This bug was fixed in the package linux - 4.8.0-34.36
---------------
linux (4.8.0-34.36) yakkety; urgency=low
[ Luis Henriques ]
* Release Tracking Bug
- LP: #1651800
* Miscellaneous Ubuntu changes
- SAUCE: Do not build the xr-usb-serial driver for s390
linux (4.8.0-33.35) yakkety; urgency=low
[ Thadeu Lima de Souza Cascardo ]
* Release Tracking Bug
- LP: #1651721
[ Luis Henriques ]
* crypto : tolerate new crypto hardware for z Systems (LP: #1644557)
- s390/zcrypt: Introduce CEX6 toleration
* Several new Asus laptops are missing touchpad support (LP: #1650895)
- HID: asus: Add i2c touchpad support
* Acer, Inc ID 5986:055a is useless after 14.04.2 installed. (LP: #1433906)
- uvcvideo: uvc_scan_fallback() for webcams with broken chain
* cdc_ether fills kernel log (LP: #1626371)
- cdc_ether: Fix handling connection notification
* Kernel Fixes to get TCMU File Backed Optical to work (LP: #1646204)
- SAUCE: target/user: Fix use-after-free of tcmu_cmds if they are expired
* CVE-2016-9756
- KVM: x86: drop error recovery in em_jmp_far and em_ret_far
* On boot excessive number of kworker threads are running (LP: #1649905)
- slub: move synchronize_sched out of slab_mutex on shrink
* Ethernet not work after upgrade from kernel 3.19 to 4.4 [10ec:8168]
(LP: #1648279)
- ACPI / blacklist: Make Dell Latitude 3350 ethernet work
* Ubuntu 16.10 netboot install fails with "Oops: Exception in kernel mode,
sig: 5 [#1] " (lpfc) (LP: #1648873)
- scsi: lpfc: fix oops/BUG in lpfc_sli_ringtxcmpl_put()
* CVE-2016-9793
- net: avoid signed overflows for SO_{SND|RCV}BUFFORCE
* [Hyper-V] Kernel panic not functional on 32bit Ubuntu 14.10, 15.04, and
15.10 (LP: #1400319)
- Drivers: hv: avoid vfree() on crash
* d-i is missing usb support for platforms that use the xhci-platform driver
(LP: #1625222)
- d-i initrd needs additional usb modules to support the merlin platform
* overlayfs no longer supports nested overlayfs mounts, but there is a fix
upstream (LP: #1647007)
- ovl: fix d_real() for stacked fs
* Yakkety: arm64: CONFIG_ARM64_ERRATUM_845719 isn't enabled (LP: #1647793)
- [Config] CONFIG_ARM64_ERRATUM_845719=y
* Ubuntu16.10 - EEH on BELL3 adapter fails to recover (serial/tty)
(LP: #1646857)
- serial: 8250_pci: Detach low-level driver during PCI error recovery
* Driver for Exar USB UART (LP: #1645591)
- SAUCE: xr-usb-serial: Driver for Exar USB serial ports
- SAUCE: xr-usb-serial: interface for switching modes
- SAUCE: cdc-acm: Exclude Exar USB serial ports
* [Bug] (Purley) x86/hpet: Reduce HPET counter read contention (LP: #1645928)
- x86/hpet: Reduce HPET counter read contention
* Need Alps upstream their new touchpad driver (LP: #1571530)
- Input: ALPS - add touchstick support for SS5 hardware
- Input: ALPS - handle 0-pressure 1F events
- Input: ALPS - allow touchsticks to report pressure
- Input: ALPS - set DualPoint flag for 74 03 28 devices
* CONFIG_NR_CPUS=256 is too low (LP: #1579205)
- [Config] Increase the NR_CPUS to 512 for amd64 to support systems with a
large number of cores.
-- Luis Henriques <[email protected]> Wed, 21 Dec 2016
16:20:08 +0000
** Changed in: linux (Ubuntu Yakkety)
Status: Fix Committed => Fix Released
** CVE added: http://www.cve.mitre.org/cgi-
bin/cvename.cgi?name=2016-9756
** CVE added: http://www.cve.mitre.org/cgi-
bin/cvename.cgi?name=2016-9793
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https://bugs.launchpad.net/bugs/1649905
Title:
On boot excessive number of kworker threads are running
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Yakkety:
Fix Released
Status in linux source package in Zesty:
Fix Released
Bug description:
[SRU REQUEST, Yakkety]
Ubuntu Yakkety 4.8 kernels have an excessive amount of kworker threads
running, this is especially noticeable on boot, one can easily have >
1000 kworker threads on a 4 CPU box.
Bisected this down to:
commit 81ae6d03952c1bfb96e1a716809bd65e7cd14360
Author: Vladimir Davydov <[email protected]>
Date: Thu May 19 17:10:34 2016 -0700
mm/slub.c: replace kick_all_cpus_sync() with synchronize_sched() in
kmem_cache_shrink()
[FIX]
The synchronize_sched calls seem to create all these excessive kworker
threads. This is fixed with upstream commit:
commit 89e364db71fb5e7fc8d93228152abfa67daf35fa
Author: Vladimir Davydov <[email protected]>
Date: Mon Dec 12 16:41:32 2016 -0800
slub: move synchronize_sched out of slab_mutex on shrink
synchronize_sched() is a heavy operation and calling it per each cache
owned by a memory cgroup being destroyed may take quite some time. What
is worse, it's currently called under the slab_mutex, stalling all works
doing cache creation/destruction.
Actually, there isn't much point in calling synchronize_sched() for each
cache - it's enough to call it just once - after setting cpu_partial for
all caches and before shrinking them. This way, we can also move it out
of the slab_mutex, which we have to hold for iterating over the slab
cache list.
[TEST CASE]
Without the fix, boot a Yakkety and count the number of kthreads:
ps -ef | grep kworker | wc -l
1034
With the fix, boot count the number kthreads and it will be
dramatically less:
ps -ef | grep kworker | wc -l
32
Since this touches the slub allocator and cgroups too, I have
regression tested this against the kernel-team autotest regression
tests to sanity check this fix. All seems OK.
Note: this only affects kernels from 4.7-rc1 through to 4.8
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