mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-23 05:43:47 +07:00
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>
43 lines
749 B
C
43 lines
749 B
C
#ifndef _ASM_X86_JUMP_LABEL_H
|
|
#define _ASM_X86_JUMP_LABEL_H
|
|
|
|
#ifdef __KERNEL__
|
|
|
|
#include <linux/types.h>
|
|
#include <asm/nops.h>
|
|
#include <asm/asm.h>
|
|
|
|
#define JUMP_LABEL_NOP_SIZE 5
|
|
|
|
#define STATIC_KEY_INITIAL_NOP ".byte 0xe9 \n\t .long 0\n\t"
|
|
|
|
static __always_inline bool arch_static_branch(struct static_key *key)
|
|
{
|
|
asm goto("1:"
|
|
STATIC_KEY_INITIAL_NOP
|
|
".pushsection __jump_table, \"aw\" \n\t"
|
|
_ASM_ALIGN "\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__ */
|
|
|
|
#ifdef CONFIG_X86_64
|
|
typedef u64 jump_label_t;
|
|
#else
|
|
typedef u32 jump_label_t;
|
|
#endif
|
|
|
|
struct jump_entry {
|
|
jump_label_t code;
|
|
jump_label_t target;
|
|
jump_label_t key;
|
|
};
|
|
|
|
#endif
|