* [PATCH 1/2] params: Add a per cpu module param type
@ 2014-08-19 15:16 Andi Kleen
2014-08-19 15:16 ` [PATCH 2/2] params: Add static key module param Andi Kleen
2014-08-19 18:07 ` [PATCH 1/2] params: Add a per cpu module param type Rusty Russell
0 siblings, 2 replies; 3+ messages in thread
From: Andi Kleen @ 2014-08-19 15:16 UTC (permalink / raw
To: linux-kernel; +Cc: Andi Kleen, rusty
From: Andi Kleen <ak@linux.intel.com>
This is mainly useful for simple statistic counters.
Essentially read-only, writing only clears.
Cc: rusty@rustcorp.com.au
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
include/linux/moduleparam.h | 4 ++++
kernel/params.c | 28 ++++++++++++++++++++++++++++
2 files changed, 32 insertions(+)
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index 494f99e..d019ad2 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -408,6 +408,10 @@ 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 34f5270..700badd 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)
--
1.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH 2/2] params: Add static key module param
2014-08-19 15:16 [PATCH 1/2] params: Add a per cpu module param type Andi Kleen
@ 2014-08-19 15:16 ` Andi Kleen
2014-08-19 18:07 ` [PATCH 1/2] params: Add a per cpu module param type Rusty Russell
1 sibling, 0 replies; 3+ messages in thread
From: Andi Kleen @ 2014-08-19 15:16 UTC (permalink / raw
To: linux-kernel; +Cc: Andi Kleen, rusty
From: Andi Kleen <ak@linux.intel.com>
Add a module param type for static keys. Useful for
time critical flags.
The basic jump_label interface is racy for boolean settings,
because checking and changing is not atomic, so we use an
additional lock
Open: should use deferred keys? But as it's only root changeable
changes should be very rare. Would need some changes to jump
labels.
Cc: rusty@rustcorp.com.au
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
include/linux/moduleparam.h | 6 ++++++
kernel/params.c | 35 +++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+)
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index d019ad2..30cdad8 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -412,6 +412,12 @@ 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 700badd..d176ae8 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)
--
1.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 1/2] params: Add a per cpu module param type
2014-08-19 15:16 [PATCH 1/2] params: Add a per cpu module param type Andi Kleen
2014-08-19 15:16 ` [PATCH 2/2] params: Add static key module param Andi Kleen
@ 2014-08-19 18:07 ` Rusty Russell
1 sibling, 0 replies; 3+ messages in thread
From: Rusty Russell @ 2014-08-19 18:07 UTC (permalink / raw
To: Andi Kleen, linux-kernel; +Cc: Andi Kleen
Andi Kleen <andi@firstfloor.org> writes:
> From: Andi Kleen <ak@linux.intel.com>
>
> This is mainly useful for simple statistic counters.
> Essentially read-only, writing only clears.
Nice...
> +#define param_check_percpu_uint(name, p) param_check_uint
This is wrong; will it even compile? It should also do the __percpu
annotation so hopefully sparse will catch any misuses, eg:
#define param_check_percpu_uint(name, p) \
__param_check(name, p, __percpu unsigned int)
The rest looks good, but I'll need a user :)
Cheers,
Rusty.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-08-19 18:11 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2014-08-19 15:16 [PATCH 1/2] params: Add a per cpu module param type Andi Kleen
2014-08-19 15:16 ` [PATCH 2/2] params: Add static key module param Andi Kleen
2014-08-19 18:07 ` [PATCH 1/2] params: Add a per cpu module param type Rusty Russell
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