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 static void once_deferred(struct work_struct *w) 13 { 14 struct once_work *work; 15 16 work = container_of(w, struct once_work, work); 17 BUG_ON(!static_key_enabled(work->key)); 18 static_branch_disable(work->key); 19 kfree(work); 20 } 21 22 static void once_disable_jump(struct static_key_true *key) 23 { 24 struct once_work *w; 25 26 w = kmalloc(sizeof(*w), GFP_ATOMIC); 27 if (!w) 28 return; 29 30 INIT_WORK(&w->work, once_deferred); 31 w->key = key; 32 schedule_work(&w->work); 33 } 34 35 static DEFINE_SPINLOCK(once_lock); 36 37 bool __do_once_start(bool *done, unsigned long *flags) 38 __acquires(once_lock) 39 { 40 spin_lock_irqsave(&once_lock, *flags); 41 if (*done) { 42 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 __acquire(once_lock); 48 return false; 49 } 50 51 return true; 52 } 53 EXPORT_SYMBOL(__do_once_start); 54 55 void __do_once_done(bool *done, struct static_key_true *once_key, 56 unsigned long *flags) 57 __releases(once_lock) 58 { 59 *done = true; 60 spin_unlock_irqrestore(&once_lock, *flags); 61 once_disable_jump(once_key); 62 } 63 EXPORT_SYMBOL(__do_once_done); 64