Documentation/fault-injection/notifier-error-inject.txt

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