static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]()

So here's a boot tested patch on top of Jason's series that does
all the cleanups I talked about and turns jump labels into a
more intuitive to use facility. It should also address the
various misconceptions and confusions that surround jump labels.

Typical usage scenarios:

        #include <linux/static_key.h>

        struct static_key key = STATIC_KEY_INIT_TRUE;

        if (static_key_false(&key))
                do unlikely code
        else
                do likely code

Or:

        if (static_key_true(&key))
                do likely code
        else
                do unlikely code

The static key is modified via:

        static_key_slow_inc(&key);
        ...
        static_key_slow_dec(&key);

The 'slow' prefix makes it abundantly clear that this is an
expensive operation.

I've updated all in-kernel code to use this everywhere. Note
that I (intentionally) have not pushed through the rename
blindly through to the lowest levels: the actual jump-label
patching arch facility should be named like that, so we want to
decouple jump labels from the static-key facility a bit.

On non-jump-label enabled architectures static keys default to
likely()/unlikely() branches.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: a.p.zijlstra@chello.nl
Cc: mathieu.desnoyers@efficios.com
Cc: davem@davemloft.net
Cc: ddaney.cavm@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20120222085809.GA26397@elte.hu
Signed-off-by: Ingo Molnar <mingo@elte.hu>

4 files changed, 18 insertions, 18 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 115dee1d985d..da7ce7f0e566 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -134,7 +134,7 @@
 #include <linux/inetdevice.h>
 #include <linux/cpu_rmap.h>
 #include <linux/net_tstamp.h>
-#include <linux/jump_label.h>
+#include <linux/static_key.h>
 #include <net/flow_keys.h>
 
 #include "net-sysfs.h"
@@ -1441,11 +1441,11 @@ int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
 }
 EXPORT_SYMBOL(call_netdevice_notifiers);
 
-static struct jump_label_key netstamp_needed __read_mostly;
+static struct static_key netstamp_needed __read_mostly;
 #ifdef HAVE_JUMP_LABEL
-/* We are not allowed to call jump_label_dec() from irq context
+/* We are not allowed to call static_key_slow_dec() from irq context
  * If net_disable_timestamp() is called from irq context, defer the
- * jump_label_dec() calls.
+ * static_key_slow_dec() calls.
  */
 static atomic_t netstamp_needed_deferred;
 #endif
@@ -1457,12 +1457,12 @@ void net_enable_timestamp(void)
 
 	if (deferred) {
 		while (--deferred)
-			jump_label_dec(&netstamp_needed);
+			static_key_slow_dec(&netstamp_needed);
 		return;
 	}
 #endif
 	WARN_ON(in_interrupt());
-	jump_label_inc(&netstamp_needed);
+	static_key_slow_inc(&netstamp_needed);
 }
 EXPORT_SYMBOL(net_enable_timestamp);
 
@@ -1474,19 +1474,19 @@ void net_disable_timestamp(void)
 		return;
 	}
 #endif
-	jump_label_dec(&netstamp_needed);
+	static_key_slow_dec(&netstamp_needed);
 }
 EXPORT_SYMBOL(net_disable_timestamp);
 
 static inline void net_timestamp_set(struct sk_buff *skb)
 {
 	skb->tstamp.tv64 = 0;
-	if (static_branch(&netstamp_needed))
+	if (static_key_false(&netstamp_needed))
 		__net_timestamp(skb);
 }
 
 #define net_timestamp_check(COND, SKB)			\
-	if (static_branch(&netstamp_needed)) {		\
+	if (static_key_false(&netstamp_needed)) {		\
 		if ((COND) && !(SKB)->tstamp.tv64)	\
 			__net_timestamp(SKB);		\
 	}						\
@@ -2660,7 +2660,7 @@ EXPORT_SYMBOL(__skb_get_rxhash);
 struct rps_sock_flow_table __rcu *rps_sock_flow_table __read_mostly;
 EXPORT_SYMBOL(rps_sock_flow_table);
 
-struct jump_label_key rps_needed __read_mostly;
+struct static_key rps_needed __read_mostly;
 
 static struct rps_dev_flow *
 set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
@@ -2945,7 +2945,7 @@ int netif_rx(struct sk_buff *skb)
 
 	trace_netif_rx(skb);
 #ifdef CONFIG_RPS
-	if (static_branch(&rps_needed))	{
+	if (static_key_false(&rps_needed)) {
 		struct rps_dev_flow voidflow, *rflow = &voidflow;
 		int cpu;
 
@@ -3309,7 +3309,7 @@ int netif_receive_skb(struct sk_buff *skb)
 		return NET_RX_SUCCESS;
 
 #ifdef CONFIG_RPS
-	if (static_branch(&rps_needed)) {
+	if (static_key_false(&rps_needed)) {
 		struct rps_dev_flow voidflow, *rflow = &voidflow;
 		int cpu, ret;
 
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index a1727cda03d7..495586232aa1 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -608,10 +608,10 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue,
 	spin_unlock(&rps_map_lock);
 
 	if (map)
-		jump_label_inc(&rps_needed);
+		static_key_slow_inc(&rps_needed);
 	if (old_map) {
 		kfree_rcu(old_map, rcu);
-		jump_label_dec(&rps_needed);
+		static_key_slow_dec(&rps_needed);
 	}
 	free_cpumask_var(mask);
 	return len;
diff --git a/net/core/sock.c b/net/core/sock.c
index 3e81fd2e3c75..3a4e5817a2a7 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -111,7 +111,7 @@
 #include <linux/init.h>
 #include <linux/highmem.h>
 #include <linux/user_namespace.h>
-#include <linux/jump_label.h>
+#include <linux/static_key.h>
 #include <linux/memcontrol.h>
 
 #include <asm/uaccess.h>
@@ -184,7 +184,7 @@ void mem_cgroup_sockets_destroy(struct cgroup *cgrp, struct cgroup_subsys *ss)
 static struct lock_class_key af_family_keys[AF_MAX];
 static struct lock_class_key af_family_slock_keys[AF_MAX];
 
-struct jump_label_key memcg_socket_limit_enabled;
+struct static_key memcg_socket_limit_enabled;
 EXPORT_SYMBOL(memcg_socket_limit_enabled);
 
 /*
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index d05559d4d9cd..0c2850874254 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -69,9 +69,9 @@ static int rps_sock_flow_sysctl(ctl_table *table, int write,
 		if (sock_table != orig_sock_table) {
 			rcu_assign_pointer(rps_sock_flow_table, sock_table);
 			if (sock_table)
-				jump_label_inc(&rps_needed);
+				static_key_slow_inc(&rps_needed);
 			if (orig_sock_table) {
-				jump_label_dec(&rps_needed);
+				static_key_slow_dec(&rps_needed);
 				synchronize_rcu();
 				vfree(orig_sock_table);
 			}