fault-injection: add CPU notifier error injection module

I used this module to test the series of modification to the cpu notifiers
code.

Example1: inject CPU offline error (-1 == -EPERM)

	# modprobe cpu-notifier-error-inject cpu_down_prepare_error=-1
	# echo 0 > /sys/devices/system/cpu/cpu1/online
	bash: echo: write error: Operation not permitted

Example2: inject CPU online error (-2 == -ENOENT)

	# modprobe cpu-notifier-error-inject cpu_up_prepare_error=-2
	# echo 1 > /sys/devices/system/cpu/cpu1/online
	bash: echo: write error: No such file or directory

[akpm@linux-foundation.org: fix Kconfig help text]
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 63 insertions, 0 deletions

diff --git a/lib/cpu-notifier-error-inject.c b/lib/cpu-notifier-error-inject.c
new file mode 100644
index 0000000..4dc2032
--- /dev/null
+++ b/lib/cpu-notifier-error-inject.c
@@ -0,0 +1,63 @@
+#include <linux/kernel.h>
+#include <linux/cpu.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+
+static int priority;
+static int cpu_up_prepare_error;
+static int cpu_down_prepare_error;
+
+module_param(priority, int, 0);
+MODULE_PARM_DESC(priority, "specify cpu notifier priority");
+
+module_param(cpu_up_prepare_error, int, 0644);
+MODULE_PARM_DESC(cpu_up_prepare_error,
+		"specify error code to inject CPU_UP_PREPARE action");
+
+module_param(cpu_down_prepare_error, int, 0644);
+MODULE_PARM_DESC(cpu_down_prepare_error,
+		"specify error code to inject CPU_DOWN_PREPARE action");
+
+static int err_inject_cpu_callback(struct notifier_block *nfb,
+				unsigned long action, void *hcpu)
+{
+	int err = 0;
+
+	switch (action) {
+	case CPU_UP_PREPARE:
+	case CPU_UP_PREPARE_FROZEN:
+		err = cpu_up_prepare_error;
+		break;
+	case CPU_DOWN_PREPARE:
+	case CPU_DOWN_PREPARE_FROZEN:
+		err = cpu_down_prepare_error;
+		break;
+	}
+	if (err)
+		printk(KERN_INFO "Injecting error (%d) at cpu notifier\n", err);
+
+	return notifier_from_errno(err);
+}
+
+static struct notifier_block err_inject_cpu_notifier = {
+	.notifier_call = err_inject_cpu_callback,
+};
+
+static int err_inject_init(void)
+{
+	err_inject_cpu_notifier.priority = priority;
+
+	return register_hotcpu_notifier(&err_inject_cpu_notifier);
+}
+
+static void err_inject_exit(void)
+{
+	unregister_hotcpu_notifier(&err_inject_cpu_notifier);
+}
+
+module_init(err_inject_init);
+module_exit(err_inject_exit);
+
+MODULE_DESCRIPTION("CPU notifier error injection module");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");