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 --- arch/x86/include/asm/jump_label.h | 6 +++--- arch/x86/include/asm/paravirt.h | 6 +++--- arch/x86/kernel/kvm.c | 4 ++-- arch/x86/kernel/paravirt.c | 4 ++-- arch/x86/kvm/mmu_audit.c | 8 ++++---- 5 files changed, 14 insertions(+), 14 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index a32b18ce6ea..3a16c1483b4 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -9,12 +9,12 @@ #define JUMP_LABEL_NOP_SIZE 5 -#define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t" +#define STATIC_KEY_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t" -static __always_inline bool arch_static_branch(struct jump_label_key *key) +static __always_inline bool arch_static_branch(struct static_key *key) { asm goto("1:" - JUMP_LABEL_INITIAL_NOP + STATIC_KEY_INITIAL_NOP ".pushsection __jump_table, \"aw\" \n\t" _ASM_ALIGN "\n\t" _ASM_PTR "1b, %l[l_yes], %c0 \n\t" diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index a7d2db9a74f..c0180fd372d 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -230,9 +230,9 @@ static inline unsigned long long paravirt_sched_clock(void) return PVOP_CALL0(unsigned long long, pv_time_ops.sched_clock); } -struct jump_label_key; -extern struct jump_label_key paravirt_steal_enabled; -extern struct jump_label_key paravirt_steal_rq_enabled; +struct static_key; +extern struct static_key paravirt_steal_enabled; +extern struct static_key paravirt_steal_rq_enabled; static inline u64 paravirt_steal_clock(int cpu) { diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index f0c6fd6f176..694d801bf60 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -438,9 +438,9 @@ void __init kvm_guest_init(void) static __init int activate_jump_labels(void) { if (has_steal_clock) { - jump_label_inc(¶virt_steal_enabled); + static_key_slow_inc(¶virt_steal_enabled); if (steal_acc) - jump_label_inc(¶virt_steal_rq_enabled); + static_key_slow_inc(¶virt_steal_rq_enabled); } return 0; diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index d90272e6bc4..ada2f99388d 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -202,8 +202,8 @@ static void native_flush_tlb_single(unsigned long addr) __native_flush_tlb_single(addr); } -struct jump_label_key paravirt_steal_enabled; -struct jump_label_key paravirt_steal_rq_enabled; +struct static_key paravirt_steal_enabled; +struct static_key paravirt_steal_rq_enabled; static u64 native_steal_clock(int cpu) { diff --git a/arch/x86/kvm/mmu_audit.c b/arch/x86/kvm/mmu_audit.c index fe15dcc07a6..ea7b4fd3467 100644 --- a/arch/x86/kvm/mmu_audit.c +++ b/arch/x86/kvm/mmu_audit.c @@ -234,7 +234,7 @@ static void audit_vcpu_spte(struct kvm_vcpu *vcpu) } static bool mmu_audit; -static struct jump_label_key mmu_audit_key; +static struct static_key mmu_audit_key; static void __kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) { @@ -250,7 +250,7 @@ static void __kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) static inline void kvm_mmu_audit(struct kvm_vcpu *vcpu, int point) { - if (static_branch((&mmu_audit_key))) + if (static_key_false((&mmu_audit_key))) __kvm_mmu_audit(vcpu, point); } @@ -259,7 +259,7 @@ static void mmu_audit_enable(void) if (mmu_audit) return; - jump_label_inc(&mmu_audit_key); + static_key_slow_inc(&mmu_audit_key); mmu_audit = true; } @@ -268,7 +268,7 @@ static void mmu_audit_disable(void) if (!mmu_audit) return; - jump_label_dec(&mmu_audit_key); + static_key_slow_dec(&mmu_audit_key); mmu_audit = false; } -- cgit v1.2.3-70-g09d2