fault-injection: notifier error injection

This patchset provides kernel modules that can be used to test the error
handling of notifier call chain failures by injecting artifical errors to
the following notifier chain callbacks.

 * CPU notifier
 * PM notifier
 * memory hotplug notifier
 * powerpc pSeries reconfig notifier

Example: 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

The patchset also adds cpu and memory hotplug tests to
tools/testing/selftests These tests first do simple online and offline
test and then do fault injection tests if notifier error injection
module is available.

This patch:

The 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.

This adds common basic functions to define which type of events can be
fail and to initialize the debugfs interface to control what error code
should be returned and which event should be failed.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Greg KH <greg@kroah.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 99 insertions, 0 deletions

diff --git a/Documentation/fault-injection/notifier-error-inject.txt b/Documentation/fault-injection/notifier-error-inject.txt
new file mode 100644
index 0000000..c83526c
--- /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.