LXR linux/Documentation/fault-injection/notifier-error-inject.rst

   1Notifier error injection
   2========================
   3
   4Notifier error injection provides the ability to inject artificial errors to
   5specified notifier chain callbacks. It is useful to test the error handling of
   6notifier call chain failures which is rarely executed.  There are kernel
   7modules that can be used to test the following notifiers.
   8
   9 * PM notifier
  10 * Memory hotplug notifier
  11 * powerpc pSeries reconfig notifier
  12 * Netdevice notifier
  13
  14PM notifier error injection module
  15----------------------------------
  16This feature is controlled through debugfs interface
  17
  18  /sys/kernel/debug/notifier-error-inject/pm/actions/<notifier event>/error
  19
  20Possible PM notifier events to be failed are:
  21
  22 * PM_HIBERNATION_PREPARE
  23 * PM_SUSPEND_PREPARE
  24 * PM_RESTORE_PREPARE
  25
  26Example: Inject PM suspend error (-12 = -ENOMEM)::
  27
  28        # cd /sys/kernel/debug/notifier-error-inject/pm/
  29        # echo -12 > actions/PM_SUSPEND_PREPARE/error
  30        # echo mem > /sys/power/state
  31        bash: echo: write error: Cannot allocate memory
  32
  33Memory hotplug notifier error injection module
  34----------------------------------------------
  35This feature is controlled through debugfs interface
  36
  37  /sys/kernel/debug/notifier-error-inject/memory/actions/<notifier event>/error
  38
  39Possible memory notifier events to be failed are:
  40
  41 * MEM_GOING_ONLINE
  42 * MEM_GOING_OFFLINE
  43
  44Example: Inject memory hotplug offline error (-12 == -ENOMEM)::
  45
  46        # cd /sys/kernel/debug/notifier-error-inject/memory
  47        # echo -12 > actions/MEM_GOING_OFFLINE/error
  48        # echo offline > /sys/devices/system/memory/memoryXXX/state
  49        bash: echo: write error: Cannot allocate memory
  50
  51powerpc pSeries reconfig notifier error injection module
  52--------------------------------------------------------
  53This feature is controlled through debugfs interface
  54
  55  /sys/kernel/debug/notifier-error-inject/pSeries-reconfig/actions/<notifier event>/error
  56
  57Possible pSeries reconfig notifier events to be failed are:
  58
  59 * PSERIES_RECONFIG_ADD
  60 * PSERIES_RECONFIG_REMOVE
  61 * PSERIES_DRCONF_MEM_ADD
  62 * PSERIES_DRCONF_MEM_REMOVE
  63
  64Netdevice notifier error injection module
  65----------------------------------------------
  66This feature is controlled through debugfs interface
  67
  68  /sys/kernel/debug/notifier-error-inject/netdev/actions/<notifier event>/error
  69
  70Netdevice notifier events which can be failed are:
  71
  72 * NETDEV_REGISTER
  73 * NETDEV_CHANGEMTU
  74 * NETDEV_CHANGENAME
  75 * NETDEV_PRE_UP
  76 * NETDEV_PRE_TYPE_CHANGE
  77 * NETDEV_POST_INIT
  78 * NETDEV_PRECHANGEMTU
  79 * NETDEV_PRECHANGEUPPER
  80 * NETDEV_CHANGEUPPER
  81
  82Example: Inject netdevice mtu change error (-22 == -EINVAL)::
  83
  84        # cd /sys/kernel/debug/notifier-error-inject/netdev
  85        # echo -22 > actions/NETDEV_CHANGEMTU/error
  86        # ip link set eth0 mtu 1024
  87        RTNETLINK answers: Invalid argument
  88
  89For more usage examples
  90-----------------------
  91There are tools/testing/selftests using the notifier error injection features
  92for CPU and memory notifiers.
  93
  94 * tools/testing/selftests/cpu-hotplug/on-off-test.sh
  95 * tools/testing/selftests/memory-hotplug/on-off-test.sh
  96
  97These scripts first do simple online and offline tests and then do fault
  98injection tests if notifier error injection module is available.
  99