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Diffstat (limited to 'Documentation/fault-injection/notifier-error-inject.txt')
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diff --git a/Documentation/fault-injection/notifier-error-inject.txt b/Documentation/fault-injection/notifier-error-inject.txt new file mode 100644 index 00000000000..c83526c364e --- /dev/null +++ b/Documentation/fault-injection/notifier-error-inject.txt @@ -0,0 +1,99 @@ +Notifier error injection +======================== + +Notifier error injection provides the ability to inject artifical 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. + + * CPU notifier + * PM notifier + * Memory hotplug notifier + * powerpc pSeries reconfig notifier + +CPU notifier error injection module +----------------------------------- +This feature can be used to test the error handling of the CPU notifiers by +injecting artifical errors to CPU notifier chain callbacks. + +If the notifier call chain should be failed with some events notified, write +the error code to debugfs interface +/sys/kernel/debug/notifier-error-inject/cpu/actions/<notifier event>/error + +Possible CPU notifier events to be failed are: + + * CPU_UP_PREPARE + * CPU_UP_PREPARE_FROZEN + * CPU_DOWN_PREPARE + * CPU_DOWN_PREPARE_FROZEN + +Example1: Inject CPU offline error (-1 == -EPERM) + + # cd /sys/kernel/debug/notifier-error-inject/cpu + # echo -1 > actions/CPU_DOWN_PREPARE/error + # echo 0 > /sys/devices/system/cpu/cpu1/online + bash: echo: write error: Operation not permitted + +Example2: inject CPU online error (-2 == -ENOENT) + + # echo -2 > actions/CPU_UP_PREPARE/error + # echo 1 > /sys/devices/system/cpu/cpu1/online + bash: echo: write error: No such file or directory + +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 + +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/on-off-test.sh + * tools/testing/selftests/memory-hotplug/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. |