group.of.nepali.translators team mailing list archive

[Joseph Salisbury <joseph.salisbury@xxxxxxxxxxxxx>]

It appears the commit you mention has landed in upstream stable 4.4.25
as commit:

78c7b55 timekeeping: Fix __ktime_get_fast_ns() regression

The upstream stable commits up to version 4.4.30 have landed in Xenial
-proposed.

Would it be possible for you to test this latest kernel and post back if it resolves this bug?
See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. 

Thank you in advance!


** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Xenial)
       Status: New => Fix Committed

** Changed in: linux (Ubuntu)
       Status: Confirmed => Fix Committed

** Changed in: linux (Ubuntu)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu Xenial)
   Importance: Undecided => Medium

** Changed in: linux (Ubuntu)
     Assignee: (unassigned) => Joseph Salisbury (jsalisbury)

** Changed in: linux (Ubuntu Xenial)
     Assignee: (unassigned) => Joseph Salisbury (jsalisbury)

** Tags added: xenial

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https://bugs.launchpad.net/bugs/1645449

Title:
  Linux perf regression in 4.4.0-42 and newer

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed

Bug description:
  There is a regression in the 4.4.0-42 kernel update that is still
  present in the latest 4.4.0 update. I have verified that this appears
  in Ubuntu 16.04 and Ubuntu 14.04 (with ubuntu-xenial kernel installed)
  amd64. I also suspect this happens in default Ubuntu 16.10 kernel as
  well, but i have not tested.

  4.4.0-38 did not have this issue.

  in 4.4.0-42 and newer, perf records incorrect timestamps which can be
  verified by running this command:

  $ perf record -a -e sched:sched_-k CLOCK_MONOTONIC switch stress -c 10000 -t 10
  stress: info: [25560] dispatching hogs: 10000 cpu, 0 io, 0 vm, 0 hdd
  stress: info: [25560] successful run completed in 6s
  [ perf record: Woken up 16 times to write data ]
  Warning:
  78487 out of order events recorded.

  
  Note that the warning about out of order events is a symptom of this problem and is not expected to happen. This does not happen(correct behavior) if i run 4.4.0-38 and older, or if i run a fully patched upstream 4.4.35 kernel instead.

  
  This regression has already been fixed upstream but has not been included in ubuntu-xenial  kernel yet. 

  Upstream fix is here:
  https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/?id=78c7b55b362e868e529ab6579134708fcf5539dd

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