| 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. | |
| * 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 artificial 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. |