forked from luck/tmp_suning_uos_patched
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>
63 lines
1.3 KiB
C
63 lines
1.3 KiB
C
#include <linux/slab.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/once.h>
|
|
#include <linux/random.h>
|
|
|
|
struct once_work {
|
|
struct work_struct work;
|
|
struct static_key *key;
|
|
};
|
|
|
|
static void once_deferred(struct work_struct *w)
|
|
{
|
|
struct once_work *work;
|
|
|
|
work = container_of(w, struct once_work, work);
|
|
BUG_ON(!static_key_enabled(work->key));
|
|
static_key_slow_dec(work->key);
|
|
kfree(work);
|
|
}
|
|
|
|
static void once_disable_jump(struct static_key *key)
|
|
{
|
|
struct once_work *w;
|
|
|
|
w = kmalloc(sizeof(*w), GFP_ATOMIC);
|
|
if (!w)
|
|
return;
|
|
|
|
INIT_WORK(&w->work, once_deferred);
|
|
w->key = key;
|
|
schedule_work(&w->work);
|
|
}
|
|
|
|
static DEFINE_SPINLOCK(once_lock);
|
|
|
|
bool __do_once_start(bool *done, unsigned long *flags)
|
|
__acquires(once_lock)
|
|
{
|
|
spin_lock_irqsave(&once_lock, *flags);
|
|
if (*done) {
|
|
spin_unlock_irqrestore(&once_lock, *flags);
|
|
/* Keep sparse happy by restoring an even lock count on
|
|
* this lock. In case we return here, we don't call into
|
|
* __do_once_done but return early in the DO_ONCE() macro.
|
|
*/
|
|
__acquire(once_lock);
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL(__do_once_start);
|
|
|
|
void __do_once_done(bool *done, struct static_key *once_key,
|
|
unsigned long *flags)
|
|
__releases(once_lock)
|
|
{
|
|
*done = true;
|
|
spin_unlock_irqrestore(&once_lock, *flags);
|
|
once_disable_jump(once_key);
|
|
}
|
|
EXPORT_SYMBOL(__do_once_done);
|