Notifier error injection

Notifier error injection provides the ability to inject artificial errors to specified notifier chain callbacks. It is useful to test the error handling of notifier call chain failures which is rarely executed. There are kernel modules that can be used to test the following notifiers.

PM notifier
Memory hotplug notifier
powerpc pSeries reconfig notifier
Netdevice notifier

PM notifier error injection module

This feature is controlled through debugfs interface

/sys/kernel/debug/notifier-error-inject/pm/actions/<notifier event>/error

Possible PM notifier events to be failed are:

PM_HIBERNATION_PREPARE
PM_SUSPEND_PREPARE
PM_RESTORE_PREPARE

Example: Inject PM suspend error (-12 = -ENOMEM)::

# cd /sys/kernel/debug/notifier-error-inject/pm/
# echo -12 > actions/PM_SUSPEND_PREPARE/error
# echo mem > /sys/power/state
bash: echo: write error: Cannot allocate memory

Memory hotplug notifier error injection module

This feature is controlled through debugfs interface

/sys/kernel/debug/notifier-error-inject/memory/actions/<notifier event>/error

Possible memory notifier events to be failed are:

MEM_GOING_ONLINE
MEM_GOING_OFFLINE

Example: Inject memory hotplug offline error (-12 == -ENOMEM)::

# cd /sys/kernel/debug/notifier-error-inject/memory
# echo -12 > actions/MEM_GOING_OFFLINE/error
# echo offline > /sys/devices/system/memory/memoryXXX/state
bash: echo: write error: Cannot allocate memory

powerpc pSeries reconfig notifier error injection module

This feature is controlled through debugfs interface

/sys/kernel/debug/notifier-error-inject/pSeries-reconfig/actions/<notifier event>/error

Possible pSeries reconfig notifier events to be failed are:

PSERIES_RECONFIG_ADD
PSERIES_RECONFIG_REMOVE
PSERIES_DRCONF_MEM_ADD
PSERIES_DRCONF_MEM_REMOVE

Netdevice notifier error injection module

This feature is controlled through debugfs interface

/sys/kernel/debug/notifier-error-inject/netdev/actions/<notifier event>/error

Netdevice notifier events which can be failed are:

NETDEV_REGISTER
NETDEV_CHANGEMTU
NETDEV_CHANGENAME
NETDEV_PRE_UP
NETDEV_PRE_TYPE_CHANGE
NETDEV_POST_INIT
NETDEV_PRECHANGEMTU
NETDEV_PRECHANGEUPPER
NETDEV_CHANGEUPPER

Example: Inject netdevice mtu change error (-22 == -EINVAL)::

# cd /sys/kernel/debug/notifier-error-inject/netdev
# echo -22 > actions/NETDEV_CHANGEMTU/error
# ip link set eth0 mtu 1024
RTNETLINK answers: Invalid argument

For more usage examples

There are tools/testing/selftests using the notifier error injection features for CPU and memory notifiers.

tools/testing/selftests/cpu-hotplug/cpu-on-off-test.sh
tools/testing/selftests/memory-hotplug/mem-on-off-test.sh

These scripts first do simple online and offline tests and then do fault injection tests if notifier error injection module is available.