| 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 | #include <linux/module.h> |
| 7 | |
| 8 | struct once_work { |
| 9 | struct work_struct work; |
| 10 | struct static_key_true *key; |
| 11 | struct module *module; |
| 12 | }; |
| 13 | |
| 14 | static void once_deferred(struct work_struct *w) |
| 15 | { |
| 16 | struct once_work *work; |
| 17 | |
| 18 | work = container_of(w, struct once_work, work); |
| 19 | BUG_ON(!static_key_enabled(work->key)); |
| 20 | static_branch_disable(work->key); |
| 21 | module_put(work->module); |
| 22 | kfree(work); |
| 23 | } |
| 24 | |
| 25 | static void once_disable_jump(struct static_key_true *key, struct module *mod) |
| 26 | { |
| 27 | struct once_work *w; |
| 28 | |
| 29 | w = kmalloc(sizeof(*w), GFP_ATOMIC); |
| 30 | if (!w) |
| 31 | return; |
| 32 | |
| 33 | INIT_WORK(&w->work, once_deferred); |
| 34 | w->key = key; |
| 35 | w->module = mod; |
| 36 | __module_get(mod); |
| 37 | schedule_work(&w->work); |
| 38 | } |
| 39 | |
| 40 | static DEFINE_SPINLOCK(once_lock); |
| 41 | |
| 42 | bool __do_once_start(bool *done, unsigned long *flags) |
| 43 | __acquires(once_lock) |
| 44 | { |
| 45 | spin_lock_irqsave(&once_lock, *flags); |
| 46 | if (*done) { |
| 47 | spin_unlock_irqrestore(&once_lock, *flags); |
| 48 | /* Keep sparse happy by restoring an even lock count on |
| 49 | * this lock. In case we return here, we don't call into |
| 50 | * __do_once_done but return early in the DO_ONCE() macro. |
| 51 | */ |
| 52 | __acquire(once_lock); |
| 53 | return false; |
| 54 | } |
| 55 | |
| 56 | return true; |
| 57 | } |
| 58 | EXPORT_SYMBOL(__do_once_start); |
| 59 | |
| 60 | void __do_once_done(bool *done, struct static_key_true *once_key, |
| 61 | unsigned long *flags, struct module *mod) |
| 62 | __releases(once_lock) |
| 63 | { |
| 64 | *done = true; |
| 65 | spin_unlock_irqrestore(&once_lock, *flags); |
| 66 | once_disable_jump(once_key, mod); |
| 67 | } |
| 68 | EXPORT_SYMBOL(__do_once_done); |
| 69 | |
| 70 | static DEFINE_MUTEX(once_mutex); |
| 71 | |
| 72 | bool __do_once_sleepable_start(bool *done) |
| 73 | __acquires(once_mutex) |
| 74 | { |
| 75 | mutex_lock(&once_mutex); |
| 76 | if (*done) { |
| 77 | mutex_unlock(&once_mutex); |
| 78 | /* Keep sparse happy by restoring an even lock count on |
| 79 | * this mutex. In case we return here, we don't call into |
| 80 | * __do_once_done but return early in the DO_ONCE_SLEEPABLE() macro. |
| 81 | */ |
| 82 | __acquire(once_mutex); |
| 83 | return false; |
| 84 | } |
| 85 | |
| 86 | return true; |
| 87 | } |
| 88 | EXPORT_SYMBOL(__do_once_sleepable_start); |
| 89 | |
| 90 | void __do_once_sleepable_done(bool *done, struct static_key_true *once_key, |
| 91 | struct module *mod) |
| 92 | __releases(once_mutex) |
| 93 | { |
| 94 | *done = true; |
| 95 | mutex_unlock(&once_mutex); |
| 96 | once_disable_jump(once_key, mod); |
| 97 | } |
| 98 | EXPORT_SYMBOL(__do_once_sleepable_done); |