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once: switch to new jump label API

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Switch the DO_ONCE() macro from the deprecated jump label API to the new
one.  The new one is more readable, and for DO_ONCE() it also makes the
generated code more icache-friendly: now the one-time initialization
code is placed out-of-line at the jump target, rather than at the inline
fallthrough case.

Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Biggers 2017-10-09 14:30:52 -07:00 • committed by David S. Miller
parent d93fa2ba64
commit cf4c950b87
2 changed files with 7 additions and 7 deletions
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6
include/linux/once.h
View file

@ -5,7 +5,7 @@
#include <linux/jump_label.h> #include <linux/jump_label.h>
bool __do_once_start(bool *done, unsigned long *flags); bool __do_once_start(bool *done, unsigned long *flags);
void __do_once_done(bool *done, struct static_key *once_key, void __do_once_done(bool *done, struct static_key_true *once_key,
unsigned long *flags); unsigned long *flags);
/* Call a function exactly once. The idea of DO_ONCE() is to perform /* Call a function exactly once. The idea of DO_ONCE() is to perform
@ -38,8 +38,8 @@ void __do_once_done(bool *done, struct static_key *once_key,
({ \ ({ \
bool ___ret = false; \ bool ___ret = false; \
static bool ___done = false; \ static bool ___done = false; \
static struct static_key ___once_key = STATIC_KEY_INIT_TRUE; \ static DEFINE_STATIC_KEY_TRUE(___once_key); \
if (static_key_true(&___once_key)) { \ if (static_branch_unlikely(&___once_key)) { \
unsigned long ___flags; \ unsigned long ___flags; \
___ret = __do_once_start(&___done, &___flags); \ ___ret = __do_once_start(&___done, &___flags); \
if (unlikely(___ret)) { \ if (unlikely(___ret)) { \

8
lib/once.c
View file

@ -5,7 +5,7 @@
struct once_work { struct once_work {
struct work_struct work; struct work_struct work;
struct static_key *key; struct static_key_true *key;
}; };
static void once_deferred(struct work_struct *w) static void once_deferred(struct work_struct *w)
@ -14,11 +14,11 @@ static void once_deferred(struct work_struct *w)
work = container_of(w, struct once_work, work); work = container_of(w, struct once_work, work);
BUG_ON(!static_key_enabled(work->key)); BUG_ON(!static_key_enabled(work->key));
static_key_slow_dec(work->key); static_branch_disable(work->key);
kfree(work); kfree(work);
} }
static void once_disable_jump(struct static_key *key) static void once_disable_jump(struct static_key_true *key)
{ {
struct once_work *w; struct once_work *w;
@ -51,7 +51,7 @@ bool __do_once_start(bool *done, unsigned long *flags)
} }
EXPORT_SYMBOL(__do_once_start); EXPORT_SYMBOL(__do_once_start);
void __do_once_done(bool *done, struct static_key *once_key, void __do_once_done(bool *done, struct static_key_true *once_key,
unsigned long *flags) unsigned long *flags)
__releases(once_lock) __releases(once_lock)
{ {