Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : #include <linux/slab.h>
       3             : #include <linux/spinlock.h>
       4             : #include <linux/once.h>
       5             : #include <linux/random.h>
       6             : 
       7             : struct once_work {
       8             :         struct work_struct work;
       9             :         struct static_key_true *key;
      10             : };
      11             : 
      12           2 : static void once_deferred(struct work_struct *w)
      13             : {
      14           2 :         struct once_work *work;
      15             : 
      16           2 :         work = container_of(w, struct once_work, work);
      17           2 :         BUG_ON(!static_key_enabled(work->key));
      18           2 :         static_branch_disable(work->key);
      19           2 :         kfree(work);
      20           2 : }
      21             : 
      22           2 : static void once_disable_jump(struct static_key_true *key)
      23             : {
      24           2 :         struct once_work *w;
      25             : 
      26           2 :         w = kmalloc(sizeof(*w), GFP_ATOMIC);
      27           2 :         if (!w)
      28             :                 return;
      29             : 
      30           2 :         INIT_WORK(&w->work, once_deferred);
      31           2 :         w->key = key;
      32           2 :         schedule_work(&w->work);
      33             : }
      34             : 
      35             : static DEFINE_SPINLOCK(once_lock);
      36             : 
      37           7 : bool __do_once_start(bool *done, unsigned long *flags)
      38             :         __acquires(once_lock)
      39             : {
      40           7 :         spin_lock_irqsave(&once_lock, *flags);
      41           7 :         if (*done) {
      42           5 :                 spin_unlock_irqrestore(&once_lock, *flags);
      43             :                 /* Keep sparse happy by restoring an even lock count on
      44             :                  * this lock. In case we return here, we don't call into
      45             :                  * __do_once_done but return early in the DO_ONCE() macro.
      46             :                  */
      47           5 :                 __acquire(once_lock);
      48           5 :                 return false;
      49             :         }
      50             : 
      51             :         return true;
      52             : }
      53             : EXPORT_SYMBOL(__do_once_start);
      54             : 
      55           2 : void __do_once_done(bool *done, struct static_key_true *once_key,
      56             :                     unsigned long *flags)
      57             :         __releases(once_lock)
      58             : {
      59           2 :         *done = true;
      60           2 :         spin_unlock_irqrestore(&once_lock, *flags);
      61           2 :         once_disable_jump(once_key);
      62           2 : }
      63             : EXPORT_SYMBOL(__do_once_done);