Bug ID: 202679
           Summary: disabling secondary CPU hangs / system fails to
                    suspend with kernel 4.19+ on Lenovo ThinkPad X1 Carbon
           Product: ACPI
           Version: 2.5
    Kernel Version: 4.19
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Power-Sleep-Wake
        Regression: Yes

Created attachment 281343
dmesg from failed suspend attempt with 4.20.6 and wifi and LTE disabled

Starting with kernel 4.19 my Lenovo ThinkPad X1 Carbon 5th fails to suspend to
When closing the lid or executing "systemctl suspend" the screen goes black and
the status led starts to blink rapidly (just like when power is plugged in).
The keyboard lights can still be toggled using Fn+space, so the firmware
appears to be (partly) alive.

When I execute
> echo core > /sys/power/pm_test
> echo processors > /sys/power/pm_test
and then
> echo mem > /sys/power/state
the system immediately goes blank and freezes just like when I really try to
activate suspend.

If I try to execute
# chcpu -d 1,2,3
# echo 0 > /sys/devices/system/cpu/cpu1/online
the command blocks, while the system itself remains (mostly) usable.
Unfortunately, no message whatsoever is shown in the kernel logs. Also, reboot
or poweroff no longer works and the system needs a hard reset. :(

I have bisected the kernel and found the culprit (or at least something, that
appears to trigger the bad behavior):

[be45bf5395e0886a93fc816bbe41a008ec2e42e2] watchdog/softlockup: Fix
cpu_stop_queue_work() double-queue bug
be45bf5395e0886a93fc816bbe41a008ec2e42e2 is the first bad commit
commit be45bf5395e0886a93fc816bbe41a008ec2e42e2
Author: Peter Zijlstra <>
Date:   Fri Jul 13 12:42:08 2018 +0200

    watchdog/softlockup: Fix cpu_stop_queue_work() double-queue bug

    When scheduling is delayed for longer than the softlockup interrupt
    period it is possible to double-queue the cpu_stop_work, causing list

    Cure this by adding a completion to track the cpu_stop_work's

    Reported-by: kernel test robot <>
    Tested-by: Rong Chen <>
    Signed-off-by: Peter Zijlstra (Intel) <>
    Cc: Linus Torvalds <>
    Cc: Peter Zijlstra <>
    Cc: Thomas Gleixner <>
    Fixes: 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads
with cpu_stop_work")
    Signed-off-by: Ingo Molnar <>

:040000 040000 6aca2dbb84bc33fe442b18b3d0a135c27adff7b9
2710af12d32e4b98df07768716689b213bce45fc M      kernel

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