[Xenial][PATCH 0/1] Fix for libmbim-proxy using 100% CPU

Wen-chien Jesse Sung jesse.sung at canonical.com
Tue Nov 5 09:41:08 UTC 2019

BugLink: https://launchpad.net/bugs/1851347

== Impact ==
A Dell Edge Gateway 3002 user reported that `top` reports around
100% CPU usage for the libmbim-proxy process. Seen in at least
40% of their devices at some point during the last 6 months.
The CPU keeps high at ~100% days or weeks, but does return back
to normal without a reboot. The LTE connectivity is seemingly
still working as usual.

The issue starts after an EPIPE error in the syslogs:
cdc_mbim 1-3:1.12: nonzero urb status received: -EPIPE

== Fix ==
8fec9355a968 USB: cdc-wdm: ignore -EPIPE from GetEncapsulatedResponse
This has been in mainline kernel since 4.14.

== Testcase ==
Connect to the LTE network and see if libmbim-proxy uses 100% after
some point.

== Risk of Regression ==
Low, since
1. Already tested by original reporter and no issue found after
   more than a week (usually it fails twice in a week).
2. Ignoring -EPIPE is the default behavior after 4.14.

Bjørn Mork (1):
  USB: cdc-wdm: ignore -EPIPE from GetEncapsulatedResponse

 drivers/usb/class/cdc-wdm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)


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