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