[PATCH 14/29] params: Add static key module param

Andi Kleen
2013-03-23T01:31:15Z

Add a module param type for uint static keys. Useful for
time critical flags.

Cc: rusty@rustcorp.co.au
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
include/linux/moduleparam.h | 6 ++++++
kernel/params.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index e3c41af..ac815d2 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -398,6 +398,12 @@ extern int param_set_bint(const char *val, const struct kernel_param *kp);
extern struct kernel_param_ops param_ops_percpu_uint;
#define param_check_percpu_uint(name, p) param_check_uint

+/* Static key module params. Useful for time critical flags. */
+struct static_key;
+extern struct kernel_param_ops param_ops_static_key;
+#define param_check_static_key(name, p) \
+ __param_check(name, p, struct static_key)
+
/**
* 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 1a8a1ca..68f9482 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -23,6 +23,7 @@
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/ctype.h>
+#include <linux/jump_label.h>

/* Protects all parameters, and incidentally kmalloced_param list. */
static DEFINE_MUTEX(param_lock);
@@ -527,6 +528,40 @@ struct kernel_param_ops param_ops_percpu_uint = {
};
EXPORT_SYMBOL(param_ops_percpu_uint);

+/* Static key module params. Like a bool, but allows patching the jumps. */
+
+/* Noone else should change */
+static int param_static_key_set(const char *val, const struct kernel_param *kp)
+{
+ static DEFINE_SPINLOCK(lock);
+ bool l;
+ struct static_key *key = (struct static_key *)(kp->arg);
+ int ret = strtobool(val, &l);
+
+ if (ret < 0)
+ return ret;
+ /* Work around racy static key interface */
+ spin_lock(&lock);
+ if (l && !atomic_read(&key->enabled))
+ static_key_slow_inc(key);
+ if (!l && atomic_read(&key->enabled))
+ static_key_slow_dec(key);
+ spin_unlock(&lock);
+ return ret;
+}
+
+static int param_static_key_get(char *buffer, const struct kernel_param *kp)
+{
+ struct static_key *key = kp->arg;
+ return sprintf(buffer, "%u", atomic_read(&key->enabled) > 0);
+}
+
+struct kernel_param_ops param_ops_static_key = {
+ .set = param_static_key_set,
+ .get = param_static_key_get,
+};
+EXPORT_SYMBOL(param_ops_static_key);
+
/* 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