once.c (1555B)
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 8struct once_work { 9 struct work_struct work; 10 struct static_key_true *key; 11 struct module *module; 12}; 13 14static 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 25static 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 40static DEFINE_SPINLOCK(once_lock); 41 42bool __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} 58EXPORT_SYMBOL(__do_once_start); 59 60void __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} 68EXPORT_SYMBOL(__do_once_done);