From c5905afb0ee6550b42c49213da1c22d67316c194 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 24 Feb 2012 08:31:31 +0100 Subject: 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 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 Acked-by: Jason Baron Acked-by: Steven Rostedt Cc: a.p.zijlstra@chello.nl Cc: mathieu.desnoyers@efficios.com Cc: davem@davemloft.net Cc: ddaney.cavm@gmail.com Cc: Linus Torvalds Link: http://lkml.kernel.org/r/20120222085809.GA26397@elte.hu Signed-off-by: Ingo Molnar --- kernel/sched/sched.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'kernel/sched/sched.h') diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 98c0c2623db8..b4cd6d8ea150 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -611,7 +611,7 @@ static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu) * Tunables that become constants when CONFIG_SCHED_DEBUG is off: */ #ifdef CONFIG_SCHED_DEBUG -# include +# include # define const_debug __read_mostly #else # define const_debug const @@ -630,18 +630,18 @@ enum { #undef SCHED_FEAT #if defined(CONFIG_SCHED_DEBUG) && defined(HAVE_JUMP_LABEL) -static __always_inline bool static_branch__true(struct jump_label_key *key) +static __always_inline bool static_branch__true(struct static_key *key) { - return likely(static_branch(key)); /* Not out of line branch. */ + return static_key_true(key); /* Not out of line branch. */ } -static __always_inline bool static_branch__false(struct jump_label_key *key) +static __always_inline bool static_branch__false(struct static_key *key) { - return unlikely(static_branch(key)); /* Out of line branch. */ + return static_key_false(key); /* Out of line branch. */ } #define SCHED_FEAT(name, enabled) \ -static __always_inline bool static_branch_##name(struct jump_label_key *key) \ +static __always_inline bool static_branch_##name(struct static_key *key) \ { \ return static_branch__##enabled(key); \ } @@ -650,7 +650,7 @@ static __always_inline bool static_branch_##name(struct jump_label_key *key) \ #undef SCHED_FEAT -extern struct jump_label_key sched_feat_keys[__SCHED_FEAT_NR]; +extern struct static_key sched_feat_keys[__SCHED_FEAT_NR]; #define sched_feat(x) (static_branch_##x(&sched_feat_keys[__SCHED_FEAT_##x])) #else /* !(SCHED_DEBUG && HAVE_JUMP_LABEL) */ #define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x)) -- cgit v1.2.3