mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 10:49:33 +00:00
c5905afb0e
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>
37 lines
665 B
C
37 lines
665 B
C
#ifndef _ASM_S390_JUMP_LABEL_H
|
|
#define _ASM_S390_JUMP_LABEL_H
|
|
|
|
#include <linux/types.h>
|
|
|
|
#define JUMP_LABEL_NOP_SIZE 6
|
|
|
|
#ifdef CONFIG_64BIT
|
|
#define ASM_PTR ".quad"
|
|
#define ASM_ALIGN ".balign 8"
|
|
#else
|
|
#define ASM_PTR ".long"
|
|
#define ASM_ALIGN ".balign 4"
|
|
#endif
|
|
|
|
static __always_inline bool arch_static_branch(struct static_key *key)
|
|
{
|
|
asm goto("0: brcl 0,0\n"
|
|
".pushsection __jump_table, \"aw\"\n"
|
|
ASM_ALIGN "\n"
|
|
ASM_PTR " 0b, %l[label], %0\n"
|
|
".popsection\n"
|
|
: : "X" (key) : : label);
|
|
return false;
|
|
label:
|
|
return true;
|
|
}
|
|
|
|
typedef unsigned long jump_label_t;
|
|
|
|
struct jump_entry {
|
|
jump_label_t code;
|
|
jump_label_t target;
|
|
jump_label_t key;
|
|
};
|
|
|
|
#endif
|