linux-kernel - Re: [PATCH -mm 2/3] notifier error injection documentation

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Date:	Sun, 8 Jul 2012 17:03:04 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Akinobu Mita <akinobu.mita@...il.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Pavel Machek <pavel@....cz>, Greg KH <greg@...ah.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <michael@...erman.id.au>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH -mm 2/3] notifier error injection documentation

On Sunday, July 08, 2012, Akinobu Mita wrote:
> fault-injection-notifier-error-injection.patch in -mm tree adds
> notifier error injection.
> 
> This adds Documentation/fault-injection/notifier-error-inject.txt
> which describes its feature and usage examples.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> Cc: Pavel Machek <pavel@....cz>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Cc: Greg KH <greg@...ah.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <michael@...erman.id.au>
> Cc: Dave Jones <davej@...hat.com>

ACK for the PM part.

Thanks,
Rafael


> ---
>  .../fault-injection/notifier-error-inject.txt      |   99 ++++++++++++++++++++
>  1 file changed, 99 insertions(+)
>  create mode 100644 Documentation/fault-injection/notifier-error-inject.txt
> 
> 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.
> 

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