jump label: Introduce static_branch() interface

Introduce:

static __always_inline bool static_branch(struct jump_label_key *key);

instead of the old JUMP_LABEL(key, label) macro.

In this way, jump labels become really easy to use:

Define:

        struct jump_label_key jump_key;

Can be used as:

        if (static_branch(&jump_key))
                do unlikely code

enable/disale via:

        jump_label_inc(&jump_key);
        jump_label_dec(&jump_key);

that's it!

For the jump labels disabled case, the static_branch() becomes an
atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(),
atomic_dec() operations. We show testing results for this change below.

Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct.

Since we now require a 'struct jump_label_key *key', we can store a pointer into
the jump table addresses. In this way, we can enable/disable jump labels, in
basically constant time. This change allows us to completely remove the previous
hashtable scheme. Thanks to Peter Zijlstra for this re-write.

Testing:

I ran a series of 'tbench 20' runs 5 times (with reboots) for 3
configurations, where tracepoints were disabled.

jump label configured in
avg: 815.6

jump label *not* configured in (using atomic reads)
avg: 800.1

jump label *not* configured in (regular reads)
avg: 803.4

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110316212947.GA8792@redhat.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Suggested-by: H. Peter Anvin <hpa@linux.intel.com>
Tested-by: David Daney <ddaney@caviumnetworks.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

6 files changed, 44 insertions, 35 deletions

diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h
index 7622ccf75076..1881b316ca45 100644
--- a/arch/mips/include/asm/jump_label.h
+++ b/arch/mips/include/asm/jump_label.h
@@ -20,16 +20,18 @@
 #define WORD_INSN ".word"
 #endif
 
-#define JUMP_LABEL(key, label)                                          \
-        do {                                                            \
-                asm goto("1:\tnop\n\t"                                  \
-                        "nop\n\t"                                       \
-                        ".pushsection __jump_table,  \"a\"\n\t"         \
-                        WORD_INSN " 1b, %l[" #label "], %0\n\t"         \
-                        ".popsection\n\t"                               \
-                        : :  "i" (key) :  : label);                     \
-        } while (0)
-
+static __always_inline bool arch_static_branch(struct jump_label_key *key)
+{
+        asm goto("1:\tnop\n\t"
+                "nop\n\t"
+                ".pushsection __jump_table,  \"aw\"\n\t"
+                WORD_INSN " 1b, %l[l_yes], %0\n\t"
+                ".popsection\n\t"
+                : :  "i" (key) : : l_yes);
+        return false;
+l_yes:
+        return true;
+}
 
 #endif /* __KERNEL__ */
 
diff --git a/arch/sparc/include/asm/jump_label.h b/arch/sparc/include/asm/jump_label.h
index 427d4684e0d2..fc73a82366f8 100644
--- a/arch/sparc/include/asm/jump_label.h
+++ b/arch/sparc/include/asm/jump_label.h
@@ -7,17 +7,20 @@
 
 #define JUMP_LABEL_NOP_SIZE 4
 
-#define JUMP_LABEL(key, label)                                  \
-        do {                                                    \
-                asm goto("1:\n\t"                               \
-                         "nop\n\t"                              \
-                         "nop\n\t"                              \
-                         ".pushsection __jump_table,  \"a\"\n\t"\
-                         ".align 4\n\t"                         \
-                         ".word 1b, %l[" #label "], %c0\n\t"    \
-                         ".popsection \n\t"                     \
-                         : :  "i" (key) :  : label);\
-        } while (0)
+static __always_inline bool arch_static_branch(struct jump_label_key *key)
+{
+                asm goto("1:\n\t"
+                         "nop\n\t"
+                         "nop\n\t"
+                         ".pushsection __jump_table,  \"aw\"\n\t"
+                         ".align 4\n\t"
+                         ".word 1b, %l[l_yes], %c0\n\t"
+                         ".popsection \n\t"
+                         : :  "i" (key) : : l_yes);
+        return false;
+l_yes:
+        return true;
+}
 
 #endif /* __KERNEL__ */
 
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 13009d1af99a..8cdd1e247975 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -4,7 +4,6 @@
 #include <linux/types.h>
 #include <linux/stddef.h>
 #include <linux/stringify.h>
-#include <linux/jump_label.h>
 #include <asm/asm.h>
 
 /*
@@ -191,7 +190,7 @@ extern void *text_poke(void *addr, const void *opcode, size_t len);
 extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
 extern void text_poke_smp_batch(struct text_poke_param *params, int n);
 
-#if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
+#if defined(CONFIG_DYNAMIC_FTRACE) || defined(CONFIG_JUMP_LABEL)
 #define IDEAL_NOP_SIZE_5 5
 extern unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
 extern void arch_init_ideal_nop5(void);
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 574dbc22893a..f217cee86533 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -5,20 +5,24 @@
 
 #include <linux/types.h>
 #include <asm/nops.h>
+#include <asm/asm.h>
 
 #define JUMP_LABEL_NOP_SIZE 5
 
-# define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
-
-# define JUMP_LABEL(key, label)                                 \
-        do {                                                    \
-                asm goto("1:"                                   \
-                        JUMP_LABEL_INITIAL_NOP                  \
-                        ".pushsection __jump_table,  \"aw\" \n\t"\
-                        _ASM_PTR "1b, %l[" #label "], %c0 \n\t" \
-                        ".popsection \n\t"                      \
-                        : :  "i" (key) :  : label);             \
-        } while (0)
+#define JUMP_LABEL_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
+
+static __always_inline bool arch_static_branch(struct jump_label_key *key)
+{
+        asm goto("1:"
+                JUMP_LABEL_INITIAL_NOP
+                ".pushsection __jump_table,  \"aw\" \n\t"
+                _ASM_PTR "1b, %l[l_yes], %c0 \n\t"
+                ".popsection \n\t"
+                : :  "i" (key) : : l_yes);
+        return false;
+l_yes:
+        return true;
+}
 
 #endif /* __KERNEL__ */
 
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 4a234677e213..651454b0c811 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -679,7 +679,7 @@ void __kprobes text_poke_smp_batch(struct text_poke_param *params, int n)
         __stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
 }
 
-#if defined(CONFIG_DYNAMIC_FTRACE) || defined(HAVE_JUMP_LABEL)
+#if defined(CONFIG_DYNAMIC_FTRACE) || defined(CONFIG_JUMP_LABEL)
 
 #ifdef CONFIG_X86_64
 unsigned char ideal_nop5[5] = { 0x66, 0x66, 0x66, 0x66, 0x90 };
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index ab23f1ad4bf1..52f256f2cc81 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -24,6 +24,7 @@
 #include <linux/bug.h>
 #include <linux/mm.h>
 #include <linux/gfp.h>
+#include <linux/jump_label.h>
 
 #include <asm/system.h>
 #include <asm/page.h>