Bug#845658: linux: Bad(?) USB device crashes USB system
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Hello Paul,
On Sat, 2016-11-26 at 17:28 +0100, Paul Menzel wrote:
>
> > I've had similar issues on my box. I worked with the USB folks but really
> > couldn't come up with a convincing resolution.
>
> Is that discussion public? Could you please give me the thread subject
> or URL?
>
Yes. Part of it we root caused. But not what was bothering me. The conclusion
was that I have a broken device. I'm not convinced, given that under Windows it
works perfect, but then I don't have the resource to challenge the statement.
You can access the thread at:
https://www.mail-archive.com/linux-usb@vger.kernel.org/msg79514.html
It should lead you to the rest of the thread.
> > Nov 25 18:46:54 learner kernel: usb 2-4: Product: USB2.0-CRW
> > Nov 25 18:46:54 learner kernel: usb 2-4: Manufacturer: Generic
>
> Are you able to reproduce the crash?
>
I guess you mean the erratic USB disconnects. Yes. And once they trigger, the
erratic USB device vanishes from the `lsusb` listing.
> > But what do you mean by "crashed" ? The particular USB port becomes
> > inaccessible.
>
> Indeed, it does not crash the Linux kernel, but the USB port is not
> usable anymore.
>
Yes. IN my case, it is not the port which is reflecting the disconnects, but
rather one of the USB devices (SDCard Reader). But I do very very occasionally
get other devices also to reset, so it could be a much more severe problem, yet
to root cause.
> > The kernel still works, maybe inefficient, but it does not crash
> > the kernel.
>
> Indeed. What do you mean by inefficient?
>
Well. The USB device resets very frequently, like every 10 seconds. This overall
has the side-effect of drawing too much power on my laptop.
> I noticed, that `uptime`, `top`, or `htop` display a high usage. For
> each `lsusb` I started (for debugging) it looks like one CPU core gets
> used 100 %?
>
> ```
> $ uptime
> 17:17:37 up x days, 9:34, x users, load average: 7,29, 7,64, 7,82
> ```
>
I haven't monitored this aspect, but it is possible that this too may be
happening, though for a small amount of time.
> I can find no processes in `htop` or `top` using that much CPU. I have
> no idea how to find out what is causing this, but I’d guess it’s
> something in the Linux kernel.
>
Yes. Because it is in the kernel. If it were related to I/O, you may have
noticed per-BDI threads, but in this case, these are device resets and
disconnects. So there's not much to capture in process listings.
You could gather some additional information from udev, because your USB
disconnects are equivalent to physical device plug/unplug, which triggers in the
hotplug mechanism. At least, it may tell you how frequent your disconnect errors
are happening. And if you have heavy (USB) rules processing, then it could be
the cause of your sudden load increase.
I hope this information helps you.
- --
Ritesh Raj Sarraf | http://people.debian.org/~rrs
Debian - The Universal Operating System
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