[PATCH 13/29] params: Add a per cpu module param type

Andi Kleen
2013-03-23T01:28:09Z

This is mainly useful for simple statistic counters.
Essentially read-only, writing only clears.

Cc: rusty@rustcorp.co.au
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
include/linux/moduleparam.h | 4 ++++
kernel/params.c | 28 ++++++++++++++++++++++++++++
2 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 137b419..e3c41af 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -394,6 +394,10 @@ extern int param_set_bint(const char *val, const struct kernel_param *kp);
#define param_get_bint param_get_int
#define param_check_bint param_check_int

+/* A per cpu read-only unsigned integer. Useful for counters. */
+extern struct kernel_param_ops param_ops_percpu_uint;
+#define param_check_percpu_uint(name, p) param_check_uint
+
/**
* module_param_array - a parameter which is an array of some type
* @name: the name of the array variable
diff --git a/kernel/params.c b/kernel/params.c
index ed35345..1a8a1ca 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -499,6 +499,34 @@ struct kernel_param_ops param_ops_string = {
};
EXPORT_SYMBOL(param_ops_string);

+/* Per CPU read only module param. */
+
+static int param_percpu_uint_set(const char *val, const struct kernel_param *kp)
+{
+ int cpu;
+
+ /* just clear on any write */
+ for_each_possible_cpu(cpu)
+ *per_cpu_ptr((unsigned * __percpu)(kp->arg), cpu) = 0;
+ return 0;
+}
+
+static int param_percpu_uint_get(char *buffer, const struct kernel_param *kp)
+{
+ int cpu;
+ unsigned count = 0;
+
+ for_each_possible_cpu(cpu)
+ count += *per_cpu_ptr((unsigned * __percpu)(kp->arg), cpu);
+ return sprintf(buffer, "%u", count);
+}
+
+struct kernel_param_ops param_ops_percpu_uint = {
+ .set = param_percpu_uint_set,
+ .get = param_percpu_uint_get,
+};
+EXPORT_SYMBOL(param_ops_percpu_uint);
+
/* sysfs output in /sys/modules/XYZ/parameters/ */
#define to_module_attr(n) container_of(n, struct module_attribute, attr)
#define to_module_kobject(n) container_of(n, struct module_kobject, kobj)
--
1.7.7.6