).

Thank you Konrad (and everyone else involved) for helping me out to
pinpoint the actual culprit.
Jake


On 18 April 2015 at 21:59, Dorian Gray <yourfavouritegod@gmail.com> wrote:
> On 18 April 2015 at 12:10, Dorian Gray <yourfavouritegod@gmail.com> wrote:
>> On 17 April 2015 at 22:06, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
>>> On Fri, Apr 17, 2015 at 05:14:20PM +0200, Dorian Gray wrote:
>>>> On 16 April 2015 at 20:42, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
>>>> > And easier way is to compile the kernel with CONFIG_DMA_API_DEBUG
>>>> > and then load the attached module.
>>>> >
>>>> > That should tell you who and what else is holding on the buffers.
>>>>
>>>> Ok, I have compiled 3.19.4 w/ CONFIG_DMA_API_DEBUG=y + the module you sent me.
>>>> Now, I'm not sure if I've done it right - I waited until the error
>>>> occured and then modprobe'd dump_dma.
>>>> I have attached the kernel log, but it tells me not much, if anything...
>>>
>>> The network driver is quite hungry for DMA. Did it do the same thing
>>> in the earlier kernels?
>>>
>>> Thanks.
>>>>
>>>> Thanks again.
>>>> Jake
>>>
>>>
>>
>> Yeah, you're right:
>>
>> # grep rtl8192se dump_dma_k3.19.4.log | wc -l
>> 6789
>> #
>> # grep rtl8192se dump_dma_k3.17.8.log | wc -l
>> 162
>> #
>>
>> So, wlan driver would be the real culprit then..?
>> I would have never thought...
>>
>> I guess I'm gonna test 3.19.4 once more (just to be sure) with
>> rtl8192se removed and see what happens.
>>
>> Thanks!
>> Jake
>
>
> [update]
>
> Ok, 6 hours of uptime (3.19.4 + blacklisted rtl8192se) and everything
> was fine...
> However, I was checking periodically and noticed that 'radeon' also
> tends to grow continuously over time, whereas ethernet driver sticks
> to, more or less, the same range:
>
> # uname -r
> 3.19.4
> #
> # grep -Eo 'radeon|r8169' L1.log | sort | uniq -c
> 62 r8169
> 4183 radeon
> #
> # grep -Eo 'radeon|r8169' L2.log | sort | uniq -c
> 33 r8169
> 5582 radeon
> #
> # grep -Eo 'radeon|r8169' L3.log | sort | uniq -c
> 54 r8169
> 7007 radeon
> #
> # grep -Eo 'radeon|r8169' L4.log | sort | uniq -c
> 49 r8169
> 7429 radeon
> #
> # grep -Eo 'radeon|r8169' L5.log | sort | uniq -c
> 34 r8169
> 9360 radeon
> #
>
> It doesn't grow that much in 3.17.8:
>
> # uname -r
> 3.17.8
> #
> # grep -Eo 'radeon|r8169|rtl8192se' L1.log | sort | uniq -c
> 265 r8169
> 1229 radeon
> 142 rtl8192se
> #
> # grep -Eo 'radeon|r8169|rtl8192se' L2.log | sort | uniq -c
> 187 r8169
> 3159 radeon
> 124 rtl8192se
> #
> # grep -Eo 'radeon|r8169|rtl8192se' L3.log | sort | uniq -c
> 41 r8169
> 1894 radeon
> 39 rtl8192se
> #
> # grep -Eo 'radeon|r8169|rtl8192se' L4.log | sort | uniq -c
> 64 r8169
> 3370 radeon
> 77 rtl8192se
> #
> # grep -Eo 'radeon|r8169|rtl8192se' L5.log | sort | uniq -c
> 52 r8169
> 2597 radeon
> 49 rtl8192se
> #
>
>
> Btw, at some point (3.19.4) I encounetered this:
> [21631.181909] DMA-API: debugging out of memory - disabling
>
> Jake


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