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>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 91c1c8baf020..dcde2d9268cd 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -55,7 +55,7 @@
 #include <linux/uaccess.h>
 #include <linux/memcontrol.h>
 #include <linux/res_counter.h>
-#include <linux/jump_label.h>
+#include <linux/static_key.h>
 
 #include <linux/filter.h>
 #include <linux/rculist_nulls.h>
@@ -924,13 +924,13 @@ inline void sk_refcnt_debug_release(const struct sock *sk)
 #endif /* SOCK_REFCNT_DEBUG */
 
 #if defined(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) && defined(CONFIG_NET)
-extern struct jump_label_key memcg_socket_limit_enabled;
+extern struct static_key memcg_socket_limit_enabled;
 static inline struct cg_proto *parent_cg_proto(struct proto *proto,
 					       struct cg_proto *cg_proto)
 {
 	return proto->proto_cgroup(parent_mem_cgroup(cg_proto->memcg));
 }
-#define mem_cgroup_sockets_enabled static_branch(&memcg_socket_limit_enabled)
+#define mem_cgroup_sockets_enabled static_key_false(&memcg_socket_limit_enabled)
 #else
 #define mem_cgroup_sockets_enabled 0
 static inline struct cg_proto *parent_cg_proto(struct proto *proto,