[Bug 1072278] Re: lsusb hangs forever

[Anton Fosselius]

The bug is still there in Ubuntu 16.04

strace lsusb

read(6, "MAJOR=189\nMINOR=128\nDEVNAME=bus/"..., 4096) = 126
read(6, "", 4096)                       = 0
read(6, "", 4096)                       = 0
close(6)                                = 0
getrandom("\210\215\f\212\365Aik\207\204b\t\25v?\330", 16, GRND_NONBLOCK) = 16
getrandom("\206<>\362?\3478W\266\251\370:9\0063\30", 16, GRND_NONBLOCK) = 16
open("/sys/bus/usb/devices/usb2/busnum", O_RDONLY) = 6
fstat(6, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
read(6, "2\n", 4096)                    = 2
close(6)                                = 0
open("/sys/bus/usb/devices/usb2/devnum", O_RDONLY) = 6
fstat(6, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
read(6, "1\n", 4096)                    = 2
close(6)                                = 0
open("/sys/bus/usb/devices/usb2/speed", O_RDONLY) = 6
fstat(6, {st_mode=S_IFREG|0444, st_size=4096, ...}) = 0
read(6, "480\n", 4096)                  = 4
close(6)                                = 0
open("/sys/bus/usb/devices/usb2/descriptors", O_RDONLY) = 6
read(6, 

but it does not get stuck forever, just a looong time. ~1 minute.
sometimes i get a "unable to mount Android" error notification window after several minutes. sometimes nothing. when lsusb is done after ~1 minute i wont see my phone listed.
Have tried several times on both ports on my laptop. 

hmm. while writing this post, my phone suddenly mounted and showed up in
lsusb.. hmm magic?

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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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