I'm changing the status of the "linux (Ubuntu)" entry - which represents
'focal' the current release in development - to Fix Released, since patch
"s390/idle: fix cpu idle time calculation" with commit ID "3d7efa4" landed in
focal with the update of focal's kernel to 5.4 (5.4.0.9.11 as of today).
This patch is in:
Ubuntu-5.4-5.4.0-10.13
Ubuntu-5.4-5.4.0-11.14
Ubuntu-5.4.0-8.11
Ubuntu-5.4.0-9.12
** Changed in: linux (Ubuntu)
Status: Confirmed => Fix Released
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https://bugs.launchpad.net/bugs/1854059
Title:
[UBUNTU] kernel: cpu idle time calculation
Status in Ubuntu on IBM z Systems:
Fix Committed
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Bionic:
Fix Committed
Status in linux source package in Disco:
Fix Committed
Status in linux source package in Eoan:
Fix Committed
Bug description:
Description: kernel: cpu idle time calculation
Symptom: The cpu idle time reported within /proc/stat as well as in
/sys/devices/system/cpu/cpuX/idle_time_us sometimes may
show incorrect values.
Problem: The kernel tries to figure out when a cpu entered idle
by accessing its per-cpu data structure. There is an
ordering problem: if a remote cpu has an idle_enter
value which is not zero, and an idle_exit value which
is zero, it is assumed it is idle since "now". The
"now" timestamp however is taken before the idle_enter
value is read.
This in turn means that "now" can be smaller than
idle_enter of the remote cpu. Unconditionally
subtracting idle_enter from "now" can thus lead to a
negative value (aka large unsigned value).
Solution: Move the get_tod_clock() invocation.
Upstream-ID:
https://github.com/torvalds/linux/commit/3d7efa4edd07be5c5c3ffa95ba63e97e070e1f3f
Patch tagged as "stable".
Tracking the integration of this patch in the relevant distros..
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