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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 /include/linux/static_key.h
parent1cfa60dc7d7c7cc774a44eee47ff135a644a1f31 (diff)
downloadop-kernel-dev-c5905afb0ee6550b42c49213da1c22d67316c194.zip
op-kernel-dev-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 'include/linux/static_key.h')
-rw-r--r--include/linux/static_key.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/static_key.h b/include/linux/static_key.h
new file mode 100644
index 0000000..27bd3f8
--- /dev/null
+++ b/include/linux/static_key.h
@@ -0,0 +1 @@
+#include <linux/jump_label.h>
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