mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-27 22:53:55 +08:00
c90aeb9482
Make the get_random_once() helper generic enough, so that functions in general would only be called once, where one user of this is then net_get_random_once(). The only implementation specific call is to get_random_bytes(), all the rest of this *_once() facility would be duplicated among different subsystems otherwise. The new DO_ONCE() helper will be used by prandom() later on, but might also be useful for other scenarios/subsystems as well where a one-time initialization in often-called, possibly fast path code could occur. Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
58 lines
1.7 KiB
C
58 lines
1.7 KiB
C
#ifndef _LINUX_ONCE_H
|
|
#define _LINUX_ONCE_H
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/jump_label.h>
|
|
|
|
bool __do_once_start(bool *done, unsigned long *flags);
|
|
void __do_once_done(bool *done, struct static_key *once_key,
|
|
unsigned long *flags);
|
|
|
|
/* Call a function exactly once. The idea of DO_ONCE() is to perform
|
|
* a function call such as initialization of random seeds, etc, only
|
|
* once, where DO_ONCE() can live in the fast-path. After @func has
|
|
* been called with the passed arguments, the static key will patch
|
|
* out the condition into a nop. DO_ONCE() guarantees type safety of
|
|
* arguments!
|
|
*
|
|
* Not that the following is not equivalent ...
|
|
*
|
|
* DO_ONCE(func, arg);
|
|
* DO_ONCE(func, arg);
|
|
*
|
|
* ... to this version:
|
|
*
|
|
* void foo(void)
|
|
* {
|
|
* DO_ONCE(func, arg);
|
|
* }
|
|
*
|
|
* foo();
|
|
* foo();
|
|
*
|
|
* In case the one-time invocation could be triggered from multiple
|
|
* places, then a common helper function must be defined, so that only
|
|
* a single static key will be placed there!
|
|
*/
|
|
#define DO_ONCE(func, ...) \
|
|
({ \
|
|
bool ___ret = false; \
|
|
static bool ___done = false; \
|
|
static struct static_key ___once_key = STATIC_KEY_INIT_TRUE; \
|
|
if (static_key_true(&___once_key)) { \
|
|
unsigned long ___flags; \
|
|
___ret = __do_once_start(&___done, &___flags); \
|
|
if (unlikely(___ret)) { \
|
|
func(__VA_ARGS__); \
|
|
__do_once_done(&___done, &___once_key, \
|
|
&___flags); \
|
|
} \
|
|
} \
|
|
___ret; \
|
|
})
|
|
|
|
#define get_random_once(buf, nbytes) \
|
|
DO_ONCE(get_random_bytes, (buf), (nbytes))
|
|
|
|
#endif /* _LINUX_ONCE_H */
|