[Bug 1072278] Re: lsusb hangs forever

[Chronos]

Sorry for reviving an old bug report.

I have bumped into the same problem. Before I reboot, and loose the
posibility to run traces, I would like to attach them to help debug
this.


** Attachment added: "strace of lsusb when freezing and dmesg output"
   https://bugs.launchpad.net/ubuntu/+source/usbutils/+bug/1072278/+attachment/4308892/+files/khubd-crash.tar.gz

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https://bugs.launchpad.net/bugs/1072278

Title:
  lsusb hangs forever

Status in usbutils package in Ubuntu:
  Confirmed

Bug description:
  This is a spinoff of Bug 570049, as suggesgted by Dave Gilbert there.

  I've been experiencing the same issue on my Ubuntu 11.04 or 12.04 installations. Usb devices suddenly stops working after I plug/unplug some of them. I have a USB-Serial converte and an external SD-card reader and both seem to trigger the problem Only "workaround" is to reboot the system (which is not a solution, obviously). As it looks like from dmesg, the crash of khubd is at the root of the problem, and being a kernel thread can't be "restarted" other than rebooting.
   
  It looks like a common problem, across different distributions.

  Both the symptom (lsusb hanging) and what looks like the underlying
  cause are always the same: a crash of khubd kernel thread is always
  there, with a similar stack trace in every case, triggered by the same
  pattern: usb_stor_disconnect -> release_everything -> kthread_stop ->
  ...

  Also attaching a collection of logs from my system. Below the khubd
  stack trace from dmesg:

  42722.411019] Call Trace:
   [42722.411030] [<ffffffff815c85dd>] schedule_timeout+0x26d/0x2e0
   [42722.411038] [<ffffffff810576a3>] ? update_curr+0x103/0x210
   [42722.411044] [<ffffffff815c8099>] wait_for_common+0xd9/0x180
   [42722.411049] [<ffffffff8105f690>] ? default_wake_function+0x0/0x20
   [42722.411056] [<ffffffff815c821d>] wait_for_completion+0x1d/0x20
   [42722.411061] [<ffffffff810879e2>] kthread_stop+0x42/0xf0
   [42722.411068] [<ffffffffa02375fe>] release_everything+0x2e/0xb0 [usb_storage]
   [42722.411074] [<ffffffffa02384ca>] usb_stor_disconnect+0x2a/0x40 [usb_storage]
   [42722.411081] [<ffffffff8144464a>] usb_unbind_interface+0x5a/0x1a0
   [42722.411089] [<ffffffff813bb305>] __device_release_driver+0x75/0xe0
   [42722.411093] [<ffffffff813bb39d>] device_release_driver+0x2d/0x40
   [42722.411097] [<ffffffff813bae4b>] bus_r...

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