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authorIngo Molnar <mingo@elte.hu>2012-02-24 08:31:31 +0100
committerIngo Molnar <mingo@elte.hu>2012-02-24 10:05:59 +0100
commitc5905afb0ee6550b42c49213da1c22d67316c194 (patch)
tree253fdb322e6e5b257ffda3b9b66bce90a473a6f7 /kernel/tracepoint.c
parent1cfa60dc7d7c7cc774a44eee47ff135a644a1f31 (diff)
downloadvexpress-lsk-c5905afb0ee6550b42c49213da1c22d67316c194.tar.gz
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>
Diffstat (limited to 'kernel/tracepoint.c')
-rw-r--r--kernel/tracepoint.c20
1 files changed, 10 insertions, 10 deletions
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index f1539decd99..d96ba22dabf 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -25,7 +25,7 @@
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/sched.h>
-#include <linux/jump_label.h>
+#include <linux/static_key.h>
extern struct tracepoint * const __start___tracepoints_ptrs[];
extern struct tracepoint * const __stop___tracepoints_ptrs[];
@@ -256,9 +256,9 @@ static void set_tracepoint(struct tracepoint_entry **entry,
{
WARN_ON(strcmp((*entry)->name, elem->name) != 0);
- if (elem->regfunc && !jump_label_enabled(&elem->key) && active)
+ if (elem->regfunc && !static_key_enabled(&elem->key) && active)
elem->regfunc();
- else if (elem->unregfunc && jump_label_enabled(&elem->key) && !active)
+ else if (elem->unregfunc && static_key_enabled(&elem->key) && !active)
elem->unregfunc();
/*
@@ -269,10 +269,10 @@ static void set_tracepoint(struct tracepoint_entry **entry,
* is used.
*/
rcu_assign_pointer(elem->funcs, (*entry)->funcs);
- if (active && !jump_label_enabled(&elem->key))
- jump_label_inc(&elem->key);
- else if (!active && jump_label_enabled(&elem->key))
- jump_label_dec(&elem->key);
+ if (active && !static_key_enabled(&elem->key))
+ static_key_slow_inc(&elem->key);
+ else if (!active && static_key_enabled(&elem->key))
+ static_key_slow_dec(&elem->key);
}
/*
@@ -283,11 +283,11 @@ static void set_tracepoint(struct tracepoint_entry **entry,
*/
static void disable_tracepoint(struct tracepoint *elem)
{
- if (elem->unregfunc && jump_label_enabled(&elem->key))
+ if (elem->unregfunc && static_key_enabled(&elem->key))
elem->unregfunc();
- if (jump_label_enabled(&elem->key))
- jump_label_dec(&elem->key);
+ if (static_key_enabled(&elem->key))
+ static_key_slow_dec(&elem->key);
rcu_assign_pointer(elem->funcs, NULL);
}