Re: "usbip: Implement SG support to vhci-hcd and stub driver" causes a deadlock

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Fri, Dec 06, 2019 at 02:12:08PM -0700, Shuah Khan wrote:
> On 12/6/19 1:57 PM, Marek Marczykowski-Górecki wrote:
> > On Fri, Dec 06, 2019 at 03:50:58PM +0900, Suwan Kim wrote:
> > > On Fri, Dec 06, 2019 at 04:24:06AM +0100, Marek Marczykowski-Górecki wrote:
> > > > Hello,
> > > > 
> > > > I've hit an issue with recent 4.19 and 5.4 kernels. In short: if I
> > > > connect Yubikey 4 and use its CCID interface (for example `ykman oath
> > > > list` command), the client side hangs (100% reliably). After 60s I get a
> > > > message that a CPU hangs waiting for a spinlock (see below).
> > > > 
> > > > I've bisected it to a ea44d190764b4422af ("usbip: Implement SG support
> > > > to vhci-hcd and stub driver") commit. Which indeed is also backported to
> > > > 4.19.
> > > > 
> > > > Any idea what is going on here? I can easily provide more information,
> > > > if you tell me how to get it.
> > > > 
> > > 
> > > Hi,
> > > 
> > > Thanks for reporting. Could you turn on lockdep and USBIP_DEBUG
> > > in kernel config and send dmesg log? It will be helpful to figure
> > > out lock dependency in vhci_hcd.
> > 
> > Hmm, I've tried, but I don't see much more information there (see
> > below). I've just enabled PROVE_LOCKING and USBIP_DEBUG. Do I need to do
> > anything more, like some boot option?
> > 
> > Also, this one (as the previous one) is from 4.19.84. Interestingly, on
> > 4.19.87 I don't get the message at all.
> > 
> > Hmm, I've done also another test: got 4.19.84 with "usbip: Implement SG
> > support to vhci-hcd and stub driver" reverted and it still hangs...
> > 
> > I'm going for another bisect round (4.19.81 works, 4.19.84 doesn't).
> 
> Does 4.19.82 work?

Yes, it does, or at least something after 4.19.82 works (9da271c1c).

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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