https://bugzilla.kernel.org/show_bug.cgi?id=169241

            Bug ID: 169241
           Summary: AC to battery causes extreme load, many kworker
                    threads in D state
           Product: ACPI
           Version: 2.5
    Kernel Version: 4.4.0, 4.6.3
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Power-Battery
          Assignee: acpi_power-batt...@kernel-bugs.osdl.org
          Reporter: spambox+kernel...@thisblueroom.net
        Regression: No

SYNOPSIS

Most of the time, disconnecting a 2008 Macbook from AC, or reconnecting it to
AC, will cause hundreds of kworker threads to be spawned, driving up system
load to levels where a GUI may become unusable. CPU and iowait is low. kworker
threads are in D state. 'powertop' shows increased numbers of ACPI interrupts,
and acpi_ec_event_processor and acpi_os_execute_deferred very high ms/s figures
in the Usage column.

This is occurring on Lubuntu 16.04. The bug is present in the 4.4.0
distribution kernel and in kernel 4.6.3-yakkety from the Ubuntu kernel PPA.
Booting with acpi=off renders critical portions of the system unusable.

See also: https://ubuntuforums.org/showthread.php?t=2335053&p=13544491


RELATED INFO

'top':
top - 21:29:22 up 1 day, 5:57, 2 users, load average: 223.67, 179.10, 166.01
Tasks: 448 total, 1 running, 447 sleeping, 0 stopped, 0 zombie
%Cpu(s): 4.3 us, 1.0 sy, 0.0 ni, 94.5 id, 0.2 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 4011084 total, 557060 free, 2009348 used, 1444676 buff/cache
KiB Swap: 2999804 total, 2607704 free, 392100 used. 1574160 avail Mem 


$ ps ax | grep kworker | wc -l
271


$ ps -e -o state,pid,cmd | grep ^D | grep kworker | wc -l
257


'powertop' before power source change:
Summary: 294.0 wakeups/second,  2.1 GPU ops/seconds, 0.0 VFS ops/sec and 6.7%
CPU use
                Usage       Events/s    Category       Description
            100.0%                      Device         Audio codec hwC0D0:
Realtek
              6.0 ms/s      54.1        Process       
/usr/lib/chromium-browser/chromium-browser --enable-pinch
             38.0 ms/s      48.5        Process       
/usr/lib/chromium-browser/chromium-browser --type=renderer --enable-pinch
--enable-features=D
            362.1 ┬Ás/s      29.8        kWork          dbs_timer
              1.6 ms/s      27.3        Interrupt      [9] acpi


'powertop' two refreshes after power source change:

Summary: 300.8 wakeups/second,  3.8 GPU ops/seconds, 0.0 VFS ops/sec and
1084.8% CPU use
                Usage       Events/s    Category       Description
             9627 ms/s       9.9        kWork          acpi_ec_event_processor
             1138 ms/s      16.3        kWork          acpi_os_execute_deferred
             13.8 ms/s     236.5        Interrupt      [9] acpi
            100.0%                      Device         Audio codec hwC0D0:
Realtek

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