// SPDX-License-Identifier: GPL-2.0 #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_true *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_branch_disable(work->key); kfree(work); } static void once_disable_jump(struct static_key_true *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_true *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);