Re: All USB tools hang when one descriptor read fails and needs to timeout

[Troels Liebe Bentsen <troels@connectedcars.dk>]

Hi again,

Did a bit more testing and found another lock that would be nice to remove,
the /dev/bus/usb/$BUS/$DEV file for the hub is also locked:

Bus 003 Device 016: ID 1a40:0201 Terminus Technology Inc. FE 2.1 7-port Hub

strace lsusb -v
...
openat(AT_FDCWD, "/dev/bus/usb/003/016", O_RDWR|O_CLOEXEC...

The openat can not be canceled from userspace and even kill -9 won't stop
the process until the descriptor read times out.

Regards Troels

On Tue, 31 Jan 2023 at 21:56, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, Jan 31, 2023 at 03:41:08PM -0500, Alan Stern wrote:
> > On Tue, Jan 31, 2023 at 04:59:36PM +0100, Troels Liebe Bentsen wrote:
> > > On Fri, 27 Jan 2023 at 17:07, Alan Stern <stern@rowland.harvard.edu> wrote:
> > > > Now that I know the config descriptors won't get reallocated after all,
> > > > I can remove the locking from the descriptors file entirely.  A patch to
> > > > do this is below.  It ought to fix your problem.  Try it and see.
> > >
> > > Thank you very much, I built a new kernel with the patch and can confirm
> > > that it fixes my issue.
> > >
> > > Will the patch make it into any of the LTS kernels as it could seem like a
> > > bugfix depending on how you look at it or is it only destined mainline, fx. 6.2
> > > or 6.3?
> >
> > I don't know.  I will submit it for the -stable kernels, but the
> > decision on whether to accept it will be up to Greg KH.
>
> I'll backport it, as it can help out with systems as Troels said.  But
> will wait until 6.3-rc1 is out as this should get some testing.
>
> thanks,
>
> greg k-h